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 Post subject: Draining pool, water table question
PostPosted: March 20th, 2010, 8:12 am 
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Joined: June 2nd, 2007, 6:14 am
Posts: 67
Location: Annandale, VA
Hi;

Need to drain my 16x32 ig concrete pool to do some plaster and tile repairs. I've read up on the risk with high water tables and all. I live in Virginia and usually this time of the year (early spring) the ground is pretty wet. My yard slopes down, so 10' behind my pool the ground elevation is below the deep end of the pool. The retaining wall is designed to let water drain.

Is this a safe situation for draining since the water table is well below the pool? I would like to have the pool drained for a couple weeks as I plan to take care of a few different issues. Does a pool only float due to high water tables or are there other cases?

Lastly, and maybe most importantly, there's 4 "plugs" on the bottom, 2 in the shallow end and two in the deepend. They look like they unscrew. Are these meant to be unscrewed to relieve possible water pressure?

TIA,
Kevin



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 Post subject: Re: Draining pool, water table question
PostPosted: March 20th, 2010, 9:04 am 
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Joined: May 20th, 2007, 4:29 pm
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Location: South Central NJ
Are there hydrostatic plugs in the floor? If so, as they appear from under the lowing water, remove them.

Even though your wall lets water drain, your soil type will play a role in how much and how fast its drained or held. Heavy clay content soil holds water and slows draining while sandy soils drain quickly.

Do you know what the soil looks like down there? Do you have any pictures you could post from when the pool was being built?

Scott


P.S.- This is my 600th post!



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 Post subject: Re: Draining pool, water table question
PostPosted: March 20th, 2010, 11:20 am 
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It is unusual to have hydrostatic relief plugs, though not unheard of. I think that it is more likely that they are part of an abandoned in-floor cleaning system or a set of some other kind of deep returns.

Ground water is probably the only risk you need to worry about when draining a gunite pool in VA at this time of year. At the peak of summer there is a risk of expansion and contraction, caused by solar heating, cracking the plaster, however this is usually only an issue in hot dry climates (Arizona, Nevada, etc).



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 Post subject: Re: Draining pool, water table question
PostPosted: March 20th, 2010, 12:17 pm 
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Location: South Central NJ
Nearly all the gunite pools in my neck of the woods have 1.5" removable plugs specifically for hydrostatic relief when pools are emptied. Typically, there are two in the deep end and one near the top of the slope. If the homeowner has a high water table, it's not uncommon to find a dry well too. The rarity here is hydrostatic valves. I usually find them near a river or lake/reservoir.

Scott



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 Post subject: Re: Draining pool, water table question
PostPosted: March 20th, 2010, 2:18 pm 
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Joined: June 2nd, 2007, 6:14 am
Posts: 67
Location: Annandale, VA
I don't think the 4 valves are for a cleaning system. This pool is about 30 years old, built by Anthony Sulivan. Good pool over all. Anyways, as far as I know they didn't have in floor cleaning systems then.

When I drain the pool and remove one of these plugs what should I see? Assume an opening through the concrete and to the earth.

In virginia the soil does tend to have a lot of clay, depending on region.

Sorry, no picts.

Kevin



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16x32 Concrete IG, 20+ years old and going strong
Equipment: DE Filter, Jandy Gas Heater, Solar Panels, 1hp Hayward Pump, Aquarite SWG
Cleaners: Pool Buster Max Vacuum, Polaris 280 (replaced an Aquabot)
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 Post subject: Re: Draining pool, water table question
PostPosted: March 20th, 2010, 2:40 pm 
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Location: South Central NJ
I assume they have a cross pattern and are white . You may see dirt, gravel or water. Let the water in! I doubt there will be a lot. The ones in the deep end may have more.

Scott



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 Post subject: Re: Draining pool, water table question
PostPosted: March 20th, 2010, 2:55 pm 
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Joined: June 2nd, 2007, 6:14 am
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Location: Annandale, VA
Yup, white with a cross patern. Always wondered what they were there for. Awesome....now I can drain the pool with little worry. :lol:



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16x32 Concrete IG, 20+ years old and going strong
Equipment: DE Filter, Jandy Gas Heater, Solar Panels, 1hp Hayward Pump, Aquarite SWG
Cleaners: Pool Buster Max Vacuum, Polaris 280 (replaced an Aquabot)
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