Spa drains into pool with check valve flutter

[ddyszel320]

Hi, I bought a new home with pool 5 years ago and things worked fine...until February. That's when I noticed that my spa was slowly draining into the pool when the pump was off. I soon traced the problem to the Pentair spa return check valve where the flap seal had deteriorated. I replaced the flap assembly with a new one from Pentair, but the problem only slowed down. I noticed that when the pump was off and the return valve was split 50/50 between pool and spa, the flap would pulsate, making a clicking sound like an windup watch. Over night the spa level would go down about a foot. If I shut off the spa return using the 3 way next to the returns, the pulsing, clicking and draining stops. The pool store that sold me the replacement flap exchanged the the old one for a new flap. The visible oscillation seemed to stop, but the clicking continued, as did the draining. If I move the 3 way next to the return lines to shut off all the flow from the pump/filter assembly, I still have the same problem, but to a lesser extent.

Two pool service people have looked at it and are stumped although one suggested that the check valve was way to close to the 90 degree coupling setting of some sort of cavitation. The other suggested a stronger check valve. Since the system worked fine for 5 years until the flap seal failed, I can't understand why a plumbing configuration would suddenly cause a problem.

I did keep the pump off for a full day and the spa did drain down to the level of the returns. To me, it all points to the check valve, but I can't figure out why two model specific replacement parts, didn't fix the problem. Can someone please help?

 

[Jimrahbe]

320,

When the spa drains back into the pool, how low does the spa water drop?

In most cases the check valve is bad and replacing the "guts" fixes the problem..

In your case, my guess would be that the glub, glub action of the check valve indicates that you have an air leak somewhere.. Maybe right at the valve, but could be anywhere..

When you shut off your pump, does half the water in the pump basket drain back into your pool?

Thanks,

Jim R.

 

[ddyszel320]

Thanks for helping. The spa level can drop to the height of the return jets if I leave the pump off long enough....about 18 hours. The pump basket does not drain back into the pool. I have replaces the basket gasket, the gasket on the chlorinator as well as the gasket on the filter. We did check to see if there was air in the filter....there was none. The noise is much more like hard clicking. I have tightened all the unions. The original flap had an older foam type of seal that was soft and squishy. The two new ones use silicone. I have emailed Pentair to see if this change could cause the problem. Have not heard back. I did replace the gasket on the flapper valve assembly and made sure I had equal torque on all screws.

I'm going to close off the pool return line and then close off the intake at the pump tonight to see what happens. That should be a a straight short from pump intake through the filter and to the spa return with no way for the water to return to the pool.

 

[Jimrahbe]

320,

If the spa only drops to just below the spa jets, then the problem has to be in the check valve or the check valve plumbing..

You have an odd one for sure.. Please let us know if you find a fix, as it might help others.

Thanks,

Jim R.

 

[ddyszel320]

In an effort to remove as many variables as possible, last night after the pump turned off, I closed the valves from the main drain, the skimmer and the spa drain. I also closed the valve to the pool return. So, there was nothing coming into the system and the only open valve was the spa return. 13 hours later there was no change in the spa level and the check valve was closed and not moving. I then slowly opened the valve to the pool return and the check valve flap started visibly bouncing back and forth and the clicking noise returned. The is the situation I have when the spa drains back int the pool.

So with no pressure from input water or any of the mechanicals, what is causing this new check valve flap to open and start moving when the pool return is crack open?
Remember this system worked just fine for 6 years until the old flap in the check valve dissolved.

In the meantime I manually close the spa return every night and open it every morning.

 

[Jimrahbe]

320,

When you shut off all the valves, there is no place for the water to go.. So even if you had no check valve, the spa would not leak down.

Jim R.

 

[ddyszel320]

Correct. I wanted to make sure that there was no air leak problem in the system that would cause water to flow to the spa return with the pump off. If there is a proper vacuum, then the water from the very large and tall filter would not be able to flow out.

 

[ddyszel320]

I'm happy to say the situation is fixed. No one has been able to actually tell me why the problem happened but the solution was replacing the in-line Chlorine Feeder. The CMP Powerclean unit was immediately up stream of the Pentair check valve. While reading documents on the unit, I noticed that they casually mentioned that it has a built in check valve. I called the company and yes, it does and after some diagnosis, we determined that it wasn't working. For some reason the non-working feeder check valve set up an oscillation with the check valve on the spa line. Once I put in a replacement feeder (same brand on model) the situation resolved itself.

 

[Jimrahbe]

320,

I can tell you that I would have never thought of that as even a possibility...

Glad you were able to get it fixed...

Thanks for letting us know,

Jim R.

 

[xoringe]

FWIW, I had very similar symptoms as the OP. After 5 years, our elevated spa began draining down 4-5 inches/night while the pumps were off. Replacing the obviously degraded inline check valve flapper between spa return and pool return helped, but we still saw 2-3 inches of overnight drop. Also noticed visible (~2 mm) check valve flutter while pumps were off, accompanied by clock-like “ticking” noises from both the check valve and upstream Pentair 320 chlorinator (which also has its own ball-type check valve).

We re-opened the inline check valve and noticed that the seating surface was not uniform. (Top opening in attached photo.) At the lower edge, there was a ridge of pipe glue from the original installation. Our guess is that glue remolded the original flapper rubber to match such that they sealed for 5 years, but then the new flapper did not conform to the irregular surface. The small amount of leakage may have set up an oscillation that caused the flap to flutter closed/open.

We carefully sanded off the glue ridge, and that has fixed the flutter, ticking, and drain-down issues.

 

[slidingsky]

Thanks Xoringe. I was thinking a reverberating pulse between the spa check and the internal valves in the floor cleaner.
I got these generic replacement flapper for pentairs rubber junk and it was fluttering. Even an OE pentair kit did it. Im double checking the valve seats.

 

[slidingsky]

So my valve seat is good. The one at the floor cleaner for the spa flutters, but also my spa discharge flutter if left with the pool\spa diverter in halfway.
If i remove the floor cleaner valve mechanism lid, the flutter stops and the valves seats positively. It seems like some kind of water hammer pulse.
Ive seen weird stuff testing oil equipment on the bottom of the ocean, 9000ft of vertical pipe that shows massive pressure swings on surface despite pumps being off. Its like once a wave is bounced back and forth, it just keeps going, especially if it has a reserve of energy, a head difference.
I put the old valve back in that slightly leaks and no fluttering. Maybe spring tension or a weepy flap.
Anyone have an idea?