New Below Ground Pool

Construction or upgrading of new or existing
swimming pools. Pool building materials and
miscellaneous construction techniques.
Pool Newbie
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My Pool: One existing pool - one under construction

New Below Ground Pool

Postby rickyrt » Tue 13 Feb, 2018 04:31

Hi All,

I am in the process of constructing a new below ground pool in the Philippines about 70m from the coast.

I have already excavated 40% of the rock, going down to a depth of 1.75m for the deep end.

However at this depth I have hit seawater as this is the high tide water level and the ground is volcanic so lots of porous holes in the rock. An interesting thing I have noticed is the seawater level peaks two hours after high tide has happened - so some interesting drainage issues.

My question is - this is my second pool I have built here, first time to encounter sea water on land.

Anyone got any experience here? I have read about drainage channels of porous rock underneath and around the sides of the pool to ensure water will flow in case of water table issues.

My main concern is the corrosion aspect of building the base of the pool in saltwater as the pool will be 3m deep.

Also as a secondary question - does anyone have any rules of thumb for concrete thickness/rebars for pools in earthquake zones correlated with pool size so I can get real data to compare my analysis?

Swimming Pool Superstar
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My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: New Below Ground Pool

Postby Denniswiseman » Tue 13 Feb, 2018 08:08

I think you have a difficult project on your hands as twice a day you would be working in high tide sea water which would corrode any rebar and make it impossible for concrete laying
My initial thought would be to use a fibreglass shell but you would have to fill it as soon as you put it in the ground (very difficult)
My second thought would be to build it out of the ground so that the sea water won't affect it and then build up the ground
Drainage chanells would be a waste of time because at high tide there is nowhere for the sea water to go
I don't think a rule of thumb for earthquake zones is available, you would need a structural engineer
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My Pool: 12 x 24 (45m3) liner pool, Triton TR60 filter with AFM glass media (Activate) and variable speed pump running 0.08HP
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Re: New Below Ground Pool

Postby Teapot » Wed 14 Feb, 2018 03:32

Oh boy, I would open a beer and walk off into the sunset in the opposite direction.
I don't have enough free time to instruct you in how to build a pool that won't break.
I am out on this one.

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