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Thread: Real Stumper: Too much skimmer suction?

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    jewettg's Avatar
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    Real Stumper: Too much skimmer suction?

    I can not figure it out. Our pool has developed a very interesting problem. Basically everything seems to be functioning OK, except one skimmer is pulling to much water and empties before it can refill, thus the pump starts to suck air and loses prime. Bizarre.

    Some pool make-up: Pentair pumps, filters, and parts. 15,000 gallon pool with a spa. Everything is controlled by a central electronic control system. There are two pumps, one for the normal filter operation, the other for a waterfall effect from the spa into the pool. There is a pool heater, chlorinator, and a filter. I also have a pump for our cleaner ("rover"). Each skimmer has its own valve, along with the main pool drain, separated by a motorized valve that separates the spa main drain. A little diagram below: <> = manual valve. <M> = motorized valve.

    Code:
    
      +-----+-----+-----<M>----+
      |     |     |            |
     <>     <>    <>           |
      |     |     |            |
     SKM   SKM   Main         SPA
      1     2    Drn          Drn
    
    FullSizeRender.jpg

    The spa part does not seem to be involved, but will explain it just in case. There are two drains on the bottom of the main pool. One goes to the normal filter operations, the other feeds the second pump that pumps directly into the spa to create the waterfall effect from the spa into the pool. There is a valve that extends the spa into the main filtration system or causes the spa to loop back into itself.

    The filter has a pressure valve on it and it hovers at 19 or 20, so this is good. When there a loss of prime or the pump is suck area, the pressure in the filter drops and you can see the needle bounce!

    All pumps and valves seem to working, so I can not find any obvious equipment faults, but please let me know if I am off base.

    So here is the problem:

    If the all manual valves are open, drawing water from both skimmers and main pool drain the pump will soon lose prime. Looking at skimmer 2, it will literally have no water in, all be sucked down until the pump loses prime and stops pumping, and only then does it refill with water from the pool.
    If I close skimmer #2 valve, the pump will prime again and everything starts working. I have isolated each skimmer, including the main pool drain, and the spa drain (there is a switch on the motorized valve that you can operate to have it turn), and as long as skimmer #2 is off, everything works.

    Also note: even with all three valves on, skimmer #2 still empties out and sucks area causing the pump to lose prime. Ugh!

    I did some searching online and can not find anything that matches this problem. I watched the video about a possible clog, but that does not make sense since the skimmer basically has too much suction, not too little as a clog my prescribe. I even tried throwing the hose into the skimmer #2 and even with the extra water input, the skimmer empties out and the pump looses prime.

    I have checked for leaks in the pipes coming from skimmer #2, but I can not find any.

    HELP? Any other troubleshooting I can try?

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    Mod Squad pooldv's Avatar
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    Re: Real Stumper: Too much skimmer suction?

    Welcome to TFP!

    Sounds like the weir might be stuck. That is the flapper door. Make sure it is flappy.
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    Re: Real Stumper: Too much skimmer suction?

    Quote Originally Posted by pooldv View Post
    Sounds like the weir might be stuck. That is the flapper door. Make sure it is flappy.
    Can you help me understand what you mean? The flapper on the actual skimmer is working just fine. It is down, allowing all the water that could possibly come from the pool into the skimmer.

    The only other "flappers" that might be present are in the pumping station that control back-flow (since the spa sits above the pool), to keep the spa from losing water when the pump shuts off. However, those seem to be working as well. They open when the pump is on and close when the pump is off.

    Any other ideas?

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    Re: Real Stumper: Too much skimmer suction?

    Have you tried just opening skimmer 2 valve just a bit and slowly increasing untill it works correctly (it's balancing as in any heating system)
    10,000 gallons inground Leisure fibreglass pool, Hayward powerline pump, Quality120 glass media filter, 27kw output air source heat pump and thermal cover.
    Retractable cover with Polycarbonate roof and glass side for all year round use. K-2006C test kit and Speed stir

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    Re: Real Stumper: Too much skimmer suction?

    Quote Originally Posted by denniswiseman View Post
    Have you tried just opening skimmer 2 valve just a bit and slowly increasing untill it works correctly (it's balancing as in any heating system)
    Thank you Dennis! Yeah, I did try that to purge any air in the line that might be causing causing a flow problem. Basically what happened was, when I turned the valve on slightly, no issues, there was just enough suction to pull water in, not causing an issue. However, opening it more than a 1/4-open or 1/3-open, the skimmer empties, causing the air to be sucked in. If I turn it back, normal suction returns, no air. I tried moving it back and forth slowly as described on the videos on YouTube, with no luck.

    Funny thing.. it is ONLY this skimmer. There is no water loss in the pool. It is a closed system. Arrghh.

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    Re: Real Stumper: Too much skimmer suction?

