PVC-U, PVC-O, and C-PVC pipe systems are completely safe for drinking water applications and have been used in such applications throughout Europe (and elsewhere) for many decades.
If you are looking for more details, kindly visit SINCO.
In Europe, the safety of PVC-U, PVC-O, and C-PVC pipe systems for the transportation of drinking water is currently regulated and assessed nationally, although significant effort is ongoing at the European level for the harmonisation of regulations and test methods. Regulations are presently determined by national bodies, and third-party certification is carried out by accredited laboratories and institutes who subsequently also carry out regular audits to ensure continued compliance.
As part of the harmonisation activities, European (EN) standards are under development for a number of test methods designed to assess the suitability of plastics pipe systems for drinking water. These standards include tests for organoleptic assessment (odour and flavour), the migration & leaching of substances into the water, and microbial growth.
Migration: Different methods are used to detect the migration of substances present in PVC-U, PVC-O, and C-PVC formulations. Leaching behaviour is assessed by prolonged direct contact of the potable water with the products in very severe conditions. Then the "migration water" is checked using different techniques, including searches for traces of molecules below the level of a few µg/l. Virtually nothing leaches out: the leachates are very similar to the blanks used when analysing them with techniques such as gas chromatography combined with mass spectroscopy (GC-MS).
Lead is not used anymore in stabilisers, and such stabilisers have never been a source of lead in drinking water, as the stabilisers are immobilised within the PVC pipe structure during the manufacturing process. New stabiliser systems being used as alternatives to lead are fully assessed ("positive listing") and do not affect the drinking water characteristics in any way.
Traces of vinyl chloride monomer, sometimes exceeding the regulatory limit of 0.5 µg of VCM/l of water, have been detected in some cases. It is important to keep in mind that this 0.5 µg/l limit is based on a guideline from the World Health Organisation (WHO), where the value has been set to guarantee an acceptable health risk, even in case of exposure during an entire lifetime.
These cases are related to exceptional circumstances (small diameter pipes in thinly populated regions, hence with intermittent flow). Most importantly, these cases appeared only in pipes installed before the s when the health risks of VCM were identified. PVC resin produced before then, although meeting all standards applicable at that time, contained higher levels of residual monomer than presently. Under usual conditions of use, water transported in PVC pipes produced in those days also complies today with the current drinking water regulation. However, model calculations show that in exceptional circumstances (small diameter pipes, infrequent use) the VCM level reached after a period without flow can exceed the limit. No measurement result above the limit has ever been found in water flowing in pipes made from PVC produced after .
It is important to stress that no vinyl chloride monomer is produced by the degradation or incineration of PVC products.
In any case, VCM concentration can easily be reduced to below the WHO guidance limit by flushing the pipe or by boiling the water. The high volatility of VCM leads to a rapid transfer from water into the atmosphere, where VCM degrades by reaction with photochemically produced substances naturally present in the atmosphere. This limits its half-life in the atmosphere to between a few hours and a few days. VCM is therefore not persistent in the environment.
Microbial growth: PVC-U, PVC-O, and C-PVC pipes are known to perform very well according to the different methods used in Europe for the assessment of microbial growth of products in contact with drinking water (Germany, United Kingdom, and The Netherlands). Many field studies confirm this good behaviour, which is linked to the absence of migration and the very good surface properties of these piping systems.
Odour & Flavour: Owing to the absence of migration and low bacterial growth in PVC-U, PVC-O, and C-PVC, the organoleptic properties of pipes made from these materials are generally very good, as confirmed by regular testing by different European institutes.
As part of the EU harmonisation process, EN standards include EN and EN for the assessment of organoleptic properties and water quality; CEN-TR for the prediction of migration using mathematical modelling; EN for assessing microbial growth; and EN for the GC-MS identification of water-leachable organic substances. Additionally, EN -1 is used for the organoleptic assessment of water in storage systems.
Apart from these standardisation initiatives, a European positive list for substances used in plastics materials in contact with drinking water is also under development. This harmonised EU positive list will eventually replace several existing national drinking water positive lists. Further guidance can be found in ISO TR .
