Swimming pool pressure on bottom drain fittings

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Discussion Overview

The discussion revolves around the pressure experienced by the bottom drain fittings of an above ground swimming pool, specifically considering the effects of water depth and external soil conditions. Participants explore the implications of pressure on the fittings due to the weight of the water and the surrounding ground conditions.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about whether the pressure at the bottom drain fittings is ambient or greater due to the weight of the water.
  • Another participant states that pressure increases with depth, providing a calculation that suggests a pressure of 16.4 psi at the bottom of the pool.
  • A different viewpoint suggests that if the fittings are immersed in water, the pressure acts in all directions, resulting in a net force of zero on the fittings.
  • Concerns are raised about the force on the connection of a 1.5-inch diameter hose to the drain, emphasizing the pressure from the water at the bottom of the pool.
  • One participant argues that the external pressure on the fittings is dependent on ground conditions, noting that if the fitting is back-filled, it complicates the pressure assessment due to soil mechanics.
  • It is suggested that assuming ambient pressure outside the pipe is acceptable, provided the depth does not exceed about a foot.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the pressure acting on the fittings, with some asserting that the pressure is influenced by water depth while others emphasize the role of external ground conditions. The discussion remains unresolved regarding the exact pressures experienced by the fittings.

Contextual Notes

Limitations include the assumptions made about the external pressure and the conditions of the ground, which are not fully defined. The discussion also highlights the complexity of soil mechanics in relation to the pressure on the fittings.

rockie12_us
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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?

Thanks in advance
Dean-O
 
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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.
 
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.
 

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