Bubbles from the return lines

drewmanOctober 22, 2007

My pool is finished and it is nearly perfect. But I have noticed that there are bubbles coming from the returns. Also, every morning that it starts it blows air from the lines for about 4 minutes causing a boiling effect due to the large volume of air in the system. My observation is this. It appears the bubbles are coming from the suction side line and not any seals or fittings on the pump. The return will shoot out bubbles off and on intermitantly as the pump runs. I am sure this is due to air building up in the filter and then being expelled. My pool builder is trying to convice me that there is no way that there is a suction side leak and that the bubbles are being caused by cavition. The suction side line is about 100 feet long. I have a 4x160 pump that runs at 1000rpm on the daily cycle speed. The plumber came over today and tried to talk me out of doing a suction side pressure test insisting that it was a waste of time. but I insisted. He will pressurize the suction side of the system on thurs. Am I being unreasable by insisting that there must be leak? Does anyones pool blast air out of the return after the system cycles on? Does anyone give any credibility to the cavitation idea? I would appreciate any guidance on this issue.

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I wouldn't say you have a leak.
With a little investigation you'll probably find that it's water from the filter amd the pump seeking its level with the pool due to a bad seal somewhere.
It could be one of the male adapters or one of the o-rings on the pump strainer lid, between the halves of the filter, under the pressure gauge, or even the Jandy valves. If you started up your daily cycle on a regular speed these bubbles would be gone very quickly after start-up because you'd achieve a quick prime. I'm not certain but I believe that the 4x160 starts up and runs on the designated RPM's.
I've also seen where it was a stuck skimmer weir door that wouldn't come down all the way due to a little friction where it glides down the sides of the skimmer throat, once the pump pulled strong enough prime the door would stay down and not allow any more air to enter the system.
If I was told about these symptoms I'd check these items before I broke out all my gear to perform a pressure test.
I'm curious, when you say the suction side line is 100' long, do you mean that there's only one pipe servicing all the suction of the pool, if so what's the diameter of the pipe?

See ya

    Bookmark   October 23, 2007 at 1:23AM
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I believe (I am not home right now) that the suction line is 2 1/2 in to the pump. I have two skimmers and two bottom drains. Also I have had the seals checked and lubricated. The skimmers are not drawing any air and the door are free and moving.


    Bookmark   October 23, 2007 at 1:13PM
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Cavitation is not normal in most cases. It is a sign of undersized pipe and oversized pump. If you have what you say, it would not be cavitation.

Check the installation. Do you have a length of pipe going into the pump at least 8"? If it 90's right into the pump or only has an inch or two, that water velocity is most likely introducing air into the pump due to poor hydraulics.

Air purge on start-up is quite normal but should quit. On lower rpm's, it does take awhile. The only place air will be introduced into a pump is on the suction side. Crank that pump up to the highest set rpm and then turn it off while looking at the pipe going into the pump and the pump lid o-ring. Any ejection of water will indicate your source of air intake.

If you see none, and you have a diverter valve in front of the pump it could be leaking in the stem or cap. If you have a motorized valve, you will need to remove the 4 screws on it, and then the motor to do this test. If not, pull the handle off the valve and repeat the pump going off test but this time, look at the valve for water ejection.

If these all check out ok, assume the request for a leak test is valid if you purge all air from the filter and the returns continue to bubble.

    Bookmark   October 23, 2007 at 8:02PM
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I correct myself. The Suction side has a 2" line, not 2 1/2 that services the entire suction side. The plumber pressurized the suction side yesterday and it appears there are no leaks. From your comments I suspect that the suction line is undersized for the length of run.

    Bookmark   October 26, 2007 at 11:09AM
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Drewman take a water hose and with a low stream of water go over all your fittings in front of the pump and see if the air stops at any given fitting.

    Bookmark   October 27, 2007 at 7:27AM
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so i'm following this same path here. i was wondering if the diverter/3 way valve is servicable if it happens to be the culprit. whether it be a stem leak or a body gasket leak.

for future reference, i'll post some details, cause it sounds like i'm gonna be chasing this for a while.

the suction from the spa and pool are 2.5", the suction from the cleaner is 1.5". for some reason there is a 2" piece between the spa valve and the pump... the pump is a 2 speed 2hp.

what i'm seeing is small bubbles comming out of the returns at low speed in the pool. at high speed , i dont' see them at the pool, but i see them like crazy in the pump bucket.

i've ruled out the pump seals and spa, as when i switch the valve from pool to spa, the pump bucket clears instantly and is 100% full of water.

at low speed, the small bubbles come out of the pool returns whether it's on cleaner or skimmer/floor... kinda leads me to believe it's in the cleaner valve.

i did accidentally turn the cleaner on breifly (10 secs) on high and the bubbles in the pump went crazy and i got massive cavitation, but i'm guessing that was because of the small diameter pipe...

anyway, i think it may be getting worse as the last couple days, when i come home, the pump basket is only 25% full. it was only last week the bucket was always full and i had never seen bubbles in either the returns or the filter bucket...

so for now... does it at least sound like i'm looking in the right place?