European Commission. (). Commission Implementing Decision (EU) /367 of 23 January laying down rules for the application of Directive (EU) / of the European Parliament and of the Council by establishing the European positive lists of starting substances, compositions and constituents authorised for use in the manufacture of materials or products that come into contact with water intended for human consumption. EUR-Lex. Link
Zhang, L., & Liu, S. (). Investigation of organic compounds migration from polymeric pipes into drinking water under long retention times. Procedia Engineering, 70, –. Link
Van der Kooij, D., & Veenendaal, H. R. (). Assessment of the microbial growth potential of materials in contact with treated water intended for human consumption. Kiwa Water Research. Link
Mercea, P. V., Losher, C., Benz, H., Petrasch, M., Costa, C., Stone, V. W., & Toșa, V. (). Migration of substances from unplasticized polyvinylchloride into drinking water: Estimation of conservative diffusion coefficients. Polymer Testing, 107, . Link
International Organization for Standardization. (). ISO/TR : Plastics pipes and fittings – Combined chemical-resistance classification table. ISO.
European Committee for Standardization. (). CEN/TR : Prediction of migration from plastics using mathematical modelling. CEN.
European Committee for Standardization. (). EN : Influence of materials on water for human consumption – Enhancement of microbial growth (EMG) test. CEN.
European Committee for Standardization. (). EN : Water quality – Gas chromatographic-mass spectrometric determination of water leachable organic substances (GC-MS). CEN.
European Committee for Standardization. (). EN -1: Influence of materials on water intended for human consumption – Organoleptic assessment of water in storage systems – Part 1: Test method. CEN.
European Parliament and Council of the European Union. (). Directive (EU) / of 16 December on the quality of water intended for human consumption (recast). EUR-Lex. Link
Danish Environmental Protection Agency. (). Field study of plastic pipes in water supplies (Environmental Project No. ). Link
European Commission. (). Commission Delegated Decision (EU) / of 11 March supplementing Directive (EU) / by laying down a methodology to measure microplastics in water intended for human consumption. EUR-Lex. Link
PVC pipes, including PVC-U, PVC-O, and C-PVC, are approved for use in potable water systems in many countries around the world. These pipes undergo rigorous standards and testing to ensure they do not contaminate the water they transport.
Migration & Leaching: PVC is utilised below its glass transition temperature (80°C). This acts as a functional barrier preventing any low molecular weight substances from migrating into drinking water. Migration tests have shown that migration levels are far below the detection limit of modern analytical techniques. Different methods assess the migration of substances present in PVC formulations. Leaching behaviour is evaluated by prolonged direct contact of potable water with the products under severe conditions. The "migration water" is then analysed using techniques like gas chromatography combined with mass spectroscopy (GC-MS). The results show that virtually nothing leaches out, and the leachates are very similar to the blanks used in the analysis.
Safety in Europe: PVC-U, PVC-O, and C-PVC pipe systems have been used safely for drinking water applications throughout Europe for many decades. The safety of these systems is currently regulated and assessed at the national level, although there's an ongoing effort at the European level for harmonisation of regulations and test methods. Accredited laboratories and institutes carry out third-party certification and regular audits to ensure continued compliance.
Stabilisers: Lead is no longer used in stabilisers, and such stabilisers have never been a source of lead in drinking water. The stabilisers are immobilised within the PVC pipe structure during manufacturing. New stabiliser systems being used as alternatives to lead do not affect drinking water characteristics.
Vinyl Chloride Monomer (VCM): Traces of VCM, sometimes exceeding the regulatory limit of 0.5 µg of VCM/l of water, have been detected in some cases. However, these cases are related to exceptional circumstances and only in pipes installed before the s. PVC pipes produced after have never shown measurements above the limit. It's important to note that no VCM is produced by the degradation or incineration of PVC products. VCM concentration can easily be reduced by flushing the pipe or boiling the water. VCM is not persistent in the environment.
Microbial Growth: PVC pipes perform exceptionally well in terms of microbial growth. This is due to the absence of migration and the excellent surface properties of these piping systems.
Odour & Flavour: Due to the absence of migration and low bacterial growth in PVC pipes, the organoleptic properties (related to taste and smell) of water transported in these pipes are generally very good.
European Standards: As part of the EU harmonisation process, several EN standards are under development or in use for assessing various properties of PVC pipes, including organoleptic properties, microbial growth, and migration.
Future Developments: A European positive list for substances used in plastics materials in contact with drinking water is under development. This list will eventually replace several existing national drinking water positive lists.
In conclusion, PVC pipes, when used and manufactured according to established standards, are safe for transporting drinking water and do not release carcinogenic substances into the water.
