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by Bill Nash
®UGlassIt Pool Resurfacing, Inc.
*How to Empty a
Fiberglass,
Gunite, or Concrete Swimming Pool Guide
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Every swimming pool built or
manufactured must, at one time or another, be emptied
for repair or resurfacing. There is no such thing as a
pool that will never need to be drained, regardless of
what you may have been led to believe.
With this in mind, almost every
type pool listed above has some method of relieving
the underground water pressure. This is a safety
feature built into pools to prevent the hydrostatic
pressure caused by underground water from damaging the
swimming pool. We are talking about serious damage, so
please take heed to the precautions I've listed.
Because fiberglass pools weigh
the least, as compared to concrete or gunite, the
danger of lifting is greater.
In my 15
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.
Never empty a fiberglass pool during the rainy season
unless the pool has a built-in system for relieving
the underground water pressure (which most do). If you
have standing ground water hours after it rains
anytime during the year, there is a strong possibility
that any pool (gunite or fiberglass) will lift.
Hydrostatic Relief Valves
If your concrete or gunite pool has hydrostatic relief valves
(usually located near the bottom of the steep slope), remove
them as soon as you can get to them while emptying the
pool. If you have an operating bottom drain, remove
the cover and see if it has a hydrostatic relief valve
(almost all do),
unscrew and remove the valve as
soon
as the
pool is drained.
The last foot or so of water probably won't drain out,
so be ready with a sump pump to immediately place at
the drain to remove the remaining water. This is
extremely important, and must be done quickly, so the
bottom drain can be accessed for removal of the cover.
Explanation of Swimming Pool Relief Valves
There are
three types of relief valves:
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Installed
Automatic Hydrostatic Relief Valves
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Installed
Removable Relief Valves
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New Relief
Valves for Installation
Automatic
relief valves are usually beneath the drain cover and
were installed when the pool was built. Occasionally,
they are installed by the pool owner sometime after the
pool was completed. In this instance, it may be
installed on the steep slope or on the bottom at the
deep end. More often than not, they do not work without
assistance. Time and climatic conditions are the source
of the problem. The high tech solution which I favor is
a whack with the handle of a screwdriver. If that
doesn't do it, hit it again. Invariably, it will perform
perfectly, after a little human kindness.
Installed
removable relief valves were either installed when the
drain was manufactured, or later, on the surface, by the
pool owner. These always work, but always need to be
opened manually. If it is original equipment and under
the drain cover, the valve cover can be pulled out after
removing two screws. The removable relief valves on the
surface are even easier to operate. Just unscrew the
recessed cap and the ground water will flow into the
pool where it can be later pumped out.
New relief
valves can be installed when necessary. We keep these in
stock and they are available for our customers use. We
provide the necessary instructions for installation.
Stand Pipe (fiberglass pools)
Many pools had a
water problem during construction and, to the current
owners good fortune, have an inconspicuous "stand-pipe"
located 2' to 30' from the pool. The pipe is less than
a foot high and may or may not have a cap. Place a long
hose into the pipe, then attach the hose to a utility
pump and drain the underground water. They can be
located near the diving board, near the pump and filter,
or anywhere else on the property.
Quite often, a stand
pipe equivalent was used when the pool was built, and a
high water table was encountered. You may have a piece
of black PVC emerging from the ground at the edge of the
concrete deck, in the grass. It should be slightly lower than the
top of the deck and usually goes unnoticed. This PVC goes directly into a 4' by 4'
pit filled with stone, and it's 4' deep.. This PVC serves the same function
as a stand-pipe, and should be used as explained above.
Well Points
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 pool or landscaping
contractor. Some pools
require well points only on one side or end, while others
must have well points around the entire pool.
These are general guidelines and are intended for
informational purposes for private, residential
pools only. The user shall assume all risks.
*This article may be reprinted
in its entirety with no omissions and with full credit to the author.
 ®
Pool Resurfacing, Inc.
67 Buck Road
Suite 140 Box B-43
Huntingdon Valley, PA 19006
Fiberglass resurfacing products for gunite, plaster, and concrete swimming pools plus gelcoat paint for fiberglass swimming pools now available in the US, Mexico, and the Caribbean!
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