Puzzling water flow when pump is off

[Ed LaCrosse]

Hello all,

Apologies in advance for the long post.

I'm puzzled by the water flow in my pool's plumbing. When the main pump is running, all appears well, with no leaks visible anywhere near the exposed plumbing around the filter, pump, etc. I seldom need to add water except when it gets really hot, dry, or windy.

When the main pump is off, I hear gurgling sounds that suggest water is flowing out of the filter, back through the skimmer basket, and out to the pool, but I can't detect where in the pool any water is entering. Moreover, air is entering the water lines during this process. After sitting overnight, the skimmer basket has water up to the level of the input from the pool; i.e., it drains until it can't drain any more, with air filling the remainder of the basket. The gurgling sounds have stopped; no more water is running out of the filter. When the pump comes back on, it needs to re-prime itself, and every couple days or so, I have to bleed air out of the filter.

If I open the bleed valve on the top of the filter while the pump is off, air is sucked into the top of the filter as the water drains from it.

I'm trying to figure out where the air is entering the system and where the water from the filter is going when the pump is off, so I can "fix" it. Try as I might, I'm not getting it figured out, so I thought I'd stop by here to see if any of the experts can "solve" the puzzle for me.

I've attached a picture, below, of my exposed plumbing for reference.



Numbers in the picture correspond to water flows as follows:

1. Filter to heater
2. Filter from pump
3. Heater to pool and spa
4. To spa
5. To pool, fountain, vacuum
6. To fountain (note there is a check valve in this line)
7. Spa bubbler/blower (no water)
8. To fountain, after check valve (continuation of 6)
9. To pool, vacuum pump
10. To vacuum pump
11. To vacuum
12. Spa drain, pool skimmer basket, main drain to pump skimmer basket
13. From spa drain
14. From pool main drain
15. From pool skimmer basket

I've tried opening and closing various combinations of the Jandy valves when the pump is off and I get, to me, very confusing results. Examples follow.

If I close the valve at 12, presumably I cut off all flow back to the pool from the pump, but when I do, flow continues out of the filter!

If I close that same Jandy valve to 14 and 15, then flow stops. If I move that valve back to 12 and close the Jandy valve at 15 (theoretically prohibiting flow to both the pool skimmer basket an main drain, flow continues!

I've tried a few more combinations, but I'll stop here to seek any input or advice you folks might have. I'm willing to call in our pool service, but I really want to try to figure out what's going on, if I can, before I do.

Thanks for any insight.

 

[Newdude]

If I close the valve at 12, presumably I cut off all flow back to the pool from the pump, but when I do, flow continues out of the filter!

You should only be able to close off left and right, or any 25/75, 40/60 etc combo in between. Try it again envisioning that the handle is the base of a T. It should turn this way.



Another trick is to shut the pump off and pour water on the various suction valves while it's gurgling. If you hit the right spot, it'll stop momentarily.

A leak after the pump would cause a geyser.

 

[mas985]

When the main pump is off, I hear gurgling sounds that suggest water is flowing out of the filter, back through the skimmer basket, and out to the pool, but I can't detect where in the pool any water is entering.

The gurgling you hear is most likely just air rising in the filter. This is normal as air can get trapped by high flow rates near the bottom of the filter.

Moreover, air is entering the water lines during this process. After sitting overnight, the skimmer basket has water up to the level of the input from the pool; i.e., it drains until it can't drain any more, with air filling the remainder of the basket.

This indicates and air leak somewhere in the system

The gurgling sounds have stopped; no more water is running out of the filter. When the pump comes back on, it needs to re-prime itself, and every couple days or so, I have to bleed air out of the filter.

This is to be expected with an air leak.

If I open the bleed valve on the top of the filter while the pump is off, air is sucked into the top of the filter as the water drains from it.

This is normal since the valve location is most likely above water level so water drains back to water level.

I'm trying to figure out where the air is entering the system and where the water from the filter is going when the pump is off, so I can "fix" it. Try as I might, I'm not getting it figured out, so I thought I'd stop by here to see if any of the experts can "solve" the puzzle for me.

This is the hard part. Most common locations are pump lid gaskets, drain plug gaskets and suction side o-rings. The first two are easy to detect. Inspect the gaskets and use some pool lube and see if that doesn't help.

 

[Ed LaCrosse]

Thanks very much for the helpful replies. I had a look this morning before the pump came on and discovered that the skimmer basket in front of the pump was full of water; i.e., no (or very little air) leaked last night. This just adds to my confusion, because I did nothing to "fix" anything yesterday. I did have a couple questions on your replies, as follows:

You should only be able to close off left and right, or any 25/75, 40/60 etc combo in between. Try it again envisioning that the handle is the base of a T. It should turn this way.

The valve at 12/13 is, in the picture, closing off the flow from the spa drain. This is where I normally have it set unless I'm using the spa. I can rotate this valve 180 degrees counter-clockwise before it stops. To close off the flow to/from the pump (12), I can loosen the handle screw, pull up on the handle and move it clockwise. I do that to stop the flow of water (and leaves) back into the pool when cleaning the skimmer.

Another trick is to shut the pump off and pour water on the various suction valves while it's gurgling. If you hit the right spot, it'll stop momentarily.

I want to try this next time it starts gurgling, but I'm uncertain where the suction valves are. I assume you mean any valve, plug, or connection on the pool side of the pump. Do I have that right?

This is the hard part. Most common locations are pump lid gaskets, drain plug gaskets and suction side o-rings. Thfirst two are easy to detect. Inspect the gaskets and use some pool lube and see if that doesn't help.