    Bookmark   March 21, 2008 at 9:32PM
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btw, the pool is all of about 2 months old...

let me know if this would be better posted in it's won thread. i figured it'd be better here as future searchers might find info all in one place.


    Bookmark   March 21, 2008 at 9:37PM
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The picture is not too clear but you seem to have a real funky connection between the two valves. What is it?

Yes, the valves can be serviced and yes they do leak. At a couple of months, not really unless the pump ran dry.

You can remove the motorized valve (4 screws)and then turn on the pump. Turn it off while watching the valve stem. If you see a small drip of water or hear air, you have a leak there. Do the same with the sweep valve.

There are two o-rings on the valve diverter and one cap o-ring. If the cap o-ring fits loosely, the pump ran dry and the valve got hot and shrunk. This will cause the air leak. At that point you need a cap also. If the cap o-ring fits snug, you can try new stem o-rings.

When you do the test by turning the pump off, also look for water squirting out of the fitting screwed into the pump. Is that a Tri-Star pump. It may be oversized as most of them are. That will cavitate the pump and produce air in the returns.

    Bookmark   March 21, 2008 at 11:05PM
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between the two 3 ways? the cleaner and the spa valves? i think it's just a straight pipe, though again, i'm not sure why, but it's necked down there to 2".

i still have to do the stop filter/squirting test. hopefully this weekend. i need to do a tiny bit of reprogramming ont he ps8 first though, right now the filter button will only let it go from high to low, not high to off...

thanks for the help as always, you guys have gotten me out of alot of jams.

    Bookmark   March 22, 2008 at 12:45PM
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if it's ok, i'm going to ramble some more...
here's the bubbles. i'm going with the assumption that these are too many/large to be from the salt cell. i've heard they can produce tiny but visible bubbles. ask because the bubbles are actually not there less than they are there. during an 8 hour low speed cycle, i don't seem to see them till about 6 hours into it. this could also be beacause the pump bucket is getting a little lower.

i also get about 30 min of bubbles after comming off of high speed. i know there has still got to be some sort of cavitation or suction leak due to me being able to see them all in the filter bucket vs. not seeing them in the bucket when the spa is on.

i did a couple runs of the quickly shutting off the pump and no joy so far.

i've definitely been wondering more about my builder...i kindof understand the 2hp pump with the spa, and i realize that for the most part, my pool only ever operates on low speed (even my cleaner works well on low), but wouldn't you go ahead and size the rest of the equipment to at least function with the pump? my skimmer (pentair admiral s20) has 2" ports and a sticker that says max flow 60gpm. so they had to neck it down to 2" from 2.5" right before the skimmer. there are a few neck downs in the suction by the pump too, the long lengths are all 2.5.

i did notice one other thing, i could run the pump on high with the equalizer valve out of the skimmer and noticed significatly less (almost no) bubbles in the pump basket. funny thing though, when i do it that way and kick down to low, i still get the same half hour of bubbles in the returns. i guess that's why i wanted to rule out the salt cell...

looks like i should start writing novels eh?

    Bookmark   March 22, 2008 at 7:24PM
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any of the builders know if occasional 2" neckdowns or reducers are common/ok in 2.5" suction systems?

    Bookmark   March 24, 2008 at 6:22PM
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any of the builders know if 2" reducers are common/acceptable in a system like this?

    Bookmark   March 24, 2008 at 6:33PM
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If it is indeed a 2" pipe in between that is common when the valves are that close. Sometimes unavoidable. Yours looks like a 2.5 coupler would have worked which would only slightly be better.

    Bookmark   March 24, 2008 at 9:10PM
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"My pool builder is trying to convince me that there is no way that there is a suction side leak and that the bubbles are being caused by cavitation"

That's quite interesting, in order to attempt to save himself on the leaks and air bubbles, and he is willing to hang himself by stating it is cavitation.

Cavitation is (as said earlier) caused by undersized pipes, and intakes in combination with pump selection.

So he is willing to admit he is destroying the pump and causing unnecessary energy consumption because of his design versus look for the leak????

    Bookmark   March 24, 2008 at 9:43PM
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