Mercea, P. V., Losher, C., Benz, H., Petrasch, M., Costa, C., Stone, V. W., & Toșa, V. (). Migration of substances from unplasticized polyvinylchloride into drinking water: Estimation of conservative diffusion coefficients. Polymer Testing, 107, . https://doi.org/10./j.polymertesting..
Zhang, L., & Liu, S. (). Investigation of organic compounds migration from polymeric pipes into drinking water under long retention times. Procedia Engineering, 70, –. https://doi.org/10./j.proeng..02.193
European Committee for Standardization. (). CEN/TR : Prediction of migration from plastics using mathematical modelling. CEN.
European Committee for Standardization. (). EN : Water quality – Gas chromatographic-mass spectrometric determination of water leachable organic substances (GC-MS). CEN.
European Commission. (). Commission Implementing Decision (EU) /367 of 23 January laying down rules for the application of Directive (EU) / of the European Parliament and of the Council by establishing the European positive lists of starting substances, compositions and constituents authorised for use in the manufacture of materials or products that come into contact with water intended for human consumption. EUR-Lex. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=OJ:L_
European Parliament and Council of the European Union. (). Directive (EU) / of 16 December on the quality of water intended for human consumption (recast). EUR-Lex. https://eur-lex.europa.eu/eli/dir///oj
European Commission. (). Commission Delegated Decision (EU) / of 11 March supplementing Directive (EU) / by laying down a methodology to measure microplastics in water intended for human consumption. EUR-Lex. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:D
The durability of PVC pipes is related, as it is for all other thermoplastic materials, to the chemical degradation of the polymer used in the pipes. However, unlike other thermoplastic pipes, PVC pipes do not oxidise.
Stabilisers are used in PVC pipes to prevent degradation of the polymer during the extrusion process and storage before the pipes are buried in the ground. When the pipes are buried, no chemical degradation is expected to occur, and the durability of the PVC material in buried pipes is expected to be significant, possibly exceeding years.
In standardised pipes for potable water (EN ), the expected lifetime of PVC pipes under pressure is extrapolated based on hoop stress testing for up to 20,000 hours. This allows an estimation of the durability by extrapolation to a life expectancy under pressure of 50 to 100 years. In real applications, buried PVC pressure pipes in Germany dug up after 70 years of active use were proven to still be fit for purpose when analysed and are likely to have a further life expectancy of 50 years.
A meta-study commissioned by TEPPFA, conducted by the Austrian Polymer Competence Centre at Montanuniversität Leoben, confirmed that plastic pipes, including PVC-U, can have safe service lifetimes well above 100 years. The study summarised significant independent research from peer-reviewed journals, standards, reports, and studies on pressure and non-pressure applications. The study found no evidence of material degradation in properly manufactured and installed pipes, suggesting that pipes made of PVC-U, polyethylene, and polypropylene can exceed a 100-year lifespan under operational conditions at a maximum of 20°C.
Notably, TEPPFA and PVC4Pipes also published a joint position paper supporting the 100-year design life of PVC-U and PVC-Hi pressure pipe systems buried in the ground for water and natural gas supply. These pipes, designed and tested to withstand long-term stress, are validated to maintain their integrity and performance well beyond 100 years when standard practices are followed during installation and operation.
In addition, to further increase the design life of PVC-U pipes, PVC4Pipes has sponsored a research project in collaboration with CEIS, led by Plastic Pipes Specialist Joaquin Lahoz Castillo. Launched in , this investigation focuses on demonstrating that PVC-U pressure pipes can be serviced for over 100 years. The study correlates processing temperatures with the long-term hydrostatic strength of the pipes, using ISO standards. Preliminary results indicate that an extrusion temperature of 180ºC is sufficient to achieve MRS250 classification. Higher temperatures, up to 195ºC, marginally improve long-term performance but risk material degradation. These findings enable water networks to be designed with a 100+ year lifespan, using standard design coefficients previously applied for 50-year systems.
Pinter, G., Travnicek, L., & Arbeiter, F. (). 100 years lifetime of plastic pipes: Meta-study. European Plastic Pipes and Fittings Association. https://www.teppfa.eu/wp-content/uploads/-04-25-Meta-study-100-years-of-lifetime-of-plastic-pipes.pdf
TEPPFA & PVC4Pipes. (). TEPPFA PVC4Pipes position paper for a 100-year service lifetime. https://pvc4pipes.com/wp-content/uploads//04/TEPPFA_PVC4Pipes-Position-Paper-for-a-100-years-service-lifetime-final.pdf
Lahoz Castillo, J. (). Securing a 100+ year design lifetime for PVC-U pressure pipes. CEIS.
