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Thread: No/low pressure cycling problem. Any ideas?

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    deanchat's Avatar
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    No/low pressure cycling problem. Any ideas?

    No-low pressure cycling. Pump basket will fill (with water) and then, whoosh, drops down about half or more. Feeling the outlet jets I feel no pressure and then a short burst (not full pressure) that seems to correspond with what I observe at the pump basket. This cycle takes about 5 seconds and continues over and over. No bubbles coming out of the returns.

    Yesterday I vacuumed the pool and sucked up a bunch of leaves. The problem occurred after vacuuming. The number of leaves in the pump basket seemed to be less than the number I vacuumed up. Can they be stuck in the suction-side plumbing somewhere? Would that cause the problem I am having? How does one clear stuff out of the plumbing?

    Thanks,
    Dean

    PS I keep the pool open during the winter and run the pump anytime it looks like we will have freezing temps. Pump has been working fine recently, even running 24/7 during a recent cold spell.
    37x16 IG vinyl, about 20K gals
    Pentair FNS 60 DE filter
    3/4 hp Pentair Challenger pump
    1 skimmer, 2 bottom returns + 1 step jet
    AutoPilot Dig 220

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    Re: No/low pressure cycling problem. Any ideas?

    Welcome to TFP!!

    The pump is starving for water. Either the water level is too low, the weir (skimmer door is stuck closed) or there is an obstruction in the line (like leaves). Is the skimmer your only suction port? if not, can you try running the pump with the skimmer closed and any other suction ports open?

    If the line is obstructed, try forcing water or air backwards through the line (from the pump to the skimmer). I can give a couple ideas on doing this, but check the water level and the weir first.
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    Re: No/low pressure cycling problem. Any ideas?

    The symptoms you mention sound exactly like low water level where the skimmer can't fill quick enough and is sucking in some air, then as the pump stalls, the skimmer refills and reprimes the pump. Alternatively, I've seen this if the lid on the pump basket is not properly seated. It might look seated but could still be allowing air in.

    A water level drop in the pump basket must mean air is getting into the line. If the line is blocked, it would restrict flow, but the water level in the pump basket should remain constant - the same as if you shut off a valve. The air may be getting trapped in the filter and not have a chance to get out to the return lines yet, or it is such a little amount that it gets blended with the water and you won't notice big bubbles coming out of the returns.

    By the way, why are you not vacuuming through the skimmer and collecting the leaves in the skimmer basket as opposed to the pump basket? The pump basket should not be used as a primary source of collecting debris.
    25' x 13' Roman, 12000 gal IGP, Plaster, with 500 gal Spa
    SWG, 1 HP Max Flo Pump, C-900 cartridge filter
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    deanchat's Avatar
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    Re: No/low pressure cycling problem. Any ideas?

    Thanks for the input. The water level is good (a little high if anything) and the weir looks good too. I tried a drain cleaning bladder ("water weenie" I have seen some people call it) at the skimmer end. At the pump basket end the right angle makes it impossible to but the bladder in far enough. I tried a 3/8" plumbers snake at both ends but it doesn't get very far (a couple of feet) before it seems to jam up on a tight turn or something.

    The skimmer is my only water inlet, so unfortunately I can't bypass it.

    The pump basket top seals well and I always put it on pretty snugly. If it is not a suction-side plumbing obstruction, could it be an issue with the multi-port (gasket)? When I shut the pump off I notice a lot of gurgling going on, for at least 30 seconds or so. Sounds like it is coming from the filter. I don't believe this is how it has acted in the past.

    I filter with the hose directly attached to the bottom of the skimmer. My skimmer basket has a handle that prevents it from being used during vacuuming (won't allow one of those disc-seal things to be used). Haven't had a problem with doing it this way before, I usually check the pump basket once or twice while vacuuming to make sure everything is okay. Maybe it's time for a new approach.

    Thanks,
    Dean
    37x16 IG vinyl, about 20K gals
    Pentair FNS 60 DE filter
    3/4 hp Pentair Challenger pump
    1 skimmer, 2 bottom returns + 1 step jet
    AutoPilot Dig 220

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    Re: No/low pressure cycling problem. Any ideas?

    OK, the snake isn't working and you can't get the 'water weenie' (I assume it's like the drain king) into the d*mn input pipe at the pump. If you have good water pressure in your garden hose, wet a rag and wrap it around the hose ~ 3" from the end - the wet rag will help you ~seal the in port on the pump. Alternately, you can use a shop-vac on blow to try and clear the line.

    If it's what it certainly appears to be, a leaf clog has settled into one of the elbows in the skimmer line and the best way to get it to dislodge is to force it backwards through the pipe! It helps to have 2 people doing this, one to apply backwards pressure from the pump and the other to see if anything's coming out Also,, with 2 people, the one poolside can cap the skimmer port while pressure is being applied and release it to really put a 'slug' of pressure on the obstruction.

    I'll further assume that you don't have unions, which would allow you to get the pump out of the way. What sort of multiport do you have on the filter? You might be able to put it on 'waste' and apply the 'water weenie' to that

    Please try what I've said. If it still doesn't work, others here may have a trick or 2 to share and i have a couple ideas on a 'last ditch attempt' to clear this. Keep us informed, please
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    Mod Squad zea3's Avatar
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    Re: No/low pressure cycling problem. Any ideas?

    Get yourself an in-line leaf catcher to use when you vacuum. I have one from Zodiac and I use it with both my manual and my automatic vacuums. Saves me a lot of hassle!
    TFP Moderator
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    deanchat's Avatar
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    Re: No/low pressure cycling problem. Any ideas?

    Thanks, I'l try to get some pressure on the skimmer line in the reverse direction and see what happens. I tried the water weenie (drain king) at the pump basket end even though I couldn't get the bladder all the way in. Yup, it burst as expected (I kept my distance assuming that would happen).

    Not sure what unions are, so I probably don't have them. The pool is about 15-17 years old, I have owned the home for about 2.5 years so there is a lot of "hmm, what's that" and "hmmm, why is that pipe capped off" going on.

    I have a Pentair SM-10 multiport with filter, recirc, waste, closed, rinse, backwash and probably something else I am forgetting.

    That Zodiac leaf filter thing looks pretty cool. I've never had a problem like this before, and I have vacuumed up leaves like this several times before. I bet some of the leaves had some twigs still attached or something. More recently I have been letting my Pool Rover Plus take care of leaves and stuff, but I thought a quick vacuuming of the leaves would be quicker. Should have used the d*mn Rover!

    Thanks!
    Dean
    37x16 IG vinyl, about 20K gals
    Pentair FNS 60 DE filter
    3/4 hp Pentair Challenger pump
    1 skimmer, 2 bottom returns + 1 step jet
    AutoPilot Dig 220

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    Re: No/low pressure cycling problem. Any ideas?

    Dean, it's been a couple weeks and I'm hoping that you've been able to solve the problem

    If you are handy with a digital camera and can use Photobucket or similar, post some pics of the lines/ equipment you aren't sure about - we'll help ya!
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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