What's Worse: Suction Side Air Bubbles or Skimmer Leak?

[Frenchie250F]

I'm a new pool/home owner, and after spending a bit of time getting to know my pool system I've noticed that the ~3/4" - 1" of water I loose per day seems to be high, even for central FL with a solar heater (pool/spa is smallish, ~11,000 gallons according to the SW model I threw together). So I dove into some reading on identifying pool leaks (thanks to many on this forum already...) and have noticed a few things:
1) There are some bubbles finding their way out of the pool jets, my understanding is that this usually (always?) indicates a suction side leak. However, I'm also understanding that a suction side leak isn't necessarily the source of noticeable water loss, just a suction side leak.
2) If I shut the intake valve for my main drain and only run the skimmer intake, I don't see any bubbles coming in through the jets, or any bubbles in the pump basket. If I reverse this (open the intake on my main drain and shut the skimmer) I see a consistent stream of small bubbles coming out of the jet, and the pump basket has a steady ~1" of bubbles swirling around the top. This leads me to believe that when I pull a large amount of suction through the main drain line, it is pulling more air into the leak, and the leak must be somewhere on that line. Note that this is all independent of the large amount of air that comes out of the system when I first start the pump (since there's a vacuum release on the solar roof heater). The pump also primes almost instantly.
3) Some of the tile and grout around the skimmer box is in need of some repair. I'm not sure if this is just a red herring, but there's enough gap ~1/8" in the grout/concrete that I could see a noticeable amount of water escaping there, even with little/no pressure. Given the drought we currently have in central FL, the sandy ground that I presume is under my concrete sucks up water like a sponge.

So my question is... Is it worse to run the suction through the main drain with the air leak that I suspect, to diagnose a possible water leak at the skimmer? Or should I focus on diagnosing the possible air leak at the main drain by running the skimmer only and ignore potential water loss at the simmer intake?

Or am I way off in all of my concerns and diagnoses?

 

[gwegan]

I suspect (but don't know) that you have a leak somewhere in your main drain line. When the pump is turned off it leaks water out, when the pump is turned on it pulls air in.

I would first do the bucket test to see if you have a leak. If you do I would then do a dye test around your suspected skimmer leak do this with the pump off. Try it a couple of times on different days. See the links below

If that turns up negative (as I suspect) then I would hire a leak detection co to find your leak in the main drain line. 3/4 to 1 inch is a lot of water over time.

Pool School - Suction Side Air Leaks

Pool School - Leak Detection

 

[Frenchie250F]

I should have clarified, the water loss measurement (~1") is from a bucket test. I've been keeping an eye on the general water level and the water in a 5 gal bucket set into the pool over the past few days. I've been keeping a rough average of the difference in level between the two, which is where the 1" comes from. Due to some other complications (there was a small leak in my roof solar that I fixed a day or two ago), I haven't kept a hard day by day measurements in excel, but probably will now that I've eliminated other problems.

I've read those two articles on here before, but admittedly haven't started the step by stem elimination process for suction side air leaks; only picked up on the fact that I'm likely looking at a suction side air leak. Once I get the pool chemistry under better control (we had a pool store doing it between closing/move in, I suspect they didn't shock it a few times as their record claimed...) and can shut my pump for a day every now and then, I'll start trying to work through potential leak components, with a focus on the main drain line.

I guess what I was looking for is an overview, or comparison, of the potential damage that could be caused by chasing one problem vs. the other.

From the sounds of it though, I could get a better sense of the potential at the skimmer with a dye test. If that shows up negative, or at least not substantial, I know to try to keep the pump running on the skimmer and spa drain until I can locate the leak in the main drain line, which I hope is near the pump pad. I wanted to dig up those pipes anyway since there's an old heater and some old auto-chlorinator pipes that may/may not still be in the system from the old owner. The water loss is definitely a lot of water, and having just had the drought follow me when I moved from CA to FL (hope you're enjoying the rain...), I'm fairly conscious of water use (and after a home purchase, also conscious of water bills...). Intuitively to me, it seems like running more suction through a line that already indicates a potential leak would be more damaging than some water leeching out of a wall.

Thanks for the pointers. I'll run with the dye test over the next few evenings and see what ends up happening.

 

[gwegan]

I don't want to sound like a shill for the leak detection industry and I have no idea what your setup looks like but I'd call around and find out how much basic leak detection costs -- before I start exploring.

 

[Frenchie250F]

Noted and thanks. Its somewhat comforting to hear since I've been getting mixed opinions on using "professional" leak detection service, though I assume like anything else there are some people who are great at their jobs, and others not so much. I'll check around the neighborhood to see if there are any local recommendations.

In the meantime I'll still do some light digging around the pump pad unless that's a particularly bad idea; I don't plan on attempting to "explore" too far down or near the concrete deck (~10 ft away). That area of my yard needs regrading, drainage issues there, there are old cables (all old cut coaxials I assume were for satellites, though I have put in for a utilities check just in case), an old chlorinator, and an old gas heater (original reason for the 811 call). The pad may have settled a bit with the drainage problem, so I'm hoping I'll find the leak at a joint nearby. If not, I'll concede to calling someone to to a more thorough search.

 

[Frenchie250F]

In case anyone ever digs this up...

Turns out in this case the skimmer leak was worse. Ended up finding a few small leaks on the pressure side (booster pump line) and a a few touchy valves on the suction side. Patched them up with no noticeable difference. Fixing ~2" of grout/seal damage at the skimmer intake was apparently enough to clear up 1" per day of water loss.

May not apply to all setups, but my lesson learned here was any suspicious looking grout at the skimmer is worth a few bucks and a day to patch it up as a starting point.