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Thread: Pump losing prime when turned off and air sucking sound

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    Pump losing prime when turned off and air sucking sound

    I have a sand filter like the one I have attached a picture of. Over the last few weeks the pump has not been sucking as strong as it used to and the pump basket has had a lot of air in it. I have not seen any water leaks but the water drains out of all the pipes and salt water generator when the pump turns off. Tonight I was standing near the pump when it turned off and I heard a sucking sound like air was being sucked in somewhere from the white valve on top of the sand filter somewhere near the handle. Are there user replaceable washers or seals in the filter that I could replace myself or do I need a professional.
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    15.8K gallons (60K Litres), IG, pebble, Davey 1hp 300lpm, sand filter, K Chlor SWG, Kreepy Krauly.

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    Mod Squad JohnT's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    Most likely you won't see a water leak, because your leak is on the suction side of the pump where the water is under a little bit of negative pressure. A leak there results in air entering the system causing bubbles in the strainer basket. Your leak is between the skimmer(s)/drain(s) and the impeller of the pump.

    The most common problem is the O-ring on the basket lid itself. Check the condition of the O-ring and lubricate it with pool lube and make sure the lid is tight. Next do the same think with the drain plug on the pump basket. If those aren't the problem, check any fittings or partiucularly valves near the inlet of the pump.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Pump losing prime when turned off and air sucking sound

    The pump is only a few months old and the seals on the strainer basket are all perfect and in fact still have some of the lubricant from the initial install on them. This problem has only started in the last few weeks which make me think a seal on the sand filter is leaking and that is where the sucking sound can be heard when the pump turns off. I will maybe undo the bolts on the sand filter and have a look to see if anything looks worn.
    15.8K gallons (60K Litres), IG, pebble, Davey 1hp 300lpm, sand filter, K Chlor SWG, Kreepy Krauly.

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    Mod Squad JohnT's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    Quote Originally Posted by aussieorchid
    The pump is only a few months old and the seals on the strainer basket are all perfect and in fact still have some of the lubricant from the initial install on them. This problem has only started in the last few weeks which make me think a seal on the sand filter is leaking and that is where the sucking sound can be heard when the pump turns off. I will maybe undo the bolts on the sand filter and have a look to see if anything looks worn.
    A leak after the pump will not cause this. Water leaks out when the leak is after the pump and air leaks in when the leak is before the pump. 100% certain it is in or before the pump and 100% certain it isn't a problem in the filter.

    The reason you hear the air in the filter when the pump is off is that the air leak on the other side of the pump is letting the water drain out of the filter.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Pump losing prime when turned off and air sucking sound

    I know what you are saying is right but for the life of me I can not see where there can be a leak before the pump. I will have to check all the connections again tomorrow morning but there is only one pipe from the skimmer basket at the pool to the pump and then one connection from the pump to the sand filter which is again after the pump. Maybe I will also relub the pump basket lid as that is the most obvious place for the leak and the pump inlet pipe connection.
    15.8K gallons (60K Litres), IG, pebble, Davey 1hp 300lpm, sand filter, K Chlor SWG, Kreepy Krauly.

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    Mod Squad JohnT's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    The basket lid needs to be pretty tight. You can try pushing on it or tightening it while the pump is running. You can run the water from a hose over a valve while the pump is running and when you hit the leak the bubbles in the basket will stop.

    Look carefully for a small leak when the pump is off or a small spurt of water right as the pump shuts off. Those are common with an air leak.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Pump losing prime when turned off and air sucking sound

    Just chiming in to reinforce what JohnT is saying.....the leak is on the suction side of the system.....100% certain.

    There is a drain plug(s) on the bottom of the pump strainer basket.....are those tight? Is the water high enough in your pool so that it is not sucking air through the skimmer(s)?

    The leak at the filter needs to be fixed as well, but that's not the source of air.

    If the filter leak is coming from the handle area, it may be as simple as re-seating the handle. If you do not fix both leaks(filter and suction side), you will lose prime each time you turn off the pump.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Pump losing prime when turned off and air sucking sound

    Try using shaving cream on all the possible leaks; joints, valves, unions, lids etc. Apply with the pump off, then watch for areas that such inward when you turn the pump on.

    Sent via Tapatalk...
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
    13500 gal, Vinyl Liner, Fiberglass Slide, TF-100 Test Kit, Hayward 210T
    sand filter, A.O. Smith 1.5HP main pump motor (C48L2N134C1),
    Hayward SuperPump (model ?), Polaris 380 & PB4 Booster Pump

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    Re: Pump losing prime when turned off and air sucking sound

    Is the pressure on your filter higher than normal? Have you backwashed the filter?

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    Re: Pump losing prime when turned off and air sucking sound

    Hmm. I thought it was possible for the filter and plumbing to drain with the pump off due to an air leak on the pressure side (top of filter for example) that may not actually leak much if any water when the pump was on. That was my first thought especially if no air it's seen in the pump basket after everything is primed and the air is repressed from the filter.