PVC pipes and fittings are generally regarded as superior to other materials like vitrified clay (VC) and concrete (including both standard concrete and fiber-reinforced concrete, FRC) in terms of resistance to root intrusion. This superiority is attributed to the lower surface roughness and porosity of PVC, which significantly reduces the likelihood of roots penetrating through sealing joints. Studies have confirmed that PVC's smoother surfaces and tighter-fitting joints offer better protection against root intrusion compared to the rougher surfaces and more porous nature of VC and concrete pipes.
In comparison to concrete pipes, both standard and FRC, PVC pipes also demonstrate superior performance in preventing root intrusion. Concrete pipes, due to their rigid structure and tendency to crack over time, are more susceptible to root infiltration, especially at joints. Research has shown that concrete pipes experience more frequent root intrusions per joint compared to PVC pipes. Specifically, the mean number of root intrusions per joint for PVC pipes was significantly lower than that for concrete pipes. This makes PVC a preferable choice for minimizing the risk of root-related issues in sewer systems.
Despite PVC's advantages, it is important to recognize that these pipes are not completely immune to root intrusion. The performance of PVC pipes heavily depends on the quality of installation and maintenance. Proper bedding and installation are crucial to prevent vertical deformations and joint failures, which can increase the risk of root intrusion. For instance, improper installation can lead to vertical deformations and changes in pipe diameter, compromising the integrity of the joints and making them more susceptible to root intrusion.
The interfacial pressure at the joints of PVC pipes plays a critical role in preventing root intrusion. Research indicates that lower interfacial pressures (0.04–0.20 MPa) are associated with a higher likelihood of root intrusion. Therefore, it is recommended to maintain higher interfacial pressures, as specified by standards, to minimize the risk of roots penetrating the joints. Properly installed and maintained joints with adequate interfacial pressure help ensure the long-term effectiveness of PVC pipes in resisting root intrusion.
External factors such as soil type and environmental conditions also influence the performance of PVC pipes. For example, stiffer soils can help reduce deformations around the pipes, thereby maintaining the integrity of the joints more effectively. Conversely, in areas with softer soils, the pipes may experience more movement and deformation, leading to potential joint failures and increased susceptibility to root intrusion. Therefore, understanding and mitigating these external factors is essential for optimizing the performance of PVC pipes.
Long-term studies and CCTV inspections have shown that while PVC pipes generally perform well, issues such as root intrusion can still occur over time. Regular inspections and maintenance are necessary to identify and address potential problems early on. This proactive approach ensures the longevity and reliability of PVC sewer systems, helping to maintain their superior resistance to root intrusion.
Further studies, such as the research conducted on sewer pipes in Melbourne, have shown that soil disturbance during installation can create pathways for roots to grow from the surface towards the pipes. This is particularly true for well-drained sandy soils, which are conducive to deeper root growth. The Melbourne study highlighted that the majority of blockages occurred in sandy topsoils, emphasizing the need for proper installation and maintenance to prevent root intrusion.
Innovations in PVC pipe technology have further enhanced their resistance to root intrusion. A new pipe joining technology involves the creation of a lip-ring inside the socket during the manufacturing process. When the male pipe is inserted during installation, the lip-ring is pushed, closing the space between the male and female sewer pipes. This mechanical barrier effectively prevents the infiltration of roots. The new socket design has been certified for tightness by ISO -compliant lab tests and meets EN standards, further ensuring the reliability and durability of PVC pipes in preventing root intrusion.
In conclusion, PVC pipes offer significant advantages in terms of resistance to root intrusion compared to other materials like VC, standard concrete, and FRC. However, maintaining high interfacial pressures at the joints, ensuring proper installation, and conducting regular inspections are crucial to maximize their performance and durability. By addressing these factors, the long-term effectiveness of PVC pipes in preventing root intrusion can be significantly enhanced.
If you want to learn more, please visit our website Water Well UPVC Filter Pipe.
Makris, K. F., Langeveld, J., & Clemens, F. H. L. R. (). A review on the durability of PVC sewer pipes: research vs. practice. Structure and Infrastructure Engineering, 16(6), 880-897. https://doi.org/10./..
Östberg, J., Martinsson, M., Ståhl, O., & Fransson, A. M. (). Risk of root intrusion by tree and shrub species into sewer pipes in Swedish urban areas. Urban Forestry & Urban Greening, 11, 65-71. https://doi.org/10./j.ufug..11.004
Obradović, D. (). The impact of tree root systems on wastewater pipes. Zajednički Temelji '17: zbornik radova, 65-71. https://doi.org/10./-..
