Bubbles from suction side and pump loses prime overnight

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N

NathanT

0
Mar 18, 2016
14
Victoria, BC
Hello,

I'm a new pool owner, as of about May 2015. I'm fairly confident we have a suction side leak, but I don't really have a basis for how much air getting into the system is "OK" (if any), and would love some guidance on what to try from here. I've made a couple videos to demonstrate what's going on.

The pump is a 2HP variable speed pump, and it (along with the filter and other equipment) sits approximately 4-5ft above the pool surface, and about 30-40 feet away. There is also a solar system with a check valve on the return, which has been winterized (blown out with air). (The rest of the system has been left running over the winter, since the weather here is mild, only occasionally dipping below freezing.)

Since the pool was first opened we've been having problems with air getting into the system whenever the pump is shut off for more than a few minutes. Our pool contractor has re-sealed several joints, added a check valve before the pump (on the suction side) and most recently replaced the pump housing. These have improved the situation, allowing the pump to be off for longer without the water completely draining out. However, if it is left for a few hours, most of the water will still drain back into the pool if left off for any period of time. Also, if I bleed the air out of the filter pressure valve, even just a few minutes later there is a significant amount of air built up to bleed out again.

Looking at the pump basket or the check valve before the pump, I can see a continuous stream of bubbles flowing with the water. (There are also continuous bubbles in the pool returns.) What I have noticed most recently is that there are considerably more bubbles coming from the drain line than from the skimmer. This video demonstrates: Suction side leak - YouTube

Also, when I shut the pump off, I can hear bubbles coming up from the drain line. So my understanding is that either the leak is in the first part of the L joint, right after that pipe comes out of the floor into the equipment shed there, or that it's underground somewhere. (I'm hoping the former, obviously.) However, I can't hear any air being sucked in there. With past leaks I've been able to hear it hissing in. I can't really do the trick of pouring water over it as it runs, because it would flood the shed.

So one question is, how likely is it that it's underground? I would think that even if a pipe was leaking underground, there would only be so much air for it to pull in, since it would be surrounded by dirt.. but maybe I'm totally wrong there. Regardless, I guess the first thing to rule out would be the joints up to the suction side valve here. Is there a way to test them without flooding the shed?

Also, after taking that video, I've noticed that even if I have that valve set all the way to the skimmer side, there are still some bubbles flowing in, just not nearly as much. This, for instance, is with the valve all the way to the skimmer side (drain line completely shut off): Skimmer air - YouTube

It seems intermittent though, for some reason. Also it's not as bad if I turn the pump speed down. Still, even with the drain line shut off, after running for a few minutes, I can bleed a bunch of new air out of the filter. The top of the pump basket slowly fills up with air too. So.. is that normal? Or would it be considered a problem too, even without the larger amount of air coming from the drain side?

Finally, while doing this troubleshooting, I noticed a strange rattling coming from the valve, only at certain positions: Valve sound - YouTube Sounds like maybe something got pulled in and is now stuck in or next to the valve? Should we open it up?

One last thing. Whenever the pump is shut off, a large stream of bubbles is sucked out of the check valve on the way back from the solar. That makes sense since it's full of air, and when the pump is shut off there will be a vacuum on the pressure side of the system (especially since everything is a few feet above the pool). What's odd to me though is that this happens every time the pump is shut off, and has all winter. Theoretically the solar system should all be sealed, so even if some air could be sucked out, you would think eventually it would be at a bit of a vacuum, so it wouldn't be possible to keep sucking more out. So I'm thinking what must be happening is that while the pump is running throughout the day, a small amount of water is leaking back through the check valve into the pipe that runs from the solar. Then when the pump shuts off at night, air is sucked back the other way. Either that or there's yet another leak in the solar that's letting air get in there as well. What do you think, and is it worth worrying about? I don't think it's related to the problems mentioned above, since this is on the pressure side, and the air definitely seems to be entering on the suction side, but I'm wondering if it's another issue. Our pool contractor says if we want he could add a manual valve after the check valve, for winterization.

Thanks in advance for any advice!
 
Hello Nathan and welcome to TFP. Thanks for the videos. In short, I believe you either have air getting into the system, or perhaps something impeding flow. Definitely too much air in that pump strainer basket while running on a higher RPM. While it is somewhat common to hear of VSPs that have a small amount of air trapped under the lid at a low RPM, that usually gets pushed through once the speed is increased. To pull more in when increased would tell me that it's either letting more air in somewhere, or that a blockage is slowing-down the flow of water. That sound in the valve is troubling. Perhaps s rock or something made it past the skimmer basket at the pool or got ingested during vacuuming and got stuck in there. But I don't like the sound of that, so you may need to pol that valve apart and inspect.

