Infinity Edge Pump loses prime overnight

[garin33]

Hello everyone,
I have an infinity edge basin / vanishing edge basin that has a 1 HP Pentair pool pump that pumps water from the basin to the pool. It does not go through the filter, heater, multiport valves, etc so the plumbing is very simple. It has been working fine until last week when I noticed that it would lose prime overnight. That wouldn't be a big deal but because the infinity basin is very far from the pump, it takes about 8 minutes to prime the pump. It has been like this since the day the pool was installed about 13 years ago. Note that the pump and motor was replaced with a brand new Pump and motor about two years ago.
I changed and lubed the O ring on the lid of the pump basket. There is a check valve that is on the pressure side of the pump and I changed that as well just in case there was a possible leak. I have turned off the equipment and listened very closely to see if I hear any leaks and I hear nothing. I don't see any air bubbles in the pump basket. With all the equipment turned off, I poured soapy water over all the pipes going and coming from the pump and don't see any air leaks. I am totally perplexed. There is also no water leaking when the pump is running.
I have come back after an hour and the pump is fully primed. It's only dry when I come back the next day. Then the pump is totally dry.
Do you guys have any ideas of what I can try?
Thank you so much for any suggestions. I'm usually pretty good at figuring out my pool problem but this one has me beat.
Note: I have read in some threads here that it would be good to install check valve on the suction side of the pump. However, there is no room in the piping for this.

 

[JamesW]

What is the elevation of the pump to the trough?

Do you have a picture of the equipment?

 

[garin33]

Thank you for your reply James.
The pump sits on a concrete slab that is about 3 inches above ground level. The bottom of the infinity trough is about 4 ft below ground level. The top of the water in the basin is usually about 2 ft below ground level. I will take some picture of the pool equipment when I get off work later today. Note that the pool and trough were installed about 13 years ago and everything has worked fine until last week. Thank you.

 

[JamesW]

Seems like air is getting in somewhere. Check well for a suction side air leak. Also check the pump seal.

 

[garin33]

Thank you James. On the suction side, there is only an Elbow and it goes right into the cement. I did put soapy water on everything and I could not detect any air leaks and when the pump runs, no water leaks. Is there a way to check the pump seal without taking the motor out? The pump appears to run fine and there is no water leaks anywhere around the pump. Thank you.

 

[JamesW]

Do you have a picture of the pump?

 

[garin33]

Here is a picture. Let me know if you need more. It's pretty simple since it brings water from trough to pool and does not go through filter, heater, etc. Thank you.

 

[JamesW]

It seems that the leak has to be from the check valve forward. Check everything again.

 

[garin33]

Thank you James. Ok, I will check again. When you say the check valve forward, do you mean it could be the ball valve with the red handle or the other direction, meaning the pump and couplings? Sorry, if its a dumb question. I'm not a pool expert. I was watching a video last night where they were checking for air leaks and I didn't realize that I am looking for air sucking in. So I guess I'm supposed to see the foamy water being sucked in. I was looking for small bubbles, like on a tire leak. So I will check again. Thank you for your time, these things can be so frustrating.

 

[JamesW]

It might be the pump seal, pump lid, check valve, unions etc.

If you can figure out how to push water into the pump from the trough side, that might help find the leak.

 

[garin33]

Thank you James for all your help. I will try checking again with the suds. Is it correct that I should look for air being sucked in at the leak point?
I will try to see if I can pump water from the trough side. The trough has two drains on the bottom with regular drain lids. So I assume I would remove the drain lids and then force water into the drain holes. Hopefully I can find the air leak by carefully rechecking with the suds. Thank you again.

