Never empty a fiberglass pool during the rainy season.
If you have standing ground water hours after it rains
anytime during the year, there is a strong possibility
that the pool will lift. In my 11 years in this
industry, I’ve never had a fiberglass pool lift, however
two gunite pools did "pop". So the possibility certainly
exists. Use this information as a guide in an effort to
prevent this problem. The writer assumes no liability
for any damages to any swimming pool.
the Swimming Pool
There are two standard methods to
empty a pool
If you have a sand filter, buy a
backwash hose at your local pool supply store and attach
it to the valve on the filter.
If you do not have a sand filter,
then use a submersible pump (sump pump).
If using a backwash hose, keep a sump
handy to remove the last 6" or so of water. It is
imperative to remove these last few inches of water
immediately so the bottom drain cover can be removed.
This only applies to a center bottom drain which may
have a relief valve. There is no relief valve in a wall
mounted bottom drain, so the timing isn't relevant.
It is probably located under the bottom drain cover, and
it is probably stuck after all these years.
After using a sump
to remove the last six inches or so of water, pry (or unscrew) the drain cover off with a
screw driver and look inside. If there are two pipes
going out, you do have a hydrostatic relief valve. One
pipe goes to the pump, and the other goes underneath the
pool about two feet and ends.
Just a few
inches inside one of the pipes is the stuck valve.
Gently (at least at first) tap the valve with the handle
of a screwdriver. The underground water should begin to
Valve Follow the above directions and look inside
the drain. There will be one pipe going to the pump, and
a removable valve secured with two screws. Take out the
valve which releases the underground water.
Relief Drain Plug Some fiberglass pools
have a bottom drain plug with no attached plumbing. Just
unscrew the plug as soon as possible to enable the
underground water to flow into the pool. If there is no
flow of water, there is no reason for concern, at least
for the time being.
Some pools had a water
problem during construction and, to the current owners
good fortune, have a "stand-pipe" located near the pool.
If this is the case, simply remove the cap and place a
long pliable hose into the pipe, then attach the hose to
a utility pump and drain the underground water. This pvc pipe
goes directly into a french drain under the pool. A
french drain under the pool is usually 4' x 4' x 2'
deep, and filled with stones (size of drain and stones
The purpose of a stand
pipe is to drain the water that is under the pool.
This ground water is your pool's worst enemy. It can do
serious damage to your swimming pool when the pool water
level is too low. Never let anyone empty your swimming
pool, including a pool professional, without first
having a discussion about the stand pipe and the
hydrostatic relief valve. Never permit anyone to empty a
fiberglass swimming pool unless they can describe both
If you’re in a beach area or other low lying area, you
may need to consider “well points”, but this is a last
resort and is rarely necessary under other conditions.
When well points are necessary, they should be
installed by an experienced individual. Some pools
require well points only on one side, while others must
have well points around the entire pool.
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Fiberglass Pool Repair
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