Spa drains to pool - help...

[dphanes]

We have a pool and spa combo where the spa level is higher than the pool. The pump equipment is slightly below the level of the spa/pool

Whenever we go from spa mode to pool mode or pool mode to spa mode, the level in the spa goes down by 1/4 inch. The level is stable as long as we don’t switch modes. As you can see in the picture below, we don’t have a check valve between the pool and the spa and my guess is the spa is draining back into the main pool as it is higher elevation and there is no check valve.

Couple questions -

does this seem to make sense as the cause?
any other thoughts on what it could be?
am thinking about adding a check valve (see drawing below) to stop the flow from spa to pool. Given the configuration we have to add a couple 90 degree elbows and am wondering if that will hurt overall efficiency or whether anybody can think of another solution.

any help would be great appreciated!!!

 

[ajw22]

I don't see the level of the spa going down by 1/4 inch a problem when going into spa mode. The spa water level needs to drop a bit below the spillover. When people get into the spa they displace and raise the water level. In my spa water often gets lost over the spillover as people get in and thew ater level gets a bit lower.

What problem does the 1/4" cause?

 

[mas985]

does this seem to make sense as the cause?

Yes, however, even with check valves, the spa will always lose some water while the valves are traveling from one setting to another. There is no way to prevent that. Usually, it is not that big a deal since once you get in the spa, the water will overflow anyway. BTW, is the pump running when the valves are transitioning? In most controllers, you can set them up so the pump shuts off during the valve transition which minimizes both water hammer and water level changes like you are describing.

am thinking about adding a check valve (see drawing below) to stop the flow from spa to pool. Given the configuration we have to add a couple 90 degree elbows and am wondering if that will hurt overall efficiency or whether anybody can think of another solution.

Check valves would only help when the valves are in spillover mode (pool suction, spa return) and the pump shuts off. The water will drain from the spa to the pool until the levels are equalized without the check valves. But again, check valves will not help much during the valve transitions from pool mode to spa mode.

There are several paths where the spa drains. Spa return -> pool return, spa return -> pool suction, spa suction -> pool suction, spa suction -> pool return. The check valve will only take care of the spa return back flow and/or the pool suction back flow. You can't do anything about spa suction -> pool return during valve transition.

If you do put in a check valve, it might be better to put in on the spa return side to minimize head loss on the suction side of the pump as well as major plumbing changes. This will prevent flow from the spa return out the pool suction when in spillover mode with the pump off.

 

[dphanes]

Appreciate the replies.

Normally it wouldn’t matter, but our auto freeze protection rotates between pool mode and spa mode every 30 mins so over the course of the night the 1/4 inch drops add up to a 4 inch drop over 8 nighttime hours which exposes the plaster.

I definitely wasn’t thinking about the return causing the drop as well.

 

[ajw22]

Time to ask you to create your signature with details of your pool and equipment so we know what controller and stuff you have.

 

[mas985]

Appreciate the replies.

Normally it wouldn’t matter, but our auto freeze protection rotates between pool mode and spa mode every 30 mins so over the course of the night the 1/4 inch drops add up to a 4 inch drop over 8 nighttime hours which exposes the plaster.

I definitely wasn’t thinking about the return causing the drop as well.

It is unlikely that check valves are going to solve that problem. Are you sure you need freeze protection?

The Physics of Freezing and Freeze Protection

Recently, there have been a lot of questions from those living in moderate climates about using automatic freeze protection or running pumps to prevent freezing and what a pool owner should do when temperatures drop so I thought it might be useful to have a thread which dealt with the issue from...

www.troublefreepool.com

Just because air temps get below 32F, does not mean there is a danger of freeze damage.