Leak in one return jet

[dpl252]

Hey folks, my pool has been losing water every day so naturally I suspect a leak but there are some odd symptoms I’m hoping you can help explain.

Every day I lose maybe an inch, bucket test confirms not evaporation. The water drops to almost the bottom of the skimmer entry (but not quite) so I naturally suspect either a crack in the skimmer near the mouth or structural crack in the concrete. Spent an hour with some dye, no movement in the skimmer whatsoever.

Then it dawns on me, since I moved into this house a year ago and fixed up the pool there has always been 1 return jet, furthest from equipment, that has no flow, all other jets are fine (5 total).

I then do a bucket test again, 24 hours with pump on, then again with pump off. No water loss when system off is it appears to be pressure side. The odd thing is, when my pump turns on and primes, I get bubbles out of this jet (all my jets have some bubbles during prime, then normal flow). This jet just shoots bubbles during prime, then no flow at all. Since my water drops only down to a certain point I feel like the leak is probably near the return itself (it drops to maybe a few inches above the return.

Any further tests I can do? Should I do a dye test on that return while the pump is on so see if the fitting is leaking? Why would bubbles come out but then no flow, maybe there’s also some blockage?

 

[dpl252]

Forgot to mention that filter pressure is normal, some small bubbles in pump, mostly when priming but otherwise it looks okay. I just cleaned my cartridge filter 2 weeks ago so it's pretty clean.

 

[Texas Splash]

This seems a bit unusual. Are you sure that mystery jet is actually a return jet? Since there were previous owners, I wonder if a repair was done before, or if perhaps that jet is for something else. It's also possible you have more than one thing going on. You may have a tiny suction side air leak resulting in the bubbles which may have nothing to do with that one jet or your suspected water loss.

How about posting some pics of the equipment pad, pool, the jets, etc. More visuals may help.

 

[dpl252]

Here's a video of the return jet in question (it's definitely a return jet):

https://imgur.com/a/9z7jLaV

The video shows my pump (VSF 3.0HP which is self priming) turning on. All the other returns have big bubbles as well during the prime but then have normal flow, this jet takes much longer to react (like a good 10 seconds, maybe because it's the furthest away?) but just spews smaller bubbles, eventually the bubbles subside but then no flow at all.
Also there is a video of my pump basket which has one large bubble in but otherwise flow seems good, I know the basket has some debris, I clean it regularly and use a skimmer sock to help with debris. Filter pressure is normal, I just cleaned it a week ago.

 

[Texas Splash]

Being at the end of the return branch line would certainly explain why it takes longer to purge. The two big questions are:
1 - Why is there that much air to begin with?
-- This indicates air is getting into your plumbing system from somewhere. That could be at the equipment pad. If there was a break at/near that return jet, I would think there should be some evidence of moisture around the pool area.

2 - Why does water flow stop at that jet?
-- That is puzzling. I thought of a partial obstruction, but you said you use a skimmer sock, so nothing should've made it past that. If there is a plumbing break near that last jet, again, there should be some wet ground nearby. Do you have any way to attempt a pressure test of that pressure line?

 

[dpl252]

We had our pump replaced when we moved in, the old pump was severely corroded. I'll see if I can do a test on the suction side plumbing before the pump to see if there's any air getting in.

If there's a leak near that return, if I turn off the pump and do a dye test right at the return would that show the leak? It's confusing because my water level only dropped when the system is off. If the leak was small enough that the water line doesn't noticeably drop in 24hours when the pump is off, would is also explain how it drops like almost an inch a day when the pump is on?

 

[Texas Splash]

To do a dye test on the return jet/line, you would want the pump off to see if dye gets pulled IN towards the line behind the wall.

 

[Newdude]

If the 5 returns are all on the one pipe, or even 3 of them, the last one may not have any oomph once the RPMs lower after priming.

 

[dpl252]

If I were to pressure test this line, should I plug all the other returns and then put a gauge on just that return?

 

[Texas Splash]

When my line was tested, they plugged all return keys and pushed air from the pad.

 

[dpl252]

Got it, I think I know enough now to have people come in and do proper testing and diagnosis as I think I'm beyond DIY on this. Thanks for the help!