    Anytime air is being sucked into the skimmer, the question of pool water depth comes up. Is your pool water level up to about 1/2 the height of the skimmer mouth?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Real Stumper: Too much skimmer suction?

    Quote Originally Posted by duraleigh View Post
    Anytime air is being sucked into the skimmer, the question of pool water depth comes up. Is your pool water level up to about 1/2 the height of the skimmer mouth?
    Thank you Dave. Yes, the pool water level is perfect. It is only affecting one skimmer, if I eliminate that skimmer (using the manual valve), the pool operates perfectly. No issues.

    Just for giggles, I am adding more water to the pool than I usually do. We have had this pool for 11 years and have always added water to "1/2 up the tile", which equates to minimum of 1/2 the skimmer height. I will make sure to keep the water level away from the top of the skimmer so it will actually "skim" (the flapper works). We have in the past had to empty the pool when it rains too much, but always try to keep the pool level "1/2 up the tile".
    My Pool: 15K gallon pool, with spa that has waterfall effect that spills into pool. Pentair equipment (pumps, filter, heater, etc..). Spa heater (could be used to heat pool), two pumps (1 for normal filtration, 1 for waterfall effect). Pump for cleaner. Automatic chlorinator. DE filtration system.

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    Re: Real Stumper: Too much skimmer suction?

    What size is the main pump? It looks pretty new???? what size is your suction side plumbing?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Real Stumper: Too much skimmer suction?

    Quote Originally Posted by duraleigh View Post
    What size is the main pump? It looks pretty new???? what size is your suction side plumbing?
    Everything is 11 years old. We have replaced parts on our cleaner, fixed the motorized valves, and done general maintenance, but those pumps are original equipment.

    Pump Info:
    Pentair WhisperFlo
    High performance pump

    Pump Info.jpg

    Looking at the picture I posted, in is basically in the middle. The far right side is the waterfall pump, the left (beige pump) is the filtration pump.
    My Pool: 15K gallon pool, with spa that has waterfall effect that spills into pool. Pentair equipment (pumps, filter, heater, etc..). Spa heater (could be used to heat pool), two pumps (1 for normal filtration, 1 for waterfall effect). Pump for cleaner. Automatic chlorinator. DE filtration system.

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    Mod Squad pooldv's Avatar
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    Re: Real Stumper: Too much skimmer suction?

    Quote Originally Posted by jewettg View Post
    Can you help me understand what you mean? The flapper on the actual skimmer is working just fine. It is down, allowing all the water that could possibly come from the pool into the skimmer.
    Yes, the weir door between the pool and the skimmer is what I mean. Sometimes debris can get wedged between the weir and the side so it can't move freely. So, water is flowing in from the pool the whole time but the skimmer well is empty? Maybe there is a clog in the line of skimmer #1 causing it not to flow enough water. What happens if only skimmer #1 is open? Has there been a lot of debris in the pool recently that could have caused a clog somewhere in the plumbing?
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    Re: Real Stumper: Too much skimmer suction?

    Just a quick update!

    I have finished adding water to the pool, that "Dave S." hinted at. I thought - why not. When I turned on the pump, I had left skimmer #2 closed so as to make sure the everything was running ok. I then opened skimmer #2 valve 50%, and a ton of air poured in, but then leveled out. I waited and it remained ok. I turned it a bit more towards open, and it still was OK, and then turned 100% open, and waited. The pump started to suck air, and lost prime. I went over to the skimmer, and water was pouring, but being pumped out faster.

    ...and now the embarrassing part!

    Just to ensure everything I stated above was true, I put my swim trunks on and jumped into the pool. I went over to the skimmer in question and found that the flapper was indeed working, but noticed something was prevent the water from coming in fully. I reached in and felt around and found a piece of clear plastic wrap that was acting as a bridge preventing water from getting in. I could not see the plastic when I was inspecting it from the top (ground), and only found it after feeling around.

    Once the plastic was removed, the skimmer was working perfectly. Apparently the plastic wrap was just enough of a barrier to block just enough water, fool me because the flapper was working. The pump is working 100%, all skimmers are operational, no lose of prime!

    I guess it just takes talking to some pretty smart and pool saavy people to just question what you have already done.

    My Pool: 15K gallon pool, with spa that has waterfall effect that spills into pool. Pentair equipment (pumps, filter, heater, etc..). Spa heater (could be used to heat pool), two pumps (1 for normal filtration, 1 for waterfall effect). Pump for cleaner. Automatic chlorinator. DE filtration system.

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    Mod Squad pooldv's Avatar
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    Re: Real Stumper: Too much skimmer suction?

    Hooray for cheap and easy pool repairs!
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Real Stumper: Too much skimmer suction?

    Cha-ching!!! BTW, that is an awfully strong pump for your size pool. If you ever change it out, a 1.5 HP -2 speed or even a 1 hp 2 speed would save you a LOT on electricity and just may pay you back in just a few years.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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