how to find blockage in recirculation loop

[semenzato]

Greetings,

I am experiencing intermittent blockage of the PVC pipes between
the filter and the pool. The pressure gauge at the filter shows higher
than normal pressure, and there is very little flow. If I turn off
and on the pump several times, the blockage goes away.

The question is, how do I find where it is? I have examined
the filter and nothing seems wrong with it. After the filter
there is a check valve (one-way valve) and I strongly suspect
that's the culprit. Then there is a three-way valve to optionally
direct the flow through the solar panels. Then there is a manual
valve, and then the Pool Pilot chlorine generator.

Pressure gauges on the web are cheap ($5 to $10).
I don't mind buying two or three and leaving them
permanently installed in order to isolate this one problem.
But they have copper male threads and I don't know
if there is any simple way of installing them on 1.5"
PVC pipes. Any suggestions?

Thanks!
Luigi Semenzato

[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