Draining a fiberglass pool safely

SkipLynn

Active member
Aug 23, 2023
43
Arizona
Pool Size
15000
Surface
Fiberglass
Chlorine
Liquid Chlorine
How far down can you drain a fiberglass pool in Western Arizona? I am drawing due to the water being about 5 years old and am struggling with balancing the water chemistry. Is it better to drain halfway and then refill?
 
This is out of my wheelhouse. Just chiming in to let you know it was good to ask. The water is an integral part of the structure of any pool, but that is especially true for vinyl and fiberglass pools. In some cases, it is the water pressure being exerted on the fiberglass that is keeping the soil on the outside of the fiberglass in its place (particularly if the soil is saturated).

Others will chime in tomorrow about the engineering aspects of what you are asking about. In the meantime, read up on "No Drain Water Exchange." You might not have to lower the level of the water at all. Here is a good read for you:


Especially this section on that page:
No Drain Water Exchange
 
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Oh, and please post a full suite of test results. Do you have a proper test kit? Test Kits Compared

Our experts can use those test results to help you determine just how much water, if any, actually needs to be drained.
 
I drain mine completely. My soil is decomposed granite and does not move.

I have also done the no drain exchange. If followed correctly you can get a good exchange of water without draining.
 
Thanks for the advice, I’m gonna do the no drain exchange and monitor chemistry. Pool is 20 years old, and I don’t want to cause any problems that need to be fixed! I’m gonna do a modified no drain exchange exchange and drain it down about 2 feet (pool is 5’ deep) and then refill.
 
I’m gonna do a modified no drain exchange exchange and drain it down about 2 feet (pool is 5’ deep) and then refill.
You can do that. It will take about 3 times as much water that way. If you water is very cheap, go for it.