    EDIT: Disregard ... I missed the info about air in the pump basket

    Posted from my Droid with Tapatalk ... sorry if my response is short
    Jason, TFP Moderator
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    Mod Squad Bama Rambler's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    Quote Originally Posted by aussieorchid
    ... and the pump basket has had a lot of air in it.
    This makes me agree that it's a suction side leak. The sound you hear when you shut down the pump is the air that's gotten into the filter is pushing the water back out of the plumbing as it's depressurizing.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: Pump losing prime when turned off and air sucking sound

    Well I pulled the sand filter apart and greased all the seals. This has almost fixed the pump loosing its prime when off it still has a slow leak so maybe some new seals are needed. I have still not been able to fix the pump sucking air into the filter basket. Although I am not sure it is sucking air but more like not sucking enough when the Kreepy Krauly in attached. When the Kreepy is not attached it seems to be fine. I ahve checked the vacuum hose for leaks as well and found none. I did a bit of web searching and saw mention of the main drain needing to be plugged. I presume I have a main drain as I have a blue circular plate fitted at the middle of the deepest part of the pool and when I purchased the house the Kreepy was already installed and running. The water level was a little low last week and I noticed water was coming into the skimmer box from the two holes on either side of the skimmer box just above where the vacuum plate sits and for the life of me I can not remember water ever flowing out of them in the 5yrs I have been here. Is it possible a problem with the main drain being unplugged or a plug coming out could cause this. I will have to get into the pool when it is light again and see if I can see anything or feel any suction at the main drain. May be time to call in the pool service guy if that is my problem.
    15.8K gallons (60K Litres), IG, pebble, Davey 1hp 300lpm, sand filter, K Chlor SWG, Kreepy Krauly.

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    Mod Squad Bama Rambler's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    If it's not sucking air into the pump basket when the vacuum isn't hooked up, then the added suction head (vacuum) is opening up a leak that is normally sealed under normal suction. That's a pretty common thing to happen. It's usually the pump basket lid or the drain plug that's leaking. Clean and lube the lid o-ring and remove, clean and reseal the drain plug. Also check around any valves you may have.

    As for the water coming into the skimmer from the side ports, a pic of it would help but I suspect that it's an equalizer line and it's there for such instances where the water level gets low so the skimmer doesn't suck in air.

    Keep looking for that air leak and you'll find it. It only requires a very small leak to let in a lot of air.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: Pump losing prime when turned off and air sucking sound

    Quote Originally Posted by UnderWaterVanya
    Try using shaving cream on all the possible leaks; joints, valves, unions, lids etc. Apply with the pump off, then watch for areas that such inward when you turn the pump on.
    Did you try this yet?
    Another option is to wrap electrical tape around any joint you have - if this reduces the amount of air in the pump basket then you know you have found the source (or one of the sources).
    As for the vac hose - take it under water filled with air one section at a time looking for bubbles. Even if it isn't sectional the idea is to move the trapped air along the tube checking all areas.
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
    13500 gal, Vinyl Liner, Fiberglass Slide, TF-100 Test Kit, Hayward 210T
    sand filter, A.O. Smith 1.5HP main pump motor (C48L2N134C1),
    Hayward SuperPump (model ?), Polaris 380 & PB4 Booster Pump

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    Re: Pump losing prime when turned off and air sucking sound

    I tried the shaving cream on all joints and nothing could be seen. I have added a pic of the skimmer and what I assume is the main drain cover. The skimmer has one hole in the bottom that sucks to the pump and one hole either side higher up in the skimmer. Both have a black thread just inside the holes. I also have a circular cover in the bottom of the pool sorry the pic is not great the pool is a little cloudy and it is very sunny outside. Would I be able to plug the two holes in the skimmer or does the plug have to go into the bottom of the pool. One of the holes is from an inlet in the pool wall about 500mm from the top of the pool edge I assume to provide water to the skimmer if the pool level gets very low and the other I assume is the main drain one.
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    15.8K gallons (60K Litres), IG, pebble, Davey 1hp 300lpm, sand filter, K Chlor SWG, Kreepy Krauly.

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    Mod Squad Bama Rambler's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    I think you're correct in your assumption. The bottom port is for the pump and the port in the side closest to the pool should be the equalizer (inlet in the pool wall) and the other should be the main drain. If the vacuum plate sits in the skimmer below the side ports, as it appears to, there's no use in plugging either port.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Pump losing prime when turned off and air sucking sound

    Well the saga continues. I replaced the spider gasket today as it did need replacing anyway. That has fixed the pump losing its prime but not fixed the pump not sucking properly as was to be expected. I was having a chat to the pool shop about the issue he has given me two more things to check. Firstly when the pump is running without the Kreepy vacuum all is fine which makes the pool shop guy think it is not a leak in the pipe work but either the Kreepy or the pump seal when it is under load.

    He suggested to
    1) check the kreepy hose I did replace the hose not that long ago with a new one the last owner had left here. They said it was a genuine hose but when I installed it the hose just looked a fraction smaller in diameter than the old one. I am going to grab a friends tomorrow and see if that helps I forgot to take a piece to the shop to compare today.

    2) Possibly a mechanical seal in the pump has gone. As the pump is under warranty he said if that is my issue he will replace that free as they are the service agent.

    So I have moved forward slightly who says owing a pool is great.
    15.8K gallons (60K Litres), IG, pebble, Davey 1hp 300lpm, sand filter, K Chlor SWG, Kreepy Krauly.

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    Mod Squad Bama Rambler's Avatar
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    Re: Pump losing prime when turned off and air sucking sound

    Of all the suction leaks we seen here I don't ever remember anyone attributing one to the shaft seal. Not saying it can't happen, just we've never heard of it. Usually when the shaft seal is the problem it will leak water when the pump is running.

    Once you get past these few hurdles and get comfortable with your pool it will be much more enjoyable. I promise!
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Pump losing prime when turned off and air sucking sound

    I've had this problem twice. First time it was the spider gasket. I replaced the entire top of the filter, since my gasket was molded in.

    Second time it was the 3 inch "O" rings on either side of the SWG cylinder. I replaced them and lubed them for the first time.
    19k gal, STS1072R A.O. Smith C-Face Motor .75HP Full-Rated 2-Speed, Hayward Sand Filter

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    Re: Pump losing prime when turned off and air sucking sound

    Air getting into the pump when the pump is running does not come from the pressure side of the system......air comes from the suction side only.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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