Randrup, T. (). Occurrence of tree roots in Danish municipal sewer systems. Arboricultural Journal, 24, 283-306. https://doi.org/10./..
Makris, K. F., Langeveld, J., & Clemens, F. H. L. R. (). A review on the durability of PVC sewer pipes: research vs. practice. Structure and Infrastructure Engineering, 16(6), 880-897. https://doi.org/10./..
Pohls, O., Bailey, N. G., & May, P. B. (). Study of Root Invasion of Sewer Pipes and Potential Ameliorative Techniques. Acta Horticulturae, 643, 113-121. https://doi.org/10./ActaHortic..643.17
IPM Srl. (, 7 October). Roots intrusion resistance: PVC pipes with patented system to prevent roots’ intrusion. https://www.ipm-italy.it/news-en/new-innovation/roots-intrusion-resistance
PVC pipes have been shown to offer significant environmental advantages over non-plastic materials like ductile iron and concrete, primarily in terms of carbon footprint and energy efficiency. Recent peer-reviewed research has demonstrated that, for sewer pipes, PVC outperforms reinforced concrete and ductile iron by reducing the carbon footprint by approximately 45% and 35%, respectively. This reduction is largely due to PVC’s lighter weight, which minimizes the energy required for production, transportation, and installation.
Moreover, PVC pipes consume less energy across their life cycle compared to other piping materials. Research from Australia confirms that, in all scenarios, PVC pipes require less energy than alternatives such as ductile iron or concrete. The life cycle of PVC pipes encompasses the energy consumed in the extraction of natural resources, manufacturing, transportation, and product delivery, consistently outperforming traditional materials.
Independent comparative Life Cycle Assessments (LCAs) conducted by the Flemish Institute for Technological Research (VITO) and reviewed by Denkstatt further confirm the low environmental impact of PVC pipes. These LCAs follow strict ISO standards (ISO , ISO ) and the European EN standard, ensuring that the environmental performance of PVC pipes is accurately measured. The assessments demonstrate that PVC pipes have the lowest environmental footprint compared to non-plastic materials in various piping applications.
The Environmental Product Declarations (EPDs) for PVC resin, based on data from Plastics Europe’s Eco-profile programme, highlight the efficiency of PVC production. The production of PVC requires less feedstock energy compared to other polymers, thanks to its 57% chlorine content derived from common salt. This results in a significantly lower environmental impact during production and use.
Recent advancements in PVC production processes have contributed to a steady reduction in environmental impacts. European chlorine production, a key component in PVC, has reduced its Global Warming Potential impact by 22.3% between and , thanks to innovations such as the switch to membrane electrolysis. These improvements directly benefit the overall environmental performance of PVC pipes.
In addition to its energy efficiency and reduced carbon footprint, PVC pipes are recyclable, further contributing to their eco-efficiency. Ongoing investments in innovation have led to the development of bio-attributed and bio-circular PVC resin and non-fossil additives, which are already being used in PVC pipe production. This aligns with the European PVC industry’s commitment to continual environmental improvement.
Overall, PVC pipes offer a more environmentally sustainable option compared to non-plastic materials like ductile iron and concrete. Their lower carbon footprint, energy efficiency, and recyclability make them a favorable choice for a wide range of piping applications.
Flemish Institute for Technological Research (VITO). (n.d.). Comparative Life Cycle Assessments for Plastic Pipes. European Plastic Pipe and Fittings Association (TEPPFA). https://www.teppfa.eu/sustainability
Plastics Europe (n.d.). Eco-profiles set. https://plasticseurope.org/ sustainability/circularity/life-cycle-thinking/eco-profiles-set/
McKinsey. (). Climate impact of plastics. https://www.mckinsey.com/industries/chemicals/our-insights/climate-impact-of-plastics
Meng, F., Brandão, M., & Cullen, J. M. (). Replacing plastics with alternatives is worse for greenhouse gas emissions in most cases. Environmental Science & Technology, 58(6), -. https://doi.org/10./acs.est.3c
Dioxins are a group of highly toxic chemicals that can be released as unintentional byproducts during various industrial processes. Dioxin emissions primarily occur as unintentional byproducts during certain industrial activities, such as waste incineration, metal smelting, and some chemical manufacturing processes, including the manufacturing of PVC.