Since you don't want to pour water on things your shed, you might try some smoke around joints to check for an air leak. Maybe light a cigar or some incense, then go around each joint and see if the smoke gets pulled-in. Just incase you haven't already been here, try this page for any last-minute ideas: Pool School - Suction Side Air Leaks.

Try there first and let us know how things turn-out. In the majority of cases, an air leak is above ground. So I would focus my attention there and with everything on the link I gave you. Try the smoke test, or some foam shaving cream (although that's a bit messier). Hopefully we can help you pinpoint that source of trouble. Talk to you soon.
 
Thanks! Just to make sure I understand, when you say it could be caused by a blockage, is the idea that if one of the suction lines was (partially) blocked, it would create increased suction between the blockage and the pump, which could be enough to suck air in somewhere that it wouldn't come in under normal suction levels? If I'm understanding you correctly, that isn't likely the issue, because this isn't only a problem when the pump is on. When I shut the pump off overnight, all the water slowly leaks out of the system. So even the amount of suction caused by gravity and the 4.5ft rise from the pool to the pump is enough to suck air in.

Last night I left it overnight with the pump off and the valve turned all the way to the skimmer line, so the drain line was shut off. For the first time ever, there was no air in the pump basket in the morning. There was a small amount of air in the line when it started up, but that was cleared out in a few seconds, as opposed to the several minutes it usually takes. The drain line though was completely full of air and took some time to clear out once I opened it back up. So that appears to confirm the problem is on that side.

I'll see if I can find some incense or something to try the smoke trick...
 
Well, you certainly appear to have made very good progress by isolating the main line overnight. Unless there is a portion of the main line fitting exposed at the shed, it may be difficult to find the leak location. If you become convinced that the main drain line is the culprit, and that it's letting air "in" when the system is on, then it should stand to reason that when the system is "off", it might let water seep out of that location. "If" that were the case, you might see a potential water loss if it was a big enough leak. Personally, my other concern would be for your base material. My pool was backfilled with sand, so I wouldn't want water compromising that base - that's "if" it is leaking under there somewhere (it may not). But you can easily run your pool with the skimmer only, although having a new pool barely only 1 year old, you probably aren't thrilled with that idea. But the pool will be fine. I operate my Viking Poseidon with just one skimmer. Keep us posted on your progress with the smoke tests. It would be great if you founds a spot at the shed that could be fixed easily. Have a nice weekend.
 
The pool certainly doesn't seem to be losing any water, so presumably the leak is above the water line. (Which makes sense because, as mentioned, the pump and everything is several feet above the pool, so most of the plumbing is as well.) I just tried shaving cream around the joints in the shed, and didn't see any signs of an air leak there.

The crazy thing is, even if I switch to the skimmer line, there are still SOME bubbles coming through, just not nearly as many. Maybe they're coming through the valve (hopefully!) and the only leak is on the drain side. Otherwise I guess there could be leaks on both sides? That seems unlikely unless the PB was doing something wrong.

In the past our PB has suggested just running the VSP on low overnight to prevent it losing prime, saying that some bubbles in the returns aren't a problem. But from what I've read here, it's not a normal thing. Also, I'm concerned about the air building up in the filter. Any time the system runs for more than a minute or so, I can bleed air out of the filter for a good 10 seconds. So basically it's always running with some air in there. Is that a problem?

I'm not crazy about the idea of just running the pump 24/7 to work around this problem, but I'm not crazy about the idea of digging up the whole yard either, so that might be a lesser evil, if it's not going to cause problems to always have air in the filter.
 
It is not uncommon for VSPs to retain a small amount of air in the strainer basket when on a low rpm. But having to bleed that much air (10 sec) doesn't sound good. Your video captured the air gap well. Just to make sure ... have you exhausted all the items on the suction side troubleshooting page? Especially taking a close look at your strainer basket lid O-ring and the VSP drain plug seal(s)? Earlier when I noted a concern about suction blockage, it wasn't so much about creating additional vacuum, but just simply blocking flow to the pump which in-turn may prevent the water from keeping-up with the VSP's pull - more like starving the pump. That's what also concerned me about that noise in the Jandy valve. While there are always exceptions, the most common reason for air accumulation in the pump basket is a suction side leak. Getting a little air trapped while on low (possible out-gassing) is acceptable, but losing half the strainer basket level while on high (like on your video) is not. Additional plumbing with heat, solar, and SWGs can contribute to some unusual occurrences, and sometimes produce a little bit of air out of a return jet, but should have no bearing on the strainer basket air since they are after the filter. Those items however, just like your filter housing, can effect water (pressurized) flow when the system shuts down if there is a breach somewhere.

