New Below Ground Pool

[rickyrt]

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?

[Denniswiseman]

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

[Teapot]

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.