# Swimming pool pressure on bottom drain fittings

## Main Question or Discussion Point

I have a practical question about my new above ground swimming pool that is 48 inches deep and 16 feet by 32 feet in width and length.

My question is, there is a bottom main drain that the water travels through to the filter/pump and is returned through the side return piping.

My question is. What is the pressure that the bottom main drains fitting connections see? Is it ambiant pressure or is it greater due to the weight of the water?

Dean-O

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russ_watters
Mentor
Pressure is a function of depth. The weight of a 1"x1" column of water 4 feet high is 1.7 lb, so the pessure (absolute) is 14.7+1.7=16.4 psi.

LURCH
If I understand your question correctly, the objects to which you refer are emersed in the water (no "dry side" to any of them), is this correct? If so, then the pressure Russ gaev you is acting in all directions, and the net force is 0.

But, if you're talking about a tube that comes out of the side fo your pool near the bottom, then the force trying to pop that tube loose is the water pressure at the bottom of the pool (16.4 PSI).

swimming pool drain

The bottom of the 4 foot deep pool has a drain, which connects to a 1.5 in diameter hose. My concern is the amount of force PSI, that this connection would see. The inside wall of the drain and fitting to the 1.5 diameter hose is in water the outside of the drain and the 1.5 hose is in the ground.

My understanding is that the objects are not immersed in water. The internal pressure will be as stated above.

The external pressure can't be easily determined as it depends on the conditions of the ground in which it is set. Normally a trench would be dug, the fitting inserted and it would be back-filled. This then becomes a probelm in granular flow and soil mechanics.

If you make the assumption that the pressure on the outside of the pipe is ambient then that should be OK, provided the depth into the ground does not exceed about a foot.