On Tue, 3 Jun 2008 15:07:41 EDT, W Dale wrote:

Thanks Dave. I hope I never have that problem! Sounds like a real
head ache!
I do have a question though: How necessary is it to put cement around
the bottom drain to keep it from shifting? I have read a few tips on
installing them and they all say to put cement around the drain to
keep it from shifting and putting pressure on the liner. What are
your thoughts?

I'm not Dave, but I would like to offer my opinion about knife valves
and bottom drains. I have mostly knife valves, but also a couple ball
valves. I probably would agree if I were a few years younger and a
bit stronger, but ball valves have become a challenge to me and I
sometimes have to use an extension (Adjustable wrench, usually.) to
operate the handle. Knife valves otoh can be moved much easier with
fingers alone, even in difficult to reach places.. I must plan and
place the valves in a higher point on the line so a pebble doesn't
stop at that point.

When I installed a bottom drain, the instructions called for a 5/8"
gap around the perimeter of the drain dome/cover. That seemed
excessive, so I did some measuring and planning and set the gap
somewhat closer. I did a good job of packing in the clay, took
several days of wetting packing and checking. Bottom line, over the
years the drain did move slightly. Not enough to be a problem, but if
I were to do it again, I'd do the measuring, planning and pour
concrete around the pipe into a hole made in undisturbed clay, because
that is the better chance of it moving less. Pipe contact with the
earth is small compared to the amount of surface contact with the glob
of cement poured around the pipe.
--
Hal Middle Georgia, Zone 8
http://tinyurl.com/2fxzcb