At this point, as if you haven't done it enough already :brickwall: , I would continue to check all fittings, and even your filter gauge/housing seal for suspected leaks. You may have two issues going on - a suction side leak contributing to air in the basket while running, and another issue somewhere that is equalizing pressure and allowing water to drain-out once the system is turned off.

If this continues, I may suggest posting some pics of yoru equipment (to include the heater/solar/SWG) and ask for some others to review this specific thread for assistance. Hang in there. We'll get it.
 
The whole pump basket was just replaced - it was leaking air before - and that significant increased how long it took for all the water to drain out when the pump was turned off, but didn't solve the problem entirely. I'm thinking the leak (or at least A leak) must be before the pump, because I can see the stream of bubbles in the check valve, which is before the pump. Also, since it drastically decreases when I shut off the line from the main drain, it suggests that there's a leak in that line.

Regarding a blockage, I think we're describing the same thing in different ways. If not enough water can be pulled to handle the pump's flow, it will by definition increase the vacuum, which would either force the pump to slow down (or burn out) or pull air in from somewhere to make up the difference. Anyway, that doesn't appear to be what's happening here since we get the bubble stream at any speed, and air appears to be pulled in even when the pump is off.

Unfortunately since I've ruled out the connections in the shed, I guess the next step would involve digging. So I'll have to convince my PB that this needs to be done (under warranty).
 
I would suggest a pressure test of the lines in question. Pressure test the skimmer and main dain lines including all of the way to the pump.

Plug the main drains and the inlet of the pump and then connect your test rig in the skimmer bottom. Pressurize to about 15 psi. If it's leaking, the pressure will noticeably drop within a few minutes.

If it's leaking above ground, you will see where.

If it's leaking, and not above ground, then you do the lines separately.
 
JamesW said:
I would suggest a pressure test of the lines in question. Pressure test the skimmer and main dain lines including all of the way to the pump.

Plug the main drains and the inlet of the pump and then connect your test rig in the skimmer bottom. Pressurize to about 15 psi. If it's leaking, the pressure will noticeably drop within a few minutes.

If it's leaking above ground, you will see where.

If it's leaking, and not above ground, then you do the lines separately.
Click to expand...

Thanks for the detailed suggestion. It's funny, I was just doing some research and came back to ask whether it would make sense to do a pressure test at this point... and then found your response! And that makes sense testing the skimmer and drain lines together like that to start with, since it can be done without dismantling anything. Assuming that first test fails (I'm pretty confident it will, but we'll see) how would one go about testing the lines separately? The skimmer line would be easy enough since you could shut it off and test from the skimmer side, but for the main drain, I guess to avoid cutting the lines you'd have to have a long hose for the pressure tester and connect it to the drain itself?

Either way we'll have to wait a few weeks until the weather is warmer to get down to the bottom of the pool without hypothermia setting in...

Also, pressure testing with water (as opposed to air) is standard, right?
 

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To test just the main drain, you could close the valve going to the skimmer and pressure test from the pump inlet. There are unions on the pump, so it's easy to move the pump out of the way.

You would have to remove the check valve flapper to allow pressure to go back to the drain. If it holds, you're good. If not, it could be a leak at the three-way valve. If it leaks, then you might have to cut the line and pressurize the line directly to eliminate the valve as the source of the leak.

You can use air or water, whichever is easier.
 
OK, we were finally able to do a pressure test, and confirmed a slow leak from the main drain suction line. PB says he tested it with water at 30psi,and it lost about 1 litre per hour.

Unfortunately he says a leak that slow is going to be impossible to track down, so the only real option would be running a new line, which would mean digging up half the yard, tunneling under concrete, etc. He's suggesting just shutting off the drain and running skimmer only. After spending all this money on the pool though, that sounds a bit to me about buying a brand new awd luxury car that ends up not driving the front wheels. Sure it'll work, but it's not how it's supposed to be.

Now, because it's pulling in air rather than leaking water when the pump is off, we know that the leak is above the water line. There are only two connections in this line above the water line. One near the pool, and one directly below the pool shed. My guess is that the latter is leaking, but I think I can confirm that without digging. Here's my idea:

Fill the pipe with water, up to near, but not past that top connection. (Ie blow it out with air, then plug the drain and pour water back in, measuring how much it holds, then repeat, leaving out enough for the top connection to still be in air, or something like that.) Then pressure test with air. If it leaks out at the same speed as when the whole line is full of air, the leak is at the top. If it's slower, it's further down. (The leak is covered with water, and so will leak slower at the same pressure.) Makes sense?
 
As long as it makes sense to YOU. :hammer: ha. Actually, you've put some thinking into it I can tell. I hope you can solve this riddle. In the end though, if it doesn't work-out for some reason, your pool (luxury car) will be just fine without the main drain. Yes, hind-sight is 20-20 and all, but it will. But if you do get it resolved - great! Best of luck.
 
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