"EXT" writes:

Yes, it probably was because the 1 1/2" poly line was not perfectly flat as
it traveled 90 feet to the ditch. This is what happens when the final grade
was done 4 months later by a bulldozer and compressed the soil. However, I
have found that eliminating the check valve has eliminated any problems that
could be caused by using it: frozen discharge line and the check valve
sticking open. Using an air inlet valve was a simple and workable solution
for the past 36 years.

2 wrongs don't make a right.

But 3 "lefts" do.

I'd count yourself a lot luckier than smart about using a discharge
without positive slope and making it work by eliminating a check
valve.

Best Regards,
--
Todd H.
http://www.toddh.net/