Leak suspected in built in hottub

[Zalick]

I have a 13000g plaster pool with a connected 800g hottub. The hottub is above the pool with a waterfall.

I’ve noticed the hottub water level dropping more than seams reasonable due to evaporation. The tub has a cover, but it’s not totally covered due to the waterfall part. The cover has a flap for the waterfall but there is some evaporation that will occur around the flap. Maybe 1/2” gap around the flap.

I think I’m loosing around 10-15g a day. I’m going to mark it today to get a better 24hr measurement.

I think The plumbing for the tub goes under the pool.

The tub is at 80-100 depending on time of day. Ambient temp has been around 50-60.

Is it possible for 10-15g to evaporate out just around the edges of the flap?

If it’s a leak in the pipes, is there a way to diagnose and repair without tearing everything up? The cost to tear it up will greatly outweigh the cost of the lost water.

I have not seen any obvious water downhill of the pool. Everything is deep enough that I don’t think I would be able to see 10g dispersed over 24hrs.

 

[tstex]

Fill spa to the very top at 6pm your time. turn off all pumps and close the top completely. See if you have any loss overnight? Many times this issue is due to a leaklng ck-valve. If no water loss, then it's not the ck-valve.

Now, a little thermodynamics. If your evening temps drop to 50 and your water temps are 80-100F, then you could be losing water due to the water steaming out of the spa. Turn the spa temp to the ambient temp and if this is the issue, this will resolve it bc you're in equilibrium.

Do some overnight testing and post back. One last question. Has this ever happened before? If so, what time of yr and the conditions?

Best, tstex

 

[Zalick]

Fill spa to the very top at 6pm your time. turn off all pumps and close the top completely. See if you have any loss overnight? Many times this issue is due to a leaklng ck-valve. If no water loss, then it's not the ck-valve.

Now, a little thermodynamics. If you evening temps drop to 50 and your water temps are 80-100F, then you could be losing water due to the water steaming out of the spa. Turn the spa temp to the ambient temp and of this is the issue, this will resolve it bc you're in equilibrium.

Do some overnight testing and post back. One last question. Has this ever happened before? If so, what time of yr and the conditions?

Best, tstex

Thanks! Great suggestion on letting it get to ambient.

I have only lived here for 7 months. I did not notice anything unusual until this last week when I was out of town. Came back and it was 6-8” below the top. My wife and kids didn’t use it while I was away.

Previously I used it regularly and with the waterfall, so I never noticed a dramatic drop.

I will try your suggestions and report back!

 

[Zalick]

Fill spa to the very top at 6pm your time. turn off all pumps and close the top completely. See if you have any loss overnight? Many times this issue is due to a leaklng ck-valve. If no water loss, then it's not the ck-valve.

Now, a little thermodynamics. If your evening temps drop to 50 and your water temps are 80-100F, then you could be losing water due to the water steaming out of the spa. Turn the spa temp to the ambient temp and if this is the issue, this will resolve it bc you're in equilibrium.

Do some overnight testing and post back. One last question. Has this ever happened before? If so, what time of yr and the conditions?

Best, tstex

Turned off spa heater. After 36hrs with top on, I lost about 8 gallons. The spa temp is still 80 degrees and ambient temp in the 50s. I do see steam coming off the top of the cover (it’s raining). I suppose it’s possible 8 gallons is evaporating out of the small gap for the waterfall?

 

[tstex]

what are your daily winds there?

Let it get to equilibrium in temps, fill to top, and then note water level

How did you calculate 8 gals?

If you fill to top, all is covered, in equilibrium, then it’s probably your Ck valve

 

[Zalick]

what are your daily winds there?

Let it get to equilibrium in temps, fill to top, and then note water level

How did you calculate 8 gals?

If you fill to top, all is covered, in equilibrium, then it’s probably your Ck valve

I calculated based on it dropping about 1cm over that time. It’s 6’ x 6’.

Ok, I’ll try letting it get to full equilibrium. Our winds have been 5-10mph intermittently the last few days.

Could the Ck valve be slowly leaking in to the main pool system, so the pool is slightly increasing on water volume but due to size it’s not noticeable? Then with frequent use of the waterfall, the levels balance again before the pool would start to overflow?

 

[tstex]

Yes, water from spa (if higher than pool) will move from spa to pool w bad Ck valve. And, if it’s a waterfall from spa to pool, when main pump comes on will refill spa and even water levels.