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Thread: Why would a pressure gauge read 0

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    Why would a pressure gauge read 0

    My pressure gauge was reading 0, so I assumed it was bad. Bought a new one and changed it out and the new one still reads 0. I am getting sufficient return to run my Polaris 165 pressure side cleaner and there is good flow out of the return. When I replaced the gauge I cut the pump off, closed the Multivalve, and shut off the return line - there still was a stream of water that came out the gauge port. Now for background: I have had a persistent air leak on the suction side for a long time. The water in the pump basket always goes down to the intake level as soon as the pump goes on. I have not been able to find the leak. Recently I added a Liquidator and had to close the valve between the skimmer and the pump some to get enough suction. Before installing the LQ my pressure on a clean sand filter was between 8 and 12, after installing the LQ and getting it running properly my pressure went down to 5. Now it has gone to 0. The pool is in good shape and the chemistry is good and as I say I am getting water out of the return, but it bugs me to look at the gauge and see 0. Anybody have any suggestions as to what is going on?
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    Mod Squad Bama Rambler's Avatar
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    Re: Why would a pressure gauge read 0

    Have you checked the impeller to make sure there's not something clogging it up?

    If the impeller is clear then unless the spider gasket is bypassing the sand completely, it should read something. It could be that the gauge port is blocked but you said that water came out of it when you removed it. I'd check that anyway just in case.
    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: Why would a pressure gauge read 0

    Are you getting any water out the backwash line when the filter is in service?
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Re: Why would a pressure gauge read 0

    Quote Originally Posted by stev32k
    Are you getting any water out the backwash line when the filter is in service?
    No. And I can backwash successfully.
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    Re: Why would a pressure gauge read 0

    Mine reads 0 when pump is on low, but 10 when it's on high... not hijacking, but posting so I can follow the answers to this!! Pool store guy was not concerned when I told him it was 0 on low. *shrug*
    Vogue Vectra 30' Round (21,200 gallons), Waterway 2HP 2-speed, 27" sand filter - TF100 -- Southern IL - Install 06/2012
    Last minute upgrade from 27' due to error in dealer inventory *yikes*

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    stev32k's Avatar
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    Re: Why would a pressure gauge read 0

    That sure sounds like a bad spider gasket to me. I have to replace mine about every 5 years. It's also possible, but less likely the inlet pipe in the middle of the filter is broken or cracked that would also allow bypassing the sand. Have you seen any sand in the pool?
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Re: Why would a pressure gauge read 0

    I have not seen any sand in the pool. I just checked the impeller and do not feel anything in there. I can turn it from the basket with a screwdriver. It does not real easy, but is smooth. I have removed the multivalve head and the spider gasket looks good. I also back-flushed from the filter to the pump with a hose and only water came out, so I am thinking there is no obstruction, but I think I will remove the hose from the top of the pump and flush from there. I can't remember, should I put gasket lube on the spider gasket when I put it back together? Any other ideas?
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    stev32k's Avatar
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    Re: Why would a pressure gauge read 0

    Did you look at the valve stem, spring and O-rings? You should put o-ring lube on the gasket and the o-rings. When the pump is running can you remove the pressure gauge to see if anything comes out? Look at the pressure gauge inlet to make sure it is open and not covered with teflon tape or something. When you take the gauge out see if you make it move with a water hose. You should be able to see some pressure just by holding a water hose to the inlet and wrap your hand around it - you'll get wet, but the needle should show a pound or two of pressure.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Re: Why would a pressure gauge read 0

    OK, I have flushed the impeller and no debris came out. I have put it all back together using pool lube on all gaskets and now I am running the system with the suction side valve fully open and the LQ is flowing the same as it was before when the valve had to be partially closed. The pressure gauge went up to 1 from 0. I guess that is progress.
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    Re: Why would a pressure gauge read 0

    Is the pump strainer basket devoid of all air?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Why would a pressure gauge read 0

    I did visually inspect the spring and O ring as well as the spider gasket. All look good to me. So I lubed the gasket and o ring and put it back together. I visually inspected the gauge port and it is clear of any obstruction. I did not try to run it without the gauge installed, but earlier when I removed the gauge with the pump off a stream of water came out the port.
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    Re: Why would a pressure gauge read 0

    No, there is air in the basket. I fill it up with water and then when I turn on the pump the strainer basket quickly sucks air until the water goes down to the top of the inlet to the basket. This has been an ongoing problem. I have tried to find a suction side leak, but as of yet to no avail. I didn't think that was the problem because for months I have had this air leak and still showed pressure on the gauge.
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    Re: Why would a pressure gauge read 0

    Does your pump make any different or unusual noise when it's running? Can you see any air in the liquidator line going to the pump, or is there air getting in the pump strainer basket?

    Edit: sorry I didn't see the question had already been asked.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Re: Why would a pressure gauge read 0

    Is your pump located below the water level of the pool?
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Re: Why would a pressure gauge read 0

    Your gauge reads zero because of the suction leak. Find that leak, your basket will fill with water and your gauge will be normal....probably higher than five.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Why would a pressure gauge read 0

    Yes my pump is below the water level. OK Dave I will keep looking for the air leak.
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    stev32k's Avatar
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    Re: Why would a pressure gauge read 0

    Something about your setup I don't understand. Normally, if the water level in the pool is above the pump suction a suction side leak should draw down the pool level before it drains the pump when the pump is off. What is keeping that from happening?
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Re: Why would a pressure gauge read 0

    Quote Originally Posted by stev32k
    Something about your setup I don't understand. Normally, if the water level in the pool is above the pump suction a suction side leak should draw down the pool level before it drains the pump when the pump is off. What is keeping that from happening?
    Good question. The suction side does not leak when the pump is off. The plumbing is pvc and includes two unions and a ball valve. My guess now is that there is a small leak that at one of these joints that only shows up when the pump creates a suction. I am wondering if taking the unions apart and lubricating the gaskets inside will stop the leak? What is the best way to check for a leak in a union or ball valve?
    Larry in Texas

    Above ground 7,700 gallons, 19 inch sand filter ( 2 sq. ft.), Liquidator, and a WaterWay Hi-Flo Pump with an A.O. Smith 1 hp SF 1.0 motor.

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    stev32k's Avatar
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    Re: Why would a pressure gauge read 0

    If you only have one suction intake on the skimmer I would get an expansible drain jet - they are called different things by different mfg's but they are a rubber bulb connected to a water hose that expands under pressure to seal and pressurize a pipe. Close the suction valve to the pump, put the drain jet in the skimmer intake, turn on the water to pressurize the line and look for the leak. You can buy them at Lowes or Home Depot. If you have more than one suction point like a bottom drain plug one and test the other.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Mod Squad Bama Rambler's Avatar
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    Re: Why would a pressure gauge read 0

    Running water over the fittings while the pump is running and observing the pump basket is ususally the best way to tell where a leak is.
    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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