While dioxins are a serious matter, the European case shows it is possible to solve this issue. Europe has significantly reduced dioxin emissions over the past few decades due to stricter regulations, improved technologies, and changes in industrial practices. This also applies to PVC, which today accounts for about 0.01% of the dioxins emitted from human activities in Europe.
The formation of very small quantities of dioxins can only occur during ethylene oxychlorination, which is one of the process steps leading to the production of vinyl chloride. These dioxin molecules are absorbed by the catalyst, which intervenes in a different phase from the reactants. This facilitates the removal of the catalyst and the absorbed dioxins by filtration and controlled treatment. Waste catalyst is handled as hazardous waste and disposed of accordingly.
The latest version of the ECVM Charter limits the emissions into the air of dioxin-like components from the vinyl chloride plants to 0.08 ng Toxic Equivalent (TEQ) per cubic meter of air. Emissions in water are limited to 0.3 µg per ton of ethylene dichloride produced. Ethylene dichloride is the intermediate leading to vinyl chloride. The emission limits of dioxins during manufacturing are aligned with the strict requirements in place in Europe and must be considered extremely low. To put this into context, 0.08 ng TEQ is equivalent to 0. grams of dioxin per cubic meter of air, and 0.3 µg is equivalent to 0. grams of dioxin per ton of ethylene dichloride produced in water.
Today, thermal processes in metal mining, metalworking, and other small sources have become the main contributors to dioxin emissions, according to the German Environment Agency.
ECVM. (). ECVM Industry Charter for the Production of Vinyl Chloride Monomer & PVC. Brussels, Belgium: The European Council of Vinyl Manufacturers. https://pvc.org/wp-content/uploads//04/ECVM-charter-pages.pdf
European Commission, Joint Research Centre. (). Best Available Techniques (BAT) Reference Document for Large Volume Organic Chemicals (LVOC) Production. https://eippcb.jrc.ec.europa.eu/sites/default/files/-11/JRC_LVOC_Bref.pdf
Umweltbundesamt [German Environment Agency]. (n.d.). Dioxins. https://www.umweltbundesamt.de/en/topics/chemicals/dioxins#what-are-dioxins-and-dioxine-like-pcbs
To keep loose sand and gravel from collapsing into the borehole, it is necessary to use well casing and screen. The screen supports the borehole walls while allowing water to enter the well; unslotted casing is placed above the screen to keep the rest of the borehole open and serve as a housing for pumping equipment. Since the well screen is the most important single factor affecting the efficiency of a well, it is sometimes called the "heart of the well"!
7.1 Screen Design
7.2 Screening Wells Drilled Into Rock
7.3 Screen Centralizers
7.4 Casing and Screen Installation
7.5 Solvent Welding (Gluing PVC)
7.6 Footnotes & references
7.1 Screen Design
Well screens should have as large a percentage of non-clogging slots as possible, be resistant to corrosion, have sufficient strength to resist collapse, be easily developed and prevent sand pumping (Driscoll, ). These characteristics are best met in commercial continuous-slot (wire wrap) screens consisting of a triangular-shaped wire wrapped around an array of rods (see Footnote #1). If these screens are available, conduct a sieve analysis on samples on the water-bearing formation and select a slot size which will retain 40-60 percent of the material.
While wire wrap screen should be used whenever possible, it may be exorbitantly expensive and/or not available. Most Lifewater wells are constructed using PVC casing and screen (Footnote #2) - see (Figure 9). Grey PVC pipe, which is available in most countries, is relatively cheap, corrosion resistant, lightweight, easy to work with and chemically inert.
Slot Design: Using a hack saw, cut slots in the plastic casing which are as long and close together as possible. Slots should be spaced as close together as possible vertically and should extend about 1/5th the circumference of the pipe; there should be 3 even rows of slots extending up the pipe separated by 3 narrower rows of solid, uncut pipe (for strength).
Figure 9: PVC Cut-Slotted Screen
Screen/Casing Diameter: Three inch diameter casing and screen can be easy inserted into the 15 cm (6 in) LS-100 borehole and allows creation of an effective 3 cm (1.25 in) thick filter pack (this is especially important where the aquifer is composed of very fine materials). However, since 7.6 cm (3 in) screen is often not available and has low total open area, carefully centered and filter packed 10 cm (4 in) screen is most frequently used. Larger diameter screens make the filter pack ineffective and do NOT significantly increase well yield. For example, moving from a 10 - 12.7 cm (4 - 5 in) screen will increase yield by 3 percent or less! Besides, a good filter pack expands the effective radius of the well to the full 15 cm (6 in) diameter of the borehole.
