how to find blockage in recirculation loop

[duraleigh]

If your pressure guage reads higher during the blockage, the problem is somewhere between the pressure side of the pump and the return eyeballs.

[cleancloths]

I would be willing to bet the check valve is the culprit. It is quite hard to get a blockage in PVC pipe - what do you suspect this blockage might be?

[mas985]

During one of the high pressure moments, leave the pump on and tap lightly with a hammer on the check valve and see if it lets loose. If it is stuck it should swing open and the pressure drop.

[semenzato]

Thank you for the advice. I just tried tapping the valve but it didn't have any
effect. I still suspect the valve, though.

I tapped reasonably hard but I had to make an educated guess as to how hard
to avoid cracking the valve casing.

Oh well, I guess I'll replace the valve and pray that's the problem.
I will post on this thread as soon as I do it.

Thanks!
Luigi

30'x16' (irregular) indoor gunite/plaster pool, about 10k gal
Pool Pilot SWCG, 3/4 HP recirc pump, solar panels, heat
exchanger from 200 BTU/hour Viesmann boiler

[Poconos]

Whacking PVC with a piece of 2x4, not pressure treated, is pretty safe. Pressure treated seems a little harder, but still softer than a hammer. Or, use a piece of PVC pipe.
Al

[semenzato]

Whacking PVC with a piece of 2x4, not pressure treated, is pretty safe. Pressure treated seems a little harder, but still softer than a hammer. Or, use a piece of PVC pipe.
Al

Thanks, I appreciate the PVC-whacking advice.
I am quickly becoming an expert on whacking PVC.

I found drawings on the Web on how this particular check valve
is built. There is just a little door. I am guessing that the door
doesn't stick completely closed, because there is a tiny bit of flow,
which varies from run to run. So it may be the hinge. In this
case it's not clear that further whacking will reveal anything,
because the door may be required to jiggle a bit to become loose
(instead of just unsticking from the opening) and the whacking
is not necessarily going to be effective.

I found a place that sells *transparent* PVC check valves.
I am getting one of those so next time I'll know for sure.

Luigi

[duraleigh]

Hi, Luigi,

I have never been a fan of check valves......because of the problems they cause.

Would your system function without one?