Again, suction side refers to the "pool side" of the plumbing, right? The pump lid gasket sounds like a likely spot. The only thing I did yesterday was to remove that lid to check the water level in the skimmer basket. When I put it back on, I may have tightened it a bit and stopped the air leak, accounting for the full skimmer basket this morning. I've also suspected that the large filter O-ring needs to be replaced, but I get no water leakage around that area so I've discounted the likelihood that that's where the air is coming from. Is it possible for this O-ring to leak air when the pump is off but not leak water when it's on?

Thanks again for the helpful responses.

Edited to correct my interpretation of "suction side"

 

[mas985]

Again, suction side refers to the "pool side" of the plumbing, right?

Suction side of the pump refers to the section of plumbing, pool to pump, that is on the inlet side of the pump. This section of plumbing is usually under suction or below atmospheric pressure so any leak will draw in air.

On the return side of the pump, pressure is higher, usually above atmospheric pressure, so water tends to leak out when a leak in the plumbing occurs.

The pump lid gasket sounds like a likely spot. The only thing I did yesterday was to remove that lid to check the water level in the skimmer basket. When I put it back on, I may have tightened it a bit and stopped the air leak, accounting for the full skimmer basket this morning. I've also suspected that the large filter O-ring needs to be replaced, but I get no water leakage around that area so I've discounted the likelihood that that's where the air is coming from. Is it possible for this O-ring to leak air when the pump is off but not leak water when it's on?

Yes, leaks are not always reciprocal. So the plumbing can leak air in while the pump is running, on the suction side of the pump, while not leak water out when the pump is off. The pressure differentials are significantly different with the pump on vs off.

Also, any section of plumbing above water level will be below atmospheric pressure when the pump is off so will tend to leak air in.

 

[1poolman1]

Hello all,

Apologies in advance for the long post.

I'm puzzled by the water flow in my pool's plumbing. When the main pump is running, all appears well, with no leaks visible anywhere near the exposed plumbing around the filter, pump, etc. I seldom need to add water except when it gets really hot, dry, or windy.

When the main pump is off, I hear gurgling sounds that suggest water is flowing out of the filter, back through the skimmer basket, and out to the pool, but I can't detect where in the pool any water is entering. Moreover, air is entering the water lines during this process. After sitting overnight, the skimmer basket has water up to the level of the input from the pool; i.e., it drains until it can't drain any more, with air filling the remainder of the basket. The gurgling sounds have stopped; no more water is running out of the filter. When the pump comes back on, it needs to re-prime itself, and every couple days or so, I have to bleed air out of the filter.

If I open the bleed valve on the top of the filter while the pump is off, air is sucked into the top of the filter as the water drains from it.

I'm trying to figure out where the air is entering the system and where the water from the filter is going when the pump is off, so I can "fix" it. Try as I might, I'm not getting it figured out, so I thought I'd stop by here to see if any of the experts can "solve" the puzzle for me.

I've attached a picture, below, of my exposed plumbing for reference.

View attachment 631798

Numbers in the picture correspond to water flows as follows:

1. Filter to heater
2. Filter from pump
3. Heater to pool and spa
4. To spa
5. To pool, fountain, vacuum
6. To fountain (note there is a check valve in this line)
7. Spa bubbler/blower (no water)
8. To fountain, after check valve (continuation of 6)
9. To pool, vacuum pump
10. To vacuum pump
11. To vacuum
12. Spa drain, pool skimmer basket, main drain to pump skimmer basket
13. From spa drain
14. From pool main drain
15. From pool skimmer basket

I've tried opening and closing various combinations of the Jandy valves when the pump is off and I get, to me, very confusing results. Examples follow.

If I close the valve at 12, presumably I cut off all flow back to the pool from the pump, but when I do, flow continues out of the filter!

If I close that same Jandy valve to 14 and 15, then flow stops. If I move that valve back to 12 and close the Jandy valve at 15 (theoretically prohibiting flow to both the pool skimmer basket an main drain, flow continues!

I've tried a few more combinations, but I'll stop here to seek any input or advice you folks might have. I'm willing to call in our pool service, but I really want to try to figure out what's going on, if I can, before I do.

Thanks for any insight.

What you are describing is very normal for most pools the age of yours. As long as the pump has no issue priming and there are no water leaks it is not a problem. Air can enter through openings that are much smaller than water can escape through, even under pressure from the pump.

You can change and lube all the O rings in the system and you might stop this from happening, but the air leak can be anywhere there is a joint or gasket, or O ring in the above ground equipment. I count at least 22 different O rings in the plumbing in the picture. Then you have the various items inside the heater that are also fittings that could leak.

 

[Ed LaCrosse]

Also, any section of plumbing above water level will be below atmospheric pressure when the pump is off so will tend to leak air in.

Ah, yes! This is where I was getting confused. When the pump is on, it's clear where the pressure side and suction side are, but when the pump is off, then every thing in the picture above is below atmospheric pressure. All other pool plumbing is below the water level of the pool. Therefore, any air leak has to be somewhere on the pad with all the equipment and above-ground pipes.

One thing that I still don't understand is why do I get apparently contradictory results when I re-arrange Jandy valves when the pump is off (see above). I can arrange the valves so that the expected result is that water flow will stop but it continues. If I close the flow off at (12) then I shouldn't get any flow, but I do. Maybe one or more valves is leaking a bit?

Thanks for your insight.