Screen Length: For confined aquifers, 80-90 percent of the thickness of the water-bearing zone should be screened (Driscoll, ). Best results are obtained by centring the screen section in the aquifer. For unconfined aquifers, maximum specific capacity is obtained by using the longest screen possible but more available drawdown results from using the shortest screen possible! These factors are optimized by screening the bottom 30-50 percent of the aquifer (Driscoll, ). One 7m (20ft) length of screen is often adequate. Screening 6-7 meters beneath the water table generally assures adequate year-round yield (Brush, 198?). In many tropical areas, successful wells can be constructed by drilling 5 feet into underlying rock and placing a 10 foot screen which straddles the bedrock/overburden interface (see Appendix C-4)Bottom Casing: Significant quantities of fine materials are often present in the extreme upper and lower parts of an aquifer. Therefore, unless the aquifer is less than 7 m thick, extend the casing at least 1-2 m into the top of the aquifer before starting the screen. Similarly, unless the aquifer is very thin, ensure that at least the bottom 1-2 meters of the aquifer is completed with a piece of solid casing pipe. This casing (known as a "sump" or "rat hole") provides a place for solids to settle as they are drawn into the well, thus minimizing screen blockage and minimizing the amount of fines drawn into the well (see Figure 9 and Section 9 - Figure 15).
Bottom Plug: A plug ("drive shoe") should always be installed to help the casing slip down the borehole and prevent unfiltered fines from entering the well. A cap or pointed wooden plug are the most common plugs. If "belled" casing (with a built-in socket on one end) is used, the non-belled end can be shaped into a point. Finally, a wash-down valve can be used or a one-way valve (allowing water to flow out of the casing) can be installed in a wooden plug which has a beveled inner surface (Figure 10). This valve allows the well to be effectively rinsed-out and ensures that the filter pack is effectively placed.
If any type of wooden plug is used, it is good practice to place a cement plug at the bottom of the well to ensure that sediment can not enter the well when the plug rots out. Put thick cement in thin plastic bags, drop them to the bottom of the well and then smash them open using drill pipe.
Figure 10: Wash-down Bottom Plugs
7.2 Screening Wells Drilled Into Rock
No casing or screen is generally required in the portion of boreholes drilled into rock. The first 2 - 3 m of the rock borehole should be 15 cm (6 in) in diameter; the borehole can then be extended using a 10 cm (4 in) bit (this maximizes the drilling speed which can be very slow in rock). The 11.4 cm (4.5 in) OD casing should be placed into the 15 cm (6 in) hole and carefully aligned with the (10 cm (4 in) hole. Fill the rock annular space with 40 cm coarse gravel followed by 60 cm coarse sand/fine gravel with 100 cm medium sand on top (this prevents fine sands and silts often found at the overburden-bedrock contact from moving into the well). Since the main water-bearing zone may be within the upper few inches of bedrock, only seal the casing into rock with cement where contamination is major concern.
7.3 Centralizers: Whenever possible, centralizers should be used on the outside of the rising main ("drop pipe") and on the pump rods. Adding centralizers minimizes the chance of pump rods banging against the rising main during operation of the handpump. This can be a serious problem in wells over 12.19 m (40 ft) deep since it eventually leads to early wearing-out of the rods and/or holes being rubbed in the rising main... leading to pump failure! Centralizers are also very important when installing casing since slots in the well screen may become severely blocked with clay if the screen rubs hard against the borehole wall while it is being inserted into the borehole. Centralizers also ensure that there is even distribution of cement grout and filter pack. This is really important since if the screen is placed against the borehole wall, the well may always produce turbid water! Poor grout placement can result in contaminated surface water entering the well and making the water unsafe to drink!These problems can be avoided by attaching (gluing, screwing, tying-on with wire) 3 centralizer strips to the top and bottom ends of the screen. Centralizers can be made from PVC casing, flexible green wood or 1.2 cm (0.5 in) wide iron straps (see Figure 11). Only fasten the lower end of each centralizer (so that it can "flex") and do not put any on the casing or the screen/casing may jamb during placement. Centralizers work best with 7.6 cm (3 in) casing; jamming may occur when installing 10 cm (4 in) casing in the 15 cm (6 in) borehole (the outside diameter of schedule 40 PVC pipe is 11.4 cm (4.5 in) and the diameter of couplings is 13.2 cm (5.2 in)! If this is a concern, just make the bottom plug the same diameter as the couplings.
