Return line bubbles only when solar system is on

Titanium · Sep 4, 2007

Hello,

I have had a large increase in the rate of bubbles in my first pool return in the last couple of days. I normally have a small amount of very tiny bubbles in this return line - i.e. a very tolerable amount. But in the last two days, a massive amount of b bubbles has started coming out, but only when the solar diverter valve is sending water up to the second story solar panels. Even though the amount of bubbles is very large, it is not enough, apparently, to cause the 2 HP filter pump to lose prime.

It is apparent that I have developed a large air leak somewhere in the solar panel water piping, but I was under the impression that air leaks only occured in the suction side of the filter pump, and that any leaks downstream of the filter pump would manifest themselves as water leaks. And I thought everything in the solar panel water piping would be under pressure - not vacuum - since it is all downstream of the filter pump.

Any ideas? Thanks!

Titanium

duraleigh · Sep 4, 2007

That's interesting. Mas985 is the "go to" guy on this stuff but I'll dream up an opinion, anyway.

First of all, your thinking about pressure side leaks is correct. Perhaps an exception could occur when the water is moving downward off the roof. The force of gravity is in effect and I wonder if it may be strong enough to, in effect, "depressurize" the downward portion of that piping, thereby creating a negative pressure differential which would then perform exactly as a suction-side leak.

I have no idea if that idea will stand much scrutiny but thought I'd throw it out.

If, by luck, that's correct I'll edit this post to make it seem like I knew what I was talking about all along. :roll:

mas985 · Sep 4, 2007

Titanium,

I assume that you are not talking about the air that normally comes out of returns when the solar is turned on during the panel priming process. After a few minutes all of the air should be purged and you should no longer see any bubbles.

You are correct in that both the upward pipe and downward pipe for the solar are both under pressure but different amounts so no air should be able to enter. Any leaks will show with water coming out and not air going in.

The only exception to the above is if the panels are not priming properly and the vacuum release valve is not shutting. Under this scenario, the pressure will not build enough and could possible carry air with it. However, your pump is large enough that there should be no problem priming the panels.

What does your pressure guage read?

Also, do the bubbles ever go away and if so how long does it take?

Titanium · Sep 5, 2007

mas985,

Once the solar valve is in solar mode, I get the normal solar panel bubbles for a minute or so until the solar panel purges all of the air. The air bubbles I am seeing now are brand new and quite different from the normal solar panel "belching" that happens at the pool returns.

My cartridge filter is very dirty and needs cleaning, so my pressure gauge is now reading 32 psi.

No, the bubbles will go for 20, 30, 40 minutes, or until I can't stand looking at them any longer and turn off the solar diverter valve.

I think I am just up the road from in SR.

Titaniium

mas985 · Sep 5, 2007

A dirty filter could cause some problems with complete priming of the panels. If the pressure loss in the filter is too high, there is not enough pressure in the panel to completely close off the vacuum release valve and it could draw in a small amount of air depending on the pressure differential.

I would try cleaning the filter to see if that helps. That is about the only thing I can think of that would cause air to get into the return system.

tphaggerty · Sep 5, 2007

Another possibly is that your vacuum breaker valve has gone bad. This is the valve that opens up when your pump stops and lets the water drain out of the solar system back into the pool (you must have one of these, otherwise you wouldn't get lots of air when your system first starts up). These valves can go bad, they get corroded, etc. You normally will have one of these.

If you hear any sucking like sound near the panels when they are running, this is probably what is happening. When I had my panels installed, the first valve was bad and the 2nd (which was good) had to be positioned lower on the panel plumbing. In both cases, I was getting excessive air into the system. Your panels should be AFTER the filter, so the bubbles won't cause any problems with air in the filter, they are just annoying and do reduce the efficiency of the system.

bluenoise · Sep 6, 2007

mas985 said:
A dirty filter could cause some problems with complete priming of the panels. If the pressure loss in the filter is too high, there is not enough pressure in the panel to completely close off the vacuum release valve and it could draw in a small amount of air depending on the pressure differential.

I would try cleaning the filter to see if that helps. That is about the only thing I can think of that would cause air to get into the return system.

This is exactly what happens on my system. When the cartridge filter's pressure is too high when it needs cleaning, the relief valve near the panels starts sucking some air and I get bubbles in the returns. I also hear it "snorting" like a pig up there.

Titanium · Sep 8, 2007

mas985 and bluenoise win the troubleshooting award. :party:

Honorable mention goes to tphaggerty and duraleigh. :cheers:

After I cleaned my nasty dirty cartridge filter (all four of them

), my problem with bubbles coming out the return line while the solar panels are in operation has went away.

Observations:

1. Holy cow, I have never seen my pressure gauge read so low (I changed my original Hayward filter pressure gauge out a month or two ago, but had not cleaned the fillter since the gauge changeout). My pressure gauge now reads 21 psi. :-D :-D

2. Pressure gauge readings

Before filter cleaning............After filter cleaning.............After filter cleaning
........................................................(w/ PoolSkim)..................(w/o PoolSkim)

30 psi......................................................21 psi......................................19 psi................................Normal Mode

32 psi.......................................................26.5 psi..................................26 psi.................................Solar Mode

3. I had never noticed before, but it probably took a good 10-20 minutes, while in the solar mode, for the bubbles to stop coming out of the return. In other words, it takes a fair amount of time for my solar panels to completely purge themselves of air.

4. The PoolSkim in-pool skimmer really loves the additional pressure available to it now that the filter is nice and clean. The PoolSkim makes an even bigger vortex inside the "floating hat" than it did before. In fact, the PoolSkim is even sucking air from the surface of the pool and expelling the air out into the bag. This was very misleading at first in that I thought the air was coming from an air leak. The PoolSkim DID NOT entrap air in its vortex before the filter was cleaned.

5. The PoolSkim, surprisingly, causes a 2 psi drop as compared to having a wide open return (without even an eyeball, just a bare open 1.5 inch pipe).

6. With a clean filter, the psi change from Normal Mode to Solar Mode is 5.5 psi. With a dirty filter, the psi change from Normal Mode to Solar Mode was only 2 psi. My hypothesis to explain this observation is that the piping losses must have been greatly reduced because the flow rate from the filter pump was significantly reduced due to the higher pressure drop across the dirty filter.

7. I think the filter pump is louder now as compared to before the filter was cleaned. Again, I think the filter pump is now pushing a lot more gallons per hour (increased flow rate), and this increased flow rate through the piping and equipment is causing a higher noise level.

Titanium