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Thread: Cause of Pump Basket Not Filling 100%

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    Cause of Pump Basket Not Filling 100%

    I've had a Jandy Stealth 2.5 HP pump for about 8 years, which is rarely used (used for spa jets only, no recirculation/etc -- about 10 hours a month usage).

    Recently, I noticed the output decreased significantly, and there seems to be a little air coming out along with the water from the jets.

    I went to the pump and noticed that it's not filling the basket completely. In the past, it worked just like any other pump. That is to say that once it was primed, the basket was filled full as it pumped.

    It's not making any odd noises, it does not sound like it's laboring or having any issues with the pump or motor. I thought it might be getting air somehow, but if it were, it would be difficult to locate as the pipes are entirely underground, start-to-end (excluding the last 2' into the pump).

    Does anyone have any ideas what would be the most common reason for this, or how I should begin to diagnose?

    Thank you in advance
    RKM
    15,000 gal/16x32 Doughboy expandable vinyl liner pool, w/deep end
    Hayward Pro Series high rate sand filter/Powerflow Matrix 1.5 hp pump

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    Mod Squad zea3's Avatar
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    Re: Cause of Pump Basket Not Filling 100%

    How high is the water level in your skimmer? If it is less than 1/2 way up the skimmer it could be sucking in air at the skimmer. Also make sure the pump basket and the filter are clean. A really dirty filter can reduce flow and cause you to lose prime. Make sure the pump basket lid is getting a good seal by putting silicon pool lube on the lid o-ring. Check that the drain plug on the pump is snug. Other wise check the exposed pipe for air leaks, especially where 2 pipes are joined. With the pump running slowly trickle water over the joints and watch for water to be sucked into the pipe.
    TFP Moderator
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    Re: Cause of Pump Basket Not Filling 100%

    +1 what zea said.

    If the basket is not full, air is getting in somewhere. Sometimes it can be a blockage in the suction line wherein the pump can't get enough water so it pulls air from a seal that normally it would not. More often, it is simply a seal (valve, plug, etc.) that, over time, simply lets in air where it didn't before.

    While the leak is often hard to find, the good news is that a broken underground pipe is ALMOST never the cause.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Cause of Pump Basket Not Filling 100%

    Zea & Dave,
    Thank you for the great information! Fortunately I work from home so I was able to follow-up on your suggestions.

    The waterline is at the top of the skimmer. It's run good in the past when it's much lower, so I'll move on to the next item. The pump basket is very clean, but to be sure, I cleaned/re-seated the O-ring and cleaned the pump basket. Next, I tried your suggestion to monitor suction at the pump, but there was nothing. The drain plug was also snug, and no bubbling when I splashed water onto it.

    After everything I've tested, I'm leaning towards Duraleigh's additional suggestion, that something may have become stuck in the line causing it to suck air from somewhere that would normally not be a leak. Unless there may be something else I haven't tested, for example, could it be related to a seal going bad on the impeller or anything along those lines?

    Thank you again for the insight!
    15,000 gal/16x32 Doughboy expandable vinyl liner pool, w/deep end
    Hayward Pro Series high rate sand filter/Powerflow Matrix 1.5 hp pump

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    Re: Cause of Pump Basket Not Filling 100%

    I am inclined to suspect either the impeller has debris caught in it or the suction side union's O-ring is out of position.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    Smykowski's Avatar
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    Re: Cause of Pump Basket Not Filling 100%

    Quote Originally Posted by PoolGuyNJ
    I am inclined to suspect either the impeller has debris caught in it or the suction side union's O-ring is out of position.

    Scott
    See this thread, maybe it will help....poor-suction-problem-t38850.html
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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