Figure 11: Casing Centralizers
7.4 Casing and Screen Installation
Make sure you know the distance from the ground level to the bottom of the borehole and ensure that the required lengths of well casing and screen are prepared, clean, close at hand and ready to install when the drilling is completed. Attach the casing sump with the drive shoe to the bottom of well screen. For more information on solvent welding, see section 7.5. If bell and spigot pipe is not used, pre-glue a joining coupler (collar) to one end of each length of casing (see Figure 12).
Figure 12: Preparing Pipe for Installation
Once the borehole is completed to the desired depth, continue to circulate drilling fluid through the drill pipe at the bottom of the borehole until the returning fluids are clear of cuttings, sand, and clay balls. The fluid in the mud pits may need to be replaced several times before the water exiting the borehole is clean. When it is, keep the fluid circulating and the bit rotating and slowly remove the drill pipe from the borehole.
When the drill pipe is removed, swing the engine/drive assembly to the side. Prepare to clamp the casing using 2 grip clamps formed from iron or wood: 1 clamp should be on the casing suspended in the hole and the other on the length of casing to be joined (Figure 13). Alternatively, use a casing slip clamp made from 1/2 or 3/8 inch steel plate by cutting a slot slightly larger than the casing and welding on a handle (Figure 13).
Figure 13: Casing Clamps
Keeping the borehole full of water, carefully lower the screen assembly into the borehole. Ensure that a grip clamp is attached or use a slip clamp to catch the casing should it slip while being lowered. One at a time, wipe clean, add and glue 6 metre (full 20 foot) lengths of casing (see Section 7.5). If a slip clamp is used, wrap a 1 cm thick hemp rope 3-4 times around the upper length of casing (Figure 14) and keep it tight when pulling the clamp back to ensure that the casing can not slip. After the slip clamp is back in place, lessen the tension on the rope and allow the casing to slowly slip into the well until it is again resting on the clamp. Continue to add and lower casing until the well screen reaches the bottom of the borehole. Then raise it slightly and suspend it using grip clamps or by tying a rope to the drill table (this ensures that the casing is placed straight). Work quickly to minimize the chance that the borehole may start to collapse.
Figure 14: Rope Wrap Around Casing During Installation
Keep track of the length of screen and casing that is installed to ensure that the well has not partially caved-in (see Appendix G-2) and to ensure that the casing reaches the bottom of the borehole and is not stuck part way down the borehole (see Appendix G-10. Keeping the casing suspended 10 cm above the borehole bottom, cut the top off the casing so that only about 50 cm sticks-up above ground level (see Section 9 - Figure 15 and Section 14 - Figure 17).
After the casing is securely suspended, thoroughly flush the borehole again with clean water (this greatly reduces well development time (Section 10). If a one-way valve was installed at the bottom of the casing, run drill pipe down inside the casing until it is engaged in the top of the valve. If there is no valve, place a tight fitting surge block or securely wrapped rag on the end of the drill pipe. Then set the end of the drill pipe down to the bottom of the screen and pump clean water down the drill pipe so that it is forced out through the bottom section of screen. If these flushing processes are not possible, rinse-out the casing by connecting the mud pump outlet hose to the top of the casing by means of a well cap and appropriate fittings.
Finally, bail or pump out the casing. If it can be bailed practically dry, develop the full length of the screen several times (Section 10). Continue until no further improvement in yield is noticed. If there is not enough water (Section 10.3), remove the casing and abandon the well.
7.5 Solvent Welding
Solvent weld the pipe segments using the following procedure (NWWA, ):
1 They are strong, allow maximum flow rates and the small slot size screens-out fines. In addition, the screen is unlikely to plug-up over time since sand grains cannot plug slots which are V-shaped and widen inward and sand particles can only make contact at two points (Driscoll, ). Finally, the closely pitched, continuous slot facilitates uniform well development (Schreurs, 198?).
2 The disadvantages of using a locally manufactured screen when compared with commercial continuous wrap wire screens are:
Brush, R. (197?) "Wells Construction: Hand Dug and Hand Drilled", US Peace Corps, Washington DC.
Driscoll, F. () Groundwater and Wells, St. Paul: Johnson Division
National Water Well Association and Plastics Pipe Institute () Manual on the Selection and Installation of Thermoplastic Water Well Casing, Worthington, OH, 64pp.
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