No pressure when using bottom main drain...

[pdifranc]

Hello all. i'm having a heck of time. i'm trying to help my sister who has an anthony/sylvan plaster pool, with 2 skimmers, 3 returns, and 2 main bottom drains.. the problem is that when the main drain valve is working, there is NO pressure coming back through the system, but when i turn the valves to only work via the skimmers, pressure is FINE. The problems only seem to arise when i have isolated the main drains at the bottom of the deep end.

Questions - 1: there are 2 main bottom valves in the deep end? Is one a return and other inlet valve? 2: can they be clogged with hair and such? i cannot see any leaves or visible materials. 3: can i actually go down in the deep end and service these main valves with the water in the pool?

I am pretty well versed as i have my own inground pool, however i do not have main bottom drains, i have a side-wall set up.

any advice is appreciated!!

 

[duraleigh]

Hey,

Welcome to the forum. :lol: It sure sounds like the main drain line is blocked. When you say you have no pressure I assume you mean the psi guage is at or near zero and the flow back into the pool is at or near zero as well, is that correct?

 

[pdifranc]

Thanks duraleigh.. by no pressure, i mean very light water force (very little) out of the return inlets by holding my hand in front, pressure seems to be stable between 18-22... and then the skimmers barely show any activity...

 

[duraleigh]

Well, since you're not getting normal flow when your source is main drain only, then it certainly seems the main drain (or the line) is restricted. I am a little surprised the psi doesn't drop when you select the main drain as the source...it should (drop).

The two fixtures at the bottom are both drains and the obstruction is likely (but not definitively) down there. To do any meaningful work, you will probably have to enlist someone with SCUBA experience to remove the covers and examine them for any blockages.

The only other possibility I see is you may be overlooking a partially closed valve, but that doesn't make much sense given your familiarity with pools.

It is not overly unusual for some people to intnetionally block the main drain for one reason or another. Is your sister the first owner of the pool?

 

[pdifranc]

Great point of the valve, maybe the vale is not working right. I'll double check tonight. Also, fyi, I spoke to a friend and he said there could be some air pockets causing this potentially. I'm going to do both, and have a friend who is scuba cert. Look at it on monday.thanks so far!

 

[duraleigh]

and he said there could be some air pockets

You're not losing prime (air in the pump strainer basket) when you switch to main drain as the source, are you?