State of Technology Report for Force Main Rehabilitation, Final ...

are, however, several communities (e.g., Charlotte-Mecklenberg) that have used epoxy lining extensively.
One of the limitations to epoxy lining for water mains has been the need to get NSF 61 certification. This
involves not only having the material certified, but also the delivery system as any unmixed or uncured
resin or hardener can pose a chemical hazard. There are over 41 companies which have their epoxy
products certified to NSF 61 as suitable for lining either water tanks and/or water mains (with diameter
restrictions). Not all of the listed resins are actively promoted for lining water mains. Some of the more
commonly used resins are similar to those used in the UK. A few examples of these products are listed
below:
• 3M Scotchkote 162 PWX
• Fyfe Company Tyfo PWC
• Hunting Industrial Coatings – Waterline
• Mercor Products – GeoPox GX 104
• NeoPoxy NPR-2000
• Nitoline
• NSP Specialty Products – NSP 120
• Raven Lining Systems – AquataPoxy A-6 and A-61
• Subterra - ELC
In 2007, the American Water Works Association (AWWA) standard AWWA C620 Spray-Applied In-
Place Epoxy Lining of Water Pipelines, 3-inch (75-mm) and Larger was published providing the first
national standard for epoxy lining. Up to this point, only a WRc guidance note was available. The epoxy
is a two-component material containing 100% solids by volume and must be capable of adhering to dry
and moist surfaces.
Prior to spin application of the epoxy, the host pipe’s interior surface must be free of corrosion byproducts,
deposits, loose and deteriorated coatings, oil, grease and accumulations of water, dirt and debris.
Power boring, drag cleaning, or abrasive pigging followed by foam swabbing is the preferred method of
preparing the inner surface.
For water main applications, one coat of epoxy with a minimum dry film thickness of 40 mils (1 mm) is
recommended. A dry film thickness of 80 mils (2 mm) is achievable and would be preferred for any
sewer force main applications given the higher corrosion potential offered by the effluent.
3.4.2.4 Polyurethane Spray-on Linings
Standard Polyurethane
Polyurethanes, which are a two-part poly-isocyanate, have virtually replaced the use of epoxy liners in the
UK. Polyurethane liners represent 80% of the UK market. They are applied using the exact same spin
equipment as epoxies. The thickness of the minimum dry film recommended is 40 mils (1 mm), the same
as epoxy, but the cure time is only 30 minutes. Consequently, the outage time for carrying out a
polyurethane lining operation can be less than 6 hours which, in a water distribution project, may negate
the need for any alternative water supply, thus saving money. The following polyurethane coatings are
approved by the DWI in the UK:
• 3M E. Wood Ltd – Scotchkote 169, Scotchkote 169HB, and Scotchkote 169LV
• Subterra – Fast-Line and Fast-Line Plus
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