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Pool filter loses prime when shut off - Swimming Pool Help

Pool filter loses prime when shut off

Leaks in the pool, plumbing, filtration system, skimmer, ...

Pool filter loses prime when shut off

Postby dmorgan » Mon 27 Sep, 2010 10:38

I have a 14 year old pool with a hayward super pump and a triton tr-60 sand filter. Pump was new last year with new attachments (impeller etc.) up to the basket housing. I run the filter about 10 hours at night on a timer. I noticed a few weeks ago that the pump was running dry. I do not know how long it ran like that but it could have been a few days. I reprimed it and ran it. I noticed the filter was "sweating water" on the outside of the casing. When I wiped it off, water immediately seeped out. I figured this may also let air in when the filter is shut off so I bought a new triton tr-60 sand filter because the specs on the new one matched the old one and I figured it would match up to the existing plumbing. Well the fittings on the new one were approx 1 inch higher so I had to cut the pipes where necessary to raise the plumbing 1 inch to attach the new filter. I primed the pump and everything ran fine. When I shut the pump off I could hear the filter immediately start to drain water. If I restart the pump within a couple of minutes the pump will prime but there is already alot of air that needs to be bled out of the valve on top of the filter. If I restart is after a couple of minutes the pump has already lost its prime. I have checked for air leaks at all the normal places, I have tried the shaving cream trick on all fittings. I have changed the seals on the backwash valve, jandy valve and pump basket lid. I have looked for water leaks when turning system on and off and listened for any air leaks. When I prime the pump it immediately sucks the water out of the basket housing and when primed it runs at 12 psi. Filter system will run with no problems, no bubbles in pool until I turn it off. Right now I run the system for 2 days straight and turn it off for 2 days, reprime and run again for 2 days etc. I have not been able to get a good explaination on how this system prevents the water from draining out and losing prime when shut off. I need some troubleshooting help if possible to prevent just changing major parts until its fixed. I cannot see any wet spots on the ground that might indicate any inground plumbing leaks. I would appreciate any help or advice that can be offered on how to proceed. Thanks in advance for any help. I can send pictures of system if that would help.
dmorgan
 

Pool filter loses prime when shut off

Postby duraleigh » Mon 27 Sep, 2010 10:53

I primed the pump and everything ran fine. When I shut the pump off I could hear the filter immediately start to drain water.
If your system ran fine with no water leaks and then drains when you shut the pump off, you almost surely have a suction side leak. Somewhere between the pump and the skimmer, air is being drawn into the system.

When the pump is on, that air is manifested by all the bubbles you see in your pump strainer basket which then travel into the filter. When the pump is shut off, that pressurized air forces all the water back towards the skimmer.....that's the sound you hear.

Even after the air in the filter is unpressurized, air continues to leak into the system and, eventually, all the water is drained back into the pool.

The cure is to find that leak. The most common place is the strainer basket lid where the o-ring doesn't seat properly. Next, you could check carefully at all the suction side valves.....they leak frequently. Also check the drain plug(s) at the bottom of the pump strainer basket.

Once you find that leak (or leaks), your system will stay primed.
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Pool filter loses prime when shut off

Postby ChuckGeo » Tue 28 Sep, 2010 18:24

Given that there are no air bubbles returning to the pool from the return line, I'd say that a suction leak is unlikely. I have, on occasion, had air enter the filter through the backwash valve and waste line and eventually cause the pump to loose it's prime. Start with h pump on and operating normally, remove the backwash sight glass from the multiport valve then turn the pump off. If the multiport valve leaks when the pump goes off, you'll hear air hissing when you listen at the sight glass opening. If this is the case, your best bet is to install a cutoff valve on the waste line, after the multiport valve.
Chuck
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25 years leak detection experience
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Pool filter loses prime when shut off

Postby dmorgan486 » Thu 30 Sep, 2010 10:25

I do not think any air is getting in the system while the pump is running. After I get the pump primed I will let it run for serveral days without stopping to make sure the pool stays clean. During this time everything runs fine, I see no bubbles in the return lines and when I open the bleed valve on top of the filter periodically while it is running I do not get any air at all out of it, only water and the system runs at about 12 psi. If I had a suction leak would it make sense that I would be pulling air in that would have to be bled out of the top of the filter? The pump is very hard to prime, if I fill the basket with a hose the water immediately gets sucked into the pump so it seems that the pump is ok but it takes alot of forcing water into the pump with the lid on to get it to prime. I have to pull the hose off of the hayward navigator cleaner, shove a garden hose into the cleaner hose, lift it above pool level to fill the basket with the lid on and it will still take a while for the pump to prime (15-20 mins). I am thinking of pulling the pump and replacing the seals even though I got a new pump with all attachments last year. I do not know how long it ran dry before I noticed the problem since it is on a timer and runs mostly at night. It is possible that it ran dry for 1 week on and off up to 10 hours a day. I am also going to check this weekend if I have any clogs in the suction lines causing reduced water flow. Thanks for the advice and I will update this post after I try a few more things.
dmorgan486
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My Pool: 12,000 gallon play pool, triton tr 60 sand filter, pebble tec surface, hayward super pump

Pool filter loses prime when shut off

Postby duraleigh » Thu 30 Sep, 2010 13:09

If I had a suction leak would it make sense that I would be pulling air in that would have to be bled out of the top of the filter?
Yes.

The quandary is that a pressure side leak (which, when the pump is off, allows the water to drain back to the pool and lets air in) is normally identified by water coming out the pressure side somewhere. In other words, you should have visible water leaking when the pump is on if it's a pressure side leak.
since you don't have visible leaks and it's not sucking in air (pump running) then it is hard to tell which side of the system the leak is.

