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Why Does My Spa Drain Down When the Pool Pump Shuts Off?

Rob is a pool-service industry professional with over 20 years of experience.

Pump off, spa water level dropping

Pump off, spa water level dropping

Is the Spa Leaking?

In most cases, it is unlikely that the spa is leaking if it drains down when the pump is off. If the spa is leaking, there would also be a noticeable drop in the pool's water level. In normal operation (pool mode) of a pool/spa combination, the spa is usually set to overflow into the pool, making a spa leak difficult to detect.

If It Doesn't Leak, Why Is It Draining?

If the spa's water level is higher than that of the pool, when the pump stops pushing water to the spa and pool, the spa will equalize itself to the level of the pool in a process known as equalization. No water is being lost. Although it's not very noticeable, the pool actually receives the amount of water that has equalized from the spa.

What Is Causing This, and Can It Be Fixed?

This can be fixed! The cause is what is known as a check valve. There may be either an existing check valve installed that needs replacing or no check valve at all. This valve uses a spring (or floater ball) inside it to allow the water to flow in only one direction. When the pump shuts off, water cannot flow back through the pool returns, which prevents the spa from equalizing and allow it to remain full. The parts inside of the valve can become worn over time, and in turn, cause it not to seal correctly after the pump and filter system times out. In this case, the check valve will need to be replaced.

"Check Valve"

"Check Valve"

More About Pool and Spa Combination Pools

A pool/spa combination pool uses the same water for both the spa and pool. Most use the same pump; some may have an added spa pump. Valve position is the main factor in determining where the water is flowing. The most common position for valves is to direct water to both the pool and spa in order to create a spa "overflow" or fountain effect when the spa is not in use. This is referred to as "spa spillover"

Many systems are now using automatic valves called "actuators" that are motorized and controlled by the touch of a button via an installed reception panel near the pump equipment and utilized by either an in-home remote or smart phone app to direct the valves into different modes. Lighting, heat and many other pool features can be activated using an automated system.

These valves are positioned for pool mode only. If the return valve was turned toward spa, this will create an overflow (fountain)

These valves are positioned for pool mode only. If the return valve was turned toward spa, this will create an overflow (fountain)

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: When the water is lowered from the spa, should I replace water in the spa before restarting the pool?

Answer: No, because in normal operation the spa main drain should be in the closed position already and the pump won't pull water from the spa.

© 2018 Rob Hampton

Comments

Rob Hampton (author) from Port Richey, Florida on June 29, 2019:

Hi Jorge.. It's difficult to say. There could be a leak somewhere on the overspill, or possibly leaking through the spa returns. Without seeing it, I can't really give a definitive answer.

Jorge on June 28, 2019:

What would be another reason for the water draining from spa into pool? I replace the check valve, purge all lines removing any air, check the jandy valves... yet my spa is still losing water to the pool. Any ideas?