Air bubbles in system only when booster pump turns on

[allenV]

Hello,
I recently bought a home with a pool. It has a solar system which is great. Everything seems to be working fine and the pool water is at 80 degrees. Over the past few days something has changed.

With the main pump running, all is good, When the booster pump (PB4) tuns on to drive the pool cleaner air bubbles come out the return lines, a lot. The BP4 does not sound like it is getting fully primed.
When I shut down the booster pump the air bubbles are purged from the system and all is well again.

There are no leaks, I've opend and cleaned the U joints, inline filter basket (o-ring clean). Pressure at the filter is at 15psi and has been the same since I switched in the solar 2 moths ago. No air seen in any of the clear valves, that is until the Booster pump is turned on. lots of air bubbles seen in the clear fitting on the return line from the roof.

What could have gone wrong?
Any input is appreciated.
Allen

 

[mas985]

Welcome to the forum but you might have missed this: pool-school/read_before_you_post

Have you tried cleaning the filter and do you know the clean filter pressure?

Does the filter pressure change when the booster turns on?

Where is the booster suction line plumbed into the plumbing? A picture might help.

What is the panel height and where is the vacuum release valve?

 

[alanpaul]

Based on a friend's experience: It's possible the pump cover has a hairline crack, maybe even invisible. Try pouring a bucket of water over the cover, all the seals and all the pipe joints. Do the bubbles disappear at any time? For our friend, we replaced the cover, bubbles gone, and water moves more efficiently.

In our own particular case, a ball valve failed and was drawing air in around the cap. I took off the round cap cover, put a 2" square piece of heavy plastic bag over the handle, put the cap back on to hold the plastic in place. Will replace the valve in the future, but for now, no air intrusion, no bubbles.

Welcome, and Good luck.

 

[allenV]

Thanks for the responses.
I tried the water on the pump with no change to the air in the line.
Questions:
Have you tried cleaning the filter and do you know the clean filter pressure? (10psi w/o solar; 15psi with solar
- Yes, as soon as I took over maintenece of the pool. have not cleaned since - 2 months
Does the filter pressure change when the booster turns on?
- No it does not change. 15psi steady. Before I switched the solar panels in it was 10psi.

Where is the booster suction line plumbed into the plumbing? A picture might help.
- Plumbed into the return line to the pool - after solar. (haven't figured out how to include image yet)

What is the panel height and where is the vacuum release valve?
- I am not sure - on roof of two story house. The only pressure release I know of is on top of filter.

I am new to this so I am sorry that I don't know if there are valves on the roof as part of the solar panels that can leak air.

One more observation is that it takes a good 15 seconds after the booster pump is turned on before air bubbles are seen.
Once the booster is turned off it takes 20 seconds to purge the air from the system.

Allen

 

[mas985]

More than likely the booster is increasing the suction (by reducing return head loss) and the pump basket is leaking. Check the pump basket with the booster on vs off. Do you see bubbles with it on?

 

[JamesW]

The booster pump might be pulling enough water from the returns to open the vacuum breaker valve at the top of the solar panels. It might be very close to opening without the booster, and when the booster comes on, the breaker opens. You might be able to increase return head by adding eyeball fittings to the returns or using smaller eyeball fittings.

 

[allenV]

Mark,
I checked the basket at the main pump, before the filter, no air in that part of the system, no air leeks, booster on or off.
The air bubbles can be clearly seen in the 'clear' check valve on the return line from the roof, when booster pump is on, clears when turned off.

James,
the system has been fine since end of Feb, just started happening a few days ago.
Is this a failure mode of the vacuum breaker valve?
Replacing this valve might be the fix as opposed to swapping out eyeball fittings (whatever they are )

thanks for your comments.
Allen

 

[mas985]

I missed the part about the booster being plumbed in after solar. It might be better if it was plumbed before solar.

But if the filter pressure is not changing when the booster goes on, then the pressure at the VRV should not be changing either. 15 PSI at the filter with the booster on should be enough for a two story VRV installation with some margin. Flow rates for boosters are pretty low so the pressure change should not be much. It could be it is right on the edge which might explain why it didn't occur before. I would clean the filter and see if the problem goes away. If so, you might consider plumbing the booster pre-solar instead of post solar or cleaning your filter more often.

 

[allenV]

Thanks again for the ideas and suggestions.

I cleaned the filter cartriges this morning, I was suprised how dirty they had gotten.
Filter pressure after cleaning, 14.5psi.

Same air in the pool return lines when booster is turned on.

Perhaps it's time to upgrade to a Polaris 360 model which can operate at only 15 - 17 PSI, no booster pump required. :-(
(or get someone out here who understands pressure side cleaners
Allen