Perhaps you could locate a wet spot somewhere near your pressure side piping that may help you identify the source. Other than that, I am at a loss other than to say suction side leaks are probably 70-80% of the leaks most folks report.
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Pool filter loses prime when shut off

Postby mas985 » Thu 30 Sep, 2010 19:24

Someone on another forum had a unique situation where the spider gasket was leaking but only when the pump was off. So air entered the filter while the pump was off but when the pump came on, there was no visible leakage. This is also characterized by air coming of the returns but only when the pump is first turned on and after a while no more air comes out of the returns. This sound simliar to your situation.
Mark
Hydraulics 101; Pump and Pool Spreadsheets; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
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Pool filter loses prime when shut off

Postby Pool User » Fri 01 Oct, 2010 09:51

Thanks for the info, I do not know where the spider gasket is, is it part of the jandy valve?
Pool User
 

Pool filter loses prime when shut off

Postby mas985 » Fri 01 Oct, 2010 13:46

Spider gasket is in the backwash valve but it does depend on the type of valve you have, the large round valve. The push pull types don't have this gasket but they do have o-ring seals and less likely to leak.

On the pressure side of the pump when the pressure comes up it can temporarily seal a leak and when the pump is shut off, the air leak opens up and draws in air. These can be one of the hardest leaks to find. One suggestion is after all of the air has been purged from the filter and no more air comes out of the returns, turn off the pump and listen for any air getting sucked into the filter. It might be really hard to hear but you will probably hear the air bubbling up through the filter.
Mark
Hydraulics 101; Pump and Pool Spreadsheets; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
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Pool filter loses prime when shut off

Postby dmorgan486 » Sun 03 Oct, 2010 19:55

Leak is fixed! After running the pump for several days constantly I was able to determine that the ground around all the pool equipment was completely dry so I figured there was no external leak. I tried moving the jandy valve to shut off the pool cleaner and draw water only from the skimmer. When I did this there were bubbles coming from the return lines in the pool. If I moved it off of skimmer only to either a mix of both or floor only, there were no bubbles. But no matter where the valve was set if I turned off the filter pump, the water immediately started draining out of the equipment and within 1 minute the pump needed to be primed again. Even after I would fill the pump basket housing with water the pump was very hard to prime. I decided to do what others suggested and take a hose and run the water all over the pump basket area while I shut off the system after repriming to see what happened. I avoided doing this before because it soaks everything including the ground and I was watching to see if any water leaked out of the equipment which is tough to do when everything is soaked. Well this turned out to be the solution because with the water running over the pump basket housing the sound of water draining out when the pump was shut off went away. When I removed the water flow the sound started and the system started draining. I let it drain and restarted. With the water running over the basket area the pump would self prime and I could bleed the air from the top of the filter. I reduced the area of the water flow to try to isolate exactly where the leak was. If I directed the flow to only the area where the pump attached to the basket housing ,I got the same good result. I decided to try replacing the gasket between the motor and the housing. When I went to the pool store the guy suggested I also replace the pump seal assembly even though the pump was only 1 year old since I was unsure how long it had run dry. I was able to do that myself since I had done it before. So I bought a pump seal and the others came in a kit which included a seal for the pump to the housing, a diffuser seal and a basket lid seal. I had already replaced the lid seal since many said that was a good place to start. I filled the basket with water, put the lid on and turned the pump on and it primed immediately. After all the air was bled from the top of the filter I shut it off. The wonderful sound of silence followed. No water draining. I set the timer to let it run overnight and shut off in the am. Later the next day I went out to manually start it up after being off for half a day and it started right up with no air in system. I should have done the water trick with the hose in the beginning and it would have saved me alot of time. The pool forums definitely helped because most of the very experienced people were adament that an undergounnd plumbing leak was not common and I was about to push myself in that direction and start digging. So I was able to fix the leak with about $37.00 in parts and it took me no more than 1/2 hour to change the necessary seals. I wish to thank all those who took the time to read and respond to this post because I learned alot about my system and it will help me troubleshoot it in the future and maybe be able to help my neighbors save $ by fixing their own systems.
dmorgan486
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My Pool: 12,000 gallon play pool, triton tr 60 sand filter, pebble tec surface, hayward super pump

Pool filter loses prime when shut off

Postby spanishpoolguy » Tue 14 Jun, 2011 06:34

OK, so here's my problem: Pool was working fine until I decided to clean out all of the debris that had settled to the bottom over the winter. Having vacuumed the floor of the pool, (mostly vacuuming to waste, but the last couple of times via the filter) the self-priming pump (Astral Sena,) needs priming every time I switch the system off to clean out the pump filter basket. It typically takes several manual 'charges' before the main filter (Astral Millenium sand filter) shows an increase in pressure and the system starts to work properly. Once the system is shut down, the pump loses its charge, and the water level in the pump basket typically drops to half full. Sometimes with the system running, (but not always,) the main filter pressure gauge fluctuates, accompanied by a 'crackling' noise from the return jets (presumably due to air being expelled?) When this happens, I shut the system down again, ensuring the multiport valve is closed, along with the 3 input pipes to the pump (labelled FONDO, SKIMER and BARREDERO - yes, it's in Spanish!) before charging the pump manually again, repeating the manual charge as necessary until I get a steady pressure indication (typically 12-14psi) and a smooth, crackle-free flow of water from the return jets into the pool. This should be the end of the problem, but - with a steady pressure indication and a smooth flow of water into the pool, accompanied by a pump motor basket full of water, if I switch the sytem off again, it loses half the water from the motor basket (no obvious sign of leakage) and the whole procedure has to be started again! My biggest worry is that I cannot leave the pump to run on a timed cycle when I go away, as it is not priming properly and the pump could run dry, overheat and possibly catch fire! HELP!
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