Suction Leak - Do You Have One? Try a Big Straw!

Texas Splash

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TFP Expert
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Jun 22, 2014
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Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
DISCLAIMER: Safety First! Our pool is still CLOSED. The water is too cold so there are no swimmers, no risk to life or limb due to exposed suction pipe in the water. This was my own personal test conducted in a fenced/controlled environment for less than a 24 hr period. This was a temporary test only. If you attempt such a test, take necessary precautions. Safety is always a priority.

So over time we all inevitably wonder, "Do I have a leak, and if so, where?" Several years ago when I was TFP newbie, I created such a thread HERE. I came to the realization all was fine and I simply had a bit of OCD believing I should see a pump pot with absolutely zero air bubbles in it. Over the past few months however, the water level in my pump pot would fall by about 1-2 inches over the course of a couple days, then it would stay there. This was much different than years past. I never completely lost prime or went dry, but there was more air in the pot than back in 2015 when my system was new.

Last season I was trying to find a pressure side leak which you can read about HERE. During that adventure, it seemed as though my skimmer may have tilted with our horrible shifting/clay soil in the San Antonio area. You can see why I thought about the skimmer tilting by the angle of that pole sticking out of my skimmer in the pic below. That made me wonder if my skimmer line/connection may have cracked a tiny bit. I have a check valve and a 3-way valve ahead of the pump. I had already disassembled each, cleaned them up, and replaced all the O-rings. Last season I also disassembled my pump, replaced the shaft seal, and lubed all volute seals. The only thing left was the PVC suction line itself.

This brings me to the purpose of this thread. What other option do you have before getting out the pick & shovel? How about creating a new suction line? By bypassing your existing suction line, you can see if a new (temporary) line will result in an air-free pump pot, or if it stays the same. Basically a big straw. Yeah, it costs a few bucks for PVC and some fittings, but better than digging for hours only to find the line is fine right? So that's exactly what I did. Below are some pics of my test yesterday.

This pic shows the test suction pipe down in the water serving as a big straw. That PVC sticking out of the skimmer (tilted) was something I created last year to do a water pressure test on the line. Its angle is what gave me alarm to worry about sinking/shifting soil.
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Nothing fancy here. Just 40' of pipe going back to the pad. A big straw.
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Got myself a new union to connect to the pump. Loosened the fittings so that I could turn my pump a bit and connect the test line.
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A final view looking back towards the pool.
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So what were the results? Did the new test line result in an air-free pump pot confirming my original (ground) suction line was cracked, or did air still get in the pump? The result - no change! Air was still getting in the pump pot. This was good & bad. The good was now I see no need to dig-up the ground to get to my skimmer connections which would've been an exhausting job to say the least. The bad part is I still seem to get air in the pump pot. A bit more than I would like perhaps, but I'm not losing prime. My pump is going on 9 years now, so perhaps something warped a tiny bit over time that an O-ring or pool lube can't seal. Regardless, I go out to the pad at least once a day anyways to purge air, so it's no big deal.

Best part about this test project is that it kept me from chasing something that wasn't there. So if you have doubt about a suction side air leak and have ruled-out everything but the line itself, you might create a test line ....... basically a big straw. Good luck.
 
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AWESOME write up Pat !!!

I'd like to point out the (not always so) obvious to respect the safety needed while the non VGB compliant suction setup is in place. If a leak is proven, it may be left in place until next weekend or whenever the DIYer has the time to investigate further. The kids will want to swim in the meantime so be sure the pump is off at those times.

Do not leave anything to chance.
 
I hate the “twist to seal” lid designs on pumps. Pentair uses it too. They are made that way for easy access but, as @Oly alluded to, they seal like garbage. I have actually taken a very fine grit sanding sponge followed up with polishing paste, to smooth out the sealing surface on the pump wet end. Then I have lubed up the o-ring with a bunch of silicone to make it seal properly. Even then, I can still detect an occasional air bubble. It also seems to be an issue with low speed VSP’s that they can’t keep their strainer pots full. I have a single speed WhisperFlo (1.5HP) that runs my waterfall and it sits right next to my IntelliFlo. The WhisperFlo pot is completely full with not a single air bubble in it whereas the IntelliFlo will have the “bouncing bubble” in the pot all day long.
 
Pat,

Using the "Big Straw" seems like the only sensible thing to do as a test before digging up the yard and under the deck for a non-existent problem. :goodjob:

I have noticed that as my filter gets dirty, the low speed bubbles under my pump lid get bigger and bigger. And I have a big cartridge filter. I would assume the same would be true for you, only worse, with the size of your filter.

Maybe you should move the Big Straw to the output of the pump and see if your bubbles go away.

Thanks,

Jim R.
 

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Great write up!
I have a concern that my pump lid has possibly warped in some way over the winter.
It was leaking, cleaned everything & lubed the oring and it was better for a day.
Ordered a new oring, better but I still have to tighten it like the hulk 💪 or water pours.
I may try my old pump basket lid (if it will fit- they changed the design) before ordering a new one but I can’t see another solution/reason. There are no obvious cracks on the lid or pump itself.
 
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I wouldn't worry about safety of the suction since this only a test of the system.

Btw your straw could have suction leaks as well so to be 100% sure take it out cap the ends and vacuum test it with a vac pump and a guage and valves. Rare but possible. You can also use this vac test equipment to test your underground piping as well.

It's highly unlikely but there are leaks that will hold pressure but leak on vacuum, I've seen them before with 3400' of threaded tubing.
 
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And, it drives you crazy.

You go out every 30 minutes checking to see if it is still there and it is and you feel like it's mocking you.

It does … along with all the voices in my head … they just keep mocking me ….
 
I wouldn't worry about safety of the suction since this only a test of the system.
C'mon now. We all know people will prove their leak, then leave the straw in place.

The test will become a temporary suction line, for anyone who's leak/clog was bad enough to take the pool equipment out of service.

Whether it's one week until the pipes are located, dug up and repaired, or four weeks........ horrible things can happen in the meantime.

For anyone making a T or multiple points of suction, they need to be far enough away from each other that you can't touch them both/all.
 
I have noticed that as my filter gets dirty, the low speed bubbles under my pump lid get bigger and bigger. And I have a big cartridge filter. I would assume the same would be true for you, only worse, with the size of your filter.
Absolutely. My pump typically does the same thing when dirty. Since I don't have a MPV, one of my troubleshooting steps was to remove the cart filter altogether to eliminate any resistance, but it still did the same thing. :(
 
You can pressure test the lines.
I did try that to some degree a few months back with that PVC tool I made. I pushed about 20 psi of water into the line. My problem was I didn't have a good expandable plug at the pad end, so I was relying on the 3-way valve to try and retain pressure at the pad. I slowly lost pressure, but very little. I chalked it up to not plugging good at the pad until recently when I felt more air was getting in the pot. Then I started getting a bit paranoid. Hence, the straw line test which gave me more assurance the air was seeping into the pump pot alone. Either there's a tiny compromise at the inlet, shaft seal, or lid that I just haven't nailed down. Hard to imagine as I've torn it apart dozens of times and slathered every seal like crazy, but the amount of air getting in there is not worth the trouble any longer.
 
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Just so everyone can sleep good tonight, I removed the test line at first light this morning. Pool is fenced off, no children around, and no one has taken the plunge yet this year since our water is still a little too chilly. We've become spoiled here in Texas and demand water temps of ~86-88 degrees. Ha ha.
 

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