Why is my spa draining when I turn off my pool pump?

PSC Ep. 79: Why is my spa draining when I turn off my pool pump?

In today’s episode of Poolside Chat, Rob and Matt tackle another common swimming pool question: 
Why is my spa draining when I turn off my pool pump?

Usually, the spa sits above the water line of the pool so if something goes wrong the water from the spa will drain out, but as to the cause as for why that would happen, the most common would be a check valve. There’s a check valve that helps keep the water in the spa and sometimes debris will get stuck in the check valve or the check valve will just go bad. In most cases you can open up the check valve and take a look at it, there are flapper style valves, you could just replace the flapper, or you might have to replace the whole thing. That’s the number one cause.

Some other reasons why there are diverter valves that control the spa suction if that’s left open or even partially open when the pump shuts off. It’s going to drain back out to the pool.

Within those diverter valves there’s a gate, and over time that gate could wear out, or the seal on that gate could become damaged so you might have to replace the internals in that valve. Another reason could be a bad actuator; maybe the actuator died when the gate was still left open on the suction side for the spa, so you’d have to replace that actuator.

Finally, you could have an air leak. Normally if a pool system is perfect, it’s sealed so that the water won’t drain out from the pump or anywhere else when it shuts off, but if there’s an air leak, it loses that seal and everything floods back to the pool. That’s another reason why your spa could drain out.


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7 thoughts on “PSC Ep. 79: Why is my spa draining when I turn off my pool pump?

  1. My Spa drains all the way down at about 2-3 inches a night until it drains to the bottom of the spa and then stops draining with the water in the drain cup only. It’s hard to tell if it is draining back in the pool. Your thoughts please

  2. Hi, my pool was draining all the water except maybe a foot of water, or until it reach the level of the pool water level when I turned off the pump..and yes I changed the check valve flapper… that worked for a couple of days…and yes it was draining back into the pool..what’s happening now is that the spa only drains like 10 inches at the most but what I’m noticing is that my pool is draining more than a few inches every day… if I divert the water from the spa and just have it circulate to the pool then the pool does not lose those inches of water…So I am assuming my pool does not have a leak…my question is if I change the check valve on the spa and the spa only loses a few inches and supposedly the water is supposed to drain back into the pool, I shouldn’t be losing so much water that my pool water level drops below the tiles…where is the water going?

    1. If you have checked all the valve, then it sounds like you have a leak in your spa. A spa shouldn’t lose 10 inches of water; plus, if your pool is affected as well then it definitely sounds like a leak. Because I can’t see your system or its plumbing, you may want to have a professional come out and take a look.

  3. My spa loses perhaps 3 to 5 inches overnight but stays above the jets which is approximately at pool level. The pool tech is confused because if it was a check valve normally it would lose water to a point of equalization with the level of the pool. Any ideas?

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