Spa water level dropping when spa is in use

El Robbie

Member
Jul 31, 2018
9
Marietta, GA
EDIT: I think I've narrowed down the problem. See bottom of post.
I have a poolside spa that shares pump and plumbing with the in-ground pool. Normally water flows over the edge of the spa and into the pool. When the pool pump turns off, the spa remains full of water, as it should.
When the spa jets are turned on, automatic valves isolate the spa from the pool. The pump then draws water from the spa, optionally passes it through the heater, and returns it to the spa through the spa jets.
Recently when the spa jets are turned on, the water level in the spa begins to drop at the rate of about 1/2” to 1” per minute. Before long the water level has dropped so much that the jets are exposed.
All equipment is Jandy. I’ve watched the plumbing equipment as the spa jets are turned on, and the valve actuator for the spa drain rotates a full 180°. That should turn off the spa drain and recirculate the water only in the spa. But, as I say, somehow the water level in the spa drops when the spa should be isolated and only recirculating.
This happens whether or not the spa heater is turned on.
I've tried to research this online, but it seems the most common problem is the spa water level dropping when the pump is turned off (usually indicating a faulty check valve). My problem is the opposite … water level dropping only when spa jets are turned on. No visible leaks in the pool plumbing—and any leak sufficient to drop the spa water level up to an inch per minute would certainly be visible. Also, when spa jets are turned off and pool returns to normal operation, the spa fills up again, and the pool water level doesn’t appear to have changed.
EDIT: After investigating further, the problem seems to be with a variable speed pump installed last year. To circulate the water better and make the water features more pleasing, we run the new pump at about twice the speed of the original pump. When I cut the pump back to the speed of the original pump, the water level in the spa remains constant when the jets are on. So apparently the new pump is pumping water out of the spa faster than it can be returned.
But that makes no sense to me. Where is the water going? Into the pool? I thought turning on the spa was supposed to isolate it from the pool. Any thoughts?
 
Last edited:
Rob,

When in the spa mode it is a closed loop, so that all the water that leaves the spa, must come back to the spa.

If the water in the spa goes down when in the Spa mode, the most likely problem is that your Return valve is not set correctly.

If that is not the case, then the jet pump is sending the water to more than just the jets or the jets line has a leak.

Thanks,

Jim R.
 
Rob,

When in the spa mode it is a closed loop, so that all the water that leaves the spa, must come back to the spa.

If the water in the spa goes down when in the Spa mode, the most likely problem is that your Return valve is not set correctly.

If that is not the case, then the jet pump is sending the water to more than just the jets or the jets line has a leak.

Thanks,

Jim R.
Jim, my edit and your post "crossed in the Mail". Looks like my hunch is consistent with your advice.
im not quite sure how to adjust the return valve. Any advice would be appreciated. Attached is a photo of the relevant plumbing (I think).
 

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Both ports that are connected to the pool must be completely off. For a spa to drain in use, the return valve is usually the culprit (all out of spa, some back to pool). If the valves show them as completely off, replace the diverters in the valves.

Conversely, if a spa continues to rise while in spa mode, it is usually the suction valve that is the issue (all into the spa, some still coming from the pool). It will also mean that is is nearly impossible to heat the water to temperature as cold water is continually being added to the spa.
 
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