(1) All plastic casing shall be installed only in an
oversized drill hole without driving. Wells cased with plastic shall have steel
casing extending a minimum of 18 feet below the surface and 18 inches above the
ground surface. Plastic casing to be used must be specifically designed for water
well construction and bears NSF approval. Methods of installation shall be:
(a) by installing a larger size steel
casing on the outside of the plastic casing with a minimum of 4 feet of overlap
(Figure 6A at the end of this sub-chapter) ; or
(b) by attaching directly to the plastic
casing a threaded plastic to steel coupling (Figure 6B) .
(2) Thermoplastic well casing shall conform
with American Society for Testing and Materials Specification F480-81 or latest
revision as follows:
(a) minimum standards dimension ratio shall
be 26 for inner casing in bedrock applications;
(b) minimum standards dimension ratio shall
be 21 for unconsolidated formations greater than 125 feet;
(c) minimum pipe stiffness shall be 224
foot-pounds/inē [kiloneutron (meter meter) ] when tested according to section
5.4.1 of American Society for Testing and Materials Specification F480;
(d) all casing 5 inches [12.7 centimeters]
and larger shall be tested for impact resistance and shall meet or exceed IC-1
impact classification according to section 6.5 and table 6 of American Society
for Testing and Materials Specification F480;
(e) carry the seal of the national
sanitation foundation.
(3) All casing shall have additional
thickness and weight if standard thickness is not capable of withstanding
forces to which it is subject.
(4) The well casing must be clearly marked
by the manufacturer showing: nominal size, type plastic material, standard
dimension ratio (SDR) , ASTM designation, and national sanitation foundation
seal of certified approval.
(5) The use of plastic well casing in connection with a pitless adaptor is not acceptable.