Air in return outlet

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Henry M

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Oct 7, 2015
230
Coral Springs, Florida
Have noticed that when I close the main drain, so only skimmer is sending water to pump, there is a constant presence of tiny air bubbles coming from the return that is at the deep end, nearest the pump/filter. When the skimmer is closed and only the main drain is sending water to pump, there are no air bubbles. I've a SWG, but these are not the same bubbles as produced by it. I replaced all the O rings on filter, etc. No visible signs of leaks; no water on cement pad that pump & filter sit on; no moisture on SWG or any other connections. I'm at complete loss. Anyone have any ideas?
 
This is common, especially with a circular style skimmer weir. Small amounts of air bubbles from aggitation from the weir are pulled through the plumbing and make there way to the pump basket.

Check to make sure that the water level is at least at the midpoint of the skimmer mouth and that the door or circular wier is operating correctly.
 
Since your issue seems to be isolated to the skimmer line, I would still pursue all fitting/joints on the outside with another test for (air) leaks. Try the hose/water test slowly over each joint, valve, fitting, anything that could allow air to get sucked-in. While the system is running, it's pulling-in air, so you won't necessarily see a water leak, even when turned-off. The water test is the most popular, but others have tried smoke or shaving cream - each with it's own challenges and success rate. Of course if the weir is operating correctly, water level good in the skimmer, and all above-ground items checked for air leak, your issue may originate under the skimmer or within a pipe underground. Even more reason to be very slow and deliberate when checking everything from above.
 
A weir door/flap is ideal to help "groom" water flow from the nearby water surface towards the skimmer, while also preventing debris from leaving the skimmer when the pump is turned-off. The fact you have no weir door at the moment should not be a factor in the creation of air bubbles as long as the overall pool's water level is sufficient - about halfway up the skimmer opening. If the water is too low it can suck-in air.
 
You have a circular weir as I mentioned before. They are much more prone to causing a vortex that lets small amounts of air into the pump basket. It isn't a problem unless your pump is losing its prime or cavitating, both of which I'm doubtful is happening.
 

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Thank you Texas Splash. What sort of compound should I put at each joint, valve, fitting etc if I find that it is allowing air to enter? If I decide to just put some sort of compound over all those areas as a preventative measure, should I use the same compound, or another? Thanks very much.
 
In general, you really shouldn't have to put any sealant around all the pipe joints/connections. They should be sealed well from the original PVC primer/cement. But if during the course of your inspections you find that you have a tiny, specific spot on the suction side, on a pipe that is exposed, allowing air to get pulled-in, you might try an exterior grade caulking if it's a very small spot. It may help to close the gap. If that doesn't work, perhaps a stronger epoxy. There's a variety of such items that should work. But if the leak is too big and the suction in that spot is too great, you might just have to eventually cut and replace that fitting or section of pipe. If that doesn't help, or you need more ideas, check back with us.
 
Air bubbles are back, this time whether suction is from main drain or skimmer. Water level in pool is half way above the skimmer. No vortex in skimmer. I see tiny bubbles when looking through the clear lid into the strainer basket. When I open & close the pressure relief valve on top the filter, air escapes for a nano-second then water in a steady stream. I've put caulking around joints & connections. All O rings were replaced about 3 months ago. Am unsure of next steps. Anyone have any ideas? Thanks very much.
 
Aside from anything underground Henry, I'm about out of ideas myself. I know VSPs can have a small impact on generating tiny bubbles at times, but those are usually flushed-out at a higher RPM once a day or so. Your situation sounds much like mine. I have a 2-speed on low almost all the time and it does the exact same thing. I'm to the point where the OCD in me has just about given up ... but then I let it get to me sometimes. :brickwall: You might get to a point where as long as it's not effecting overall prime or significant water loss in the pump strainer basket, that you just accept it .... as long as nothing gets worse of course. Wish I had more to contribute for you Henry.
 
Texas Splash: your comments are exactly what is beginning to circulate through my head. I just realized my own version of OCD is letting this get to me. Enough. The water level in the pool has stayed constant; pump has not lost is prime; & very little water loss in the strainer basket. Please know that your comments have been more than helpful & very much appreciated. I'll do my best to just accept that this is just some strange sort of anomaly for which there seems to be no explanation. Again, many thanks.
 
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