return line issues

[plcguru]

Hi,

I have an IG true-L shape pool with vinyl liner. It has a return line for the steps with 2 jets. They both shoot out at 'normal pressure. Never problems.
The other return line has 3 jets, 2 in the shallow end, 1 in the deep end. The 2 in the shallow end shoot out at 'normal pressure' but he deep end one does not.

When the pump first starts, all 3 jets have normal pressure. When the deep end loses most of its pressure (maybe 1/2 hr later????) I can cover it with my palm and feel pressure building, air bubbles will eventually come out the low end jet closest to it in the shallow end. Then I remove my palm and all 3 jets have normal pressure again.... then the problem reappears in about 30 minutes.

Pressure at the filter is 18psi which it has been for years before the problem appeared(it appeared thsi year only)

Any ideas about troubleshooting?

If it helps, the problem jet is closest to the pump/filter. If I move the valve on my plumbing to turn off the return line for the jets at the steps I have real high pressure on the return line with the 3 jets and no problems.

Thanks!!!!!!!!!

[Searcher]

Hi,

Pressure at the filter is 18psi which it has been for years before the problem appeared(it appeared thsi year only)

Any ideas about troubleshooting?

If it helps, the problem jet is closest to the pump/filter. If I move the valve on my plumbing to turn off the return line for the jets at the steps I have real high pressure on the return line with the 3 jets and no problems.

Thanks!!!!!!!!!

It sounds to me that you have a small suction side leak, hopefully just from the pot lid. This would be where the air is coming from, and just fixing that "may" cure the issue.

We really need to differentiate between pressure and flow and please don't think I am ragging on you for semantics.

Without getting into a huge explanation between the two; the bottom line is your pump may be moving less water than when it was new which equals "flow" while is will still maintain the "pressure" you see at your gauge which comes from a combination of filter media restriction, friction loss due to the length of your pipe runs and the amount of 90 degree elbows that were used on your pool where 1 ell equals about 10' of pipe.

In short, you may have had this "problem" since the pool was new and it is now manifesting itself as the pump has aged and lost some of its flow or because of the suction side leak.

With what you said re the trouble return being closest to the pump; water will flow in the path of least resistance so my thoughts are that this one return may well have 4 to 6 ells installed OR it may be lower that all of the other returns but the tee, or wye that was used is facing upwards which would create a reverse trap like you see under your kitchen sink. This trap is filling with air causing the loss in flow which explains the half hour for the problem to manifest itself. A wye in the line, placed backwards and upright would make the matter much worse.

When you place your hand over that return you cause a venturi effect that actually sucks the air out of the locked line where the air shows at the other returns and then, WHAM you again have flow through that mystery return.

This all presumes that you have no abnormal water loss from leaks which you did not mention as a possible problem.

So what to do?

Find the suction side leak and/or crack your steps valve closed a bit to send more flow through the mystery return, Considering the issue, a replacement pump, at this time is silly but this depends on the age of the equipment of course.

As an after thought, 18 pounds pressure is a lot in my eyes when you consider that I run a 25K gallon pool with two inlets and two returns, with a 1 horse/1 sixth horse motor with 3 pounds of pressure before a 24 inch sand filter.

[Poconos]

An interesting idea with the trapped air in the pipe. Let's start with the pump and filter. Makes and Models? Bubbles are a clear sign of an air leak but when the system reaches steady state, the condition after 30 minutes or so with the reduced flow in the one return, you should see bubbles out the normally functioning jets and see them in the pump basket. It can't be a big leak or the pressure would drop. The 18 psi does seem a little high for a clean filter assuming sand. If it is trapped air in that one pipe, covering the other two jets should blow it out and that should be clearly visible as the air is purged. For another piece of info you may try removing the eyeballs just to see what happens. Those things present quite a restriction and I bored mine out some to increase flow.

The buggy part of this problem is something appears to have changed. Plumbing usually doesn't change so that leaves the filter and pump. Consider the pump. Check the impeller to make sure nothing is tangled in there. Been many instances where people find stringy things that got past the skimmer and pump baskets. Otherwise nothing should change unless the pump overheated somehow and was deformed, but unlikely since the pressure is 'normal'. So let's consider the filter. Need to know more as I asked above.

Al

[Searcher]

The buggy part of this problem is something appears to have changed. Plumbing usually doesn't change so that leaves the filter and pump. Consider the pump. Check the impeller to make sure nothing is tangled in there. Been many instances where people find stringy things that got past the skimmer and pump baskets. Otherwise nothing should change unless the pump overheated somehow and was deformed, but unlikely since the pressure is 'normal'. So let's consider the filter. Need to know more as I asked above.

Al

Al, as an after thought, I would venture to guess that his filter may be marginal for the pump that is in place. Since a too big filter is excellent compared to a too big pump that causes horrors; that may be yet another issue.

I wish the OP would have posted pool size in gallons, pump size, pipe run lengths etc. It sure helps to diagnose stuff like this.

As for an air lock, you should see it on a hydronic heating system that is not piped properly, but with that and most pipes exposed, it is easy to diagnose.