Need help making sense of this plumbing so I can troubleshoot my pump losing prime.

[reidm]

I've had my house for about 2 years, and started using TFP this year. What a game changer!

I have a problem with my pump losing prime. I've suspected a suction side leak for some time underneath a mid-sized spruce tree near the skimmer (intermittent sucking/gurgling sounds), but no real problems... until yesterday. I'm hoping there's a new leak somewhere at the equipment pad, and not an immediate need for tree removal and excavation...

If I fill my pump basket with the hose, close it, and run the pump, I see bubbles coming from my drain and one of my 3 returns, but none in the pump basket, then within 15-20 mins, the pump loses prime.

I know I'll need to check my rings/gaskets, but when I started thinking about how to isolate the various parts of the system to locate the leak, I realized I didn't understand it. See photo.

The 3 suction side valve handles have labelling on them indicating they are for the skimmer, vacuum line, and drain, but I don't understand (1) Where the vertical pipe in the ground is coming from, (2) why the drain line is connected to the suction and pressure side of the system, and (3) why there are 2 lines on the pressure side.

I found a "cheat sheet" left by the previous owners (see photo), and it seems to indicate that this plumbing might allow for the drain to act as both suction and return, so that heated water can be sent to the bottom of the pool. "Heat" is only supposed to be open when "Pool" is off, and v.v., and never both closed at once... There is no labelling on the 2 return lines, but I suspect that is what they meant by "Heat" and "Pool". I've yet to ever open my drain cover ... Should I expect to find 2 openings beneath the cover, or are those lines more likely to merge somewhere underground? Or am I completely off the mark here, and something else is going on?

 

[PoolGate]

My neighbor's pool the main drain can be set for suction or pressure. There is only one line going to it. It can help the pool to heat quicker if it's set to pressure and heated water is allowed to return to the pool via the main drain.

 

[Jimrahbe]

Reid,

If I had your pool, I would leave the valves set up as they are in the pic..

Your suction to the main drain is shut off and the main drain is now connected to the pressure side return water.

There is really no need for the typical suction side main drain.

The pipe with the "?" mark and the blue line is the one connected to your main drain.

Thanks,

Jim R.

 

[reidm]

Your suction to the main drain is shut off and the main drain is now connected to the pressure side return water.
...
The pipe with the "?" mark and the blue line is the one connected to your main drain.

Thanks Jim. What's still got me confused is that there appears to be a suction line coming up from the ground and tee'd to the right of the line labelled "Drain." I assumed it would go to the drain, but wouldn't that mean the drain is always sucking, and closing the DRAIN valve would only lead to no water movement in the drain line? And furthermore, if it does indeed go to the drain, do the two drain lines join somewhere, and if so where?

Or does that pipe go somewhere else? I can't fathom where...

Later tonight I'm going to excavate it a bit to see if there's a valve or cap or anything at all to indicate its purpose.

 

[Jimrahbe]

Reid,

Most pools only have three things connected to the suction side..

1. Skimmer(s)
2. Main Drain
3. Vac Port

In your pic I see all three...

I suspect that they just capped off the pipe going into the ground and are using it to support the valves above it.. I could be wrong, so it would not hurt to dig a little.

I re-read your initial post and it sounds like you are looking for a suction side leak.. Then you say you think you have one near your skimmer. The entire suction line is under a vacuum.. So if there is any crack or opening in the pipe, it will allow air to come in.. I suggest that you find and fix that issue. before looking anywhere else.. As a test, make sure your Vac port it open to the pool, and then close off the skimmer valve.. If the pump can run sucking water from just the Vac line, without losing prime, then there is an issue with the skimmer line.

Thanks,

Jim R.

 

[wireform]

It's basically process of elimination, shut two and leave one open to see which one will be the cause of the air. But, there's one more choice and that's with the main drain valve. Besides eliminating the MD valve altogether you can also see if leaving open "A" and closing "B" if that stops the air too then you just won't use the extra loop.

 

[reidm]

Oh boy, do I have an update.

First, I did exactly as suggested and closed the skimmer line, opened the vac port, and also opened the main drain on the suction side and closed it on the return side. So far, it's gone many hours without losing prime. I've also noticed that the jets are much stronger now than I've ever seen them. Makes sense I suppose.

So as you say, clearly there's an issue on the skimmer side. I'll put the drain back to pressure to make sure that doesn't cause loss of prime, but it seems unlikely it would.

Now, I removed a large spruce near my skimmer, where I'd been hearing some gurgling. Turns out it's (probably) unrelated: a previous owner had installed a VERY sketchy sump (I know!), the spruce had grown over it, and the pump sucking air at the end of its cycle was the gurgling I was hearing! So I'll be decommissioning that...

But when I excavated the elbow, Darn if I didn't find another valve (see pictures)! No indication on it at all what it's for. I did notice, though, that the line going to it is smaller than the other 1.5" lines. I think it's 1". It was in the off position when I excavated it, so it's been off for many years. The dirt around it definitely hadn't been disturbed in a long time...

I want to eventually get this whole thing re-plumbed above grade, probably with diverter valves, but first I want to understand it, and find this dang leak. I'm going to start with the O rings in the valves. I'm also going to open up the main drain cover to see if there are two pipes going to it. Maybe that's where that 1" pipe goes, as a dedicated suction line. I can't really fathom where else...

 

[Jimrahbe]

Reid,

Unbelievable!!!

Do you have two skimmers???

Do you have some kind of water feature that has its own return?

Unfortunately, flex pipe is known for underground issues...

This means that the problem in the skimmer line could be anywhere along the line.. Most likely at a connection, but could actually be anywhere...

One of our Mods, had this same issue.. As a temp fix, and just to make sure the skimmer line was bad, he ran an above ground pipe from the skimmer valve to the pool. Basically by-passing the skimmer completely.

Thanks,

Jim R.

 

[reidm]

Do you have two skimmers???

Do you have some kind of water feature that has its own return?

Unfortunately, flex pipe is known for underground issues...

This means that the problem in the skimmer line could be anywhere along the line.. Most likely at a connection, but could actually be anywhere...

One of our Mods, had this same issue.. As a temp fix, and just to make sure the skimmer line was bad, he ran an above ground pipe from the skimmer valve to the pool. Basically by-passing the skimmer completely.

Just the one skimmer. No water features. Maybe there used to be one? Might be something I'll discover when the time comes to replace the vinyl liner... There is an odd circular-shaped "something" beneath the liner at the bottom of the deep end near the drain. Maybe 3-4" diameter. I always figured it was a flaw in the pool body. Maybe I used to have 2 drains... But it seems an odd spot (not centered in the deep end in any way). See image. Don't mind the detritus at the bottom... I don't want to vacuum all that right into my pump basket.

It's also worth noting that the sump I found was plumbed with pool pipe. I think that's coincidence... It's not pointing toward the suction manifold and it just wouldn't make a lick of sense for it to be going there anyway.

Thankfully, my skimmer line isn't terribly long. Maybe 20ft, max. It shouldn't be too hard to excavate if need be, save for the section that will surely be full of tree roots. Of course, that's probably where the problem is... Maybe if I scope it I can triangulate the location of the failure. Sounds like a good idea to convert to rigid PVC if possible before backfilling.