 

[garin33]

Just an update. When I turn off the pump and everything is really quiet, I can hear a very faint sound of water going through the pipes on the suction side and pressure side. I put my ear to the pipe and I can hear a very quiet sound of water going through the pipe. I tried to isolate it by putting my ear against all the fittings, connections, etc and I can't isolate it. It seems to sound the same no matter what I put my ear against. I very carefully put lots of suds around all the connections, pump lid, check valve, threaded connections, couplers, etc and I see no suds being sucked in or air coming out. The only thing I think it can possibly be is the pump seal or maybe leak in an area underground, which is under the concrete slab. That would be a huge problem of course. In the past (before I put in this new pump and motor about two years ago), I did have a pump seal leak in the infinity pump but it didn't have this priming issue. This is something I have not seen in the 13 years of having the pool, so it's very strange. Any other ideas? Thank you very much for your time. So frustrating. Oh, today after priming the pump and letting it sit for over an hour, the pump basket was still filled with water to the top. So I guess it's a very slow leak. Seems to only go down after sitting over night.

 

[JamesW]

Maybe it's the check valve. Maybe add another check valve after the pump.

It might be an air leak at the ball valve and a leak at the check valve flapper.

I would get rid of the ball valve and put in two new Jandy check valves after the pump.

 

[garin33]

Thank you James. I did replace the check valve and lubed the O ring with Magic lube and also put some lube on the flapper. Is there a reason to have 2 check valves in the same spot? I did put put soap suds around the ball valve and did not see any leaks and note that I never use the ball valve. Last night I ran the pump and this morning I checked the pump and the water was down only about 2 inches in the pump basket so I was able to run the pump without having to fill it with water. So it's a very slow leak. Thank you again.

 

[JamesW]

I suspect that it’s probably on the output side. If it was on the suction side, the pump would have a hard time priming and there would be air in the pump.

I would get rid of the ball valve and put in two new Jandy check valves after the pump.

Two check valves would provide extra protection from a backflow leak.

Maybe redo the unions to make sure that they are not leaking.

 

[garin33]

Thank you James. I will work on it this weekend. I talked to a pool guy that was in the neighborhood and he thought it was pump shaft seal. You mentioned that as well at the beginning. As I said, there is no water that I can see anywhere. Is it possible to have a shaft seal leak but no water leak but it lets in air?
Thank you very much taking the time to help me, much appreciated.

 

[JamesW]

Sometimes you can get a leak on suction vs. pressure or pressure vs. suction.

When the pump is off, there is a negative pressure (suction) that can suck in air when the pump is off if there is a slight crack.

I would get rid of the ball valve and put in two new Jandy check valves after the pump.

Redo the unions to make sure that they are not leaking.

Verify the pump lid seal. Maybe replace the pump lid O-ring. Check the pump lid for cracks.

If the issue persists, then I would change the pump seal.

 

[garin33]

Thanks again for taking the time to help me. Much appreciated. I will try those things this weekend and let you know how it goes. I did replace the pump lid O-ring but have not checked the lid for cracks but will do that as well. Thank you.

 

[garin33]

Hi James, I wanted to give you an update. This weekend, I had my pool guy take a look at the infinity pump plumbing and I told him all the things you mentioned. We were fiddling around with stuff and turning the pump on and off. Like me, he could not detect any leaks, etc. He put a mirror under the pump to see if the shaft seal was leaking even a drop and saw nothing. He turned the ball valve to the off position and turned the pump on for a few seconds. When we turned the ball valve off, we put our ear to the pipe and we did not hear that faint sound of water running through the pipe! So he said to leave it overnight and see what happens. If the pump doesn't lose water in the basket then almost for sure, its the ball valve leaking air. I guess when when we closed the ball valve and then forced water against the ball, the O ring inside seated? Anyway, the next day the water was full in the pump basket! I then turned the ball valve to the open position, ran it for a few minutes and then shut off the pump and checked about 8 hours later and there was still water in the basket! So it appears it is indeed the ball valve as you mentioned and we will take it out of the system. So thank you James for your help!
Out of curiosity, is there any way to have checked the ball valve for air leaks? I put suds all over it and it didn't show any signs of an air leak. It didn't pull any of the suds in or push them out. Did I not check it properly?
Thank you again, super appreciated!

 

[JamesW]

Air is thinner than water. So, you can get air sucked in under suction, but not have a leak under pressure.

Some leaks are difficult to find. I am not a fan of randomly replacing things in general, but sometimes you have to take your best guess at the problem and begin replacing things until the problem goes away.

I would probably put in a second check valve, but it's not critical.