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

Updated on January 7, 2018
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Rob is a licensed pool service industry professional with over 20 years of experience.

Pump off, spa water level dropping
Pump off, spa water level dropping | Source

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 water level of the pool. Normal operation (pool mode) of a pool/spa combination is that 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?

This is known as equalization. The level of the water in the spa 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. No water is being lost. Although not very noticeable, the pool actually receives the amount of water that has equalized from the spa.

"Check Valve"
"Check Valve" | Source

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 will allow the spa 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.

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) | Source

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.

© 2018 Rob Hampton


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