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Thread: Anyone know recommended GPM flow for skimmer in 100% position?

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    Anyone know recommended GPM flow for skimmer in 100% position?

    I seem to have a slow skimmer. I dont see a lot of flow into it. Adjusted the jets to help "push" debris floating into the skimmer, but I'm trying to figure out if the restriction is causing problems or not. Looks like a "blob" of concrete in the bottom pipe of the skimmer where it attaches to the pipe going back to the pump is partially blocking. Want to figure out if its worth the trouble to clear it out somehow.

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    Mod Squad YippeeSkippy's Avatar
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    First checking the water level of your pool- does it only come up to the middle of the skimmer box?
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    Does the door inside the skimmer move freely? It should be floating so that it just lets water spill over it.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    What is the psi on the filter?

    That'll indicate if you have a blockage at the skimmer or in the skimmer line.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    I have no door on my skimmer. I know what you are talking about but this is a different design that does not have one.

    The pressure is normal....but......when I complained about what I thought was a problem with the pump sucking, the contractor placed flow restriction caps on all the pool inlets. The flow from those are very strong, its just that I dont notice things easily flowing to the skimmer. I thought there would be a fairly nice current into the skimmer when it was 100%. Perhaps that is not the case? But there is definitely some blockage from a concrete blob in the intake tube as it turns in the skimmer.

    Filter PSI under normal operation is 12PSI when clean.

    The "current" is important for me because we get a lot of small flies overnight on the surface of the pool and I want to skim it off as soon as possible in the morning. This being our first spring/summer, I dont know if this is going to be the norm, or if its some kind of temporary swarming/mating, as it just started this week when the temps have risen to the 70s overnight.

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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    Please post a picture of the skimmer. If there are restrictors on the outlets, that going to effect the inflow.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    If you have "pinched down" the flow back to the pool, that will naturally reduce the flow into your pump from the skimmer........as pabeader says above.
    Dave S.
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    You should have a weir of some type, the flapper door type is the most common, although there are also round ones that move up and down inside the skimmer. If yours is missing you can buy generic retrofit models, I installed one of these last year and it seems to work well AQUAPower Skimmer Door - OFFICIAL SITE but costs a bit more than some of the traditional generic models (I always had problems with the pump sucking air with traditional weir doors, and have none of that with the aquapower )
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    IMG_5817.jpgThis is what I have. I've inspected it, and I dont see any indication where something else would attach. Also, though there is definitely a blockage in the tube at the bottom of the skimmer, I get a tremendous flow from the jets. A few of them the flow is so strong that you can almost swim in place. Still I dont see a BIG current going into the skimmer though you can see stuff slowly making its way there, but if its a foot or two away, it will pass it.

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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    Here is where hydraulics gets fun! The fact that you have high pressure at the outlets means that you are restricting the flow. Since the flow is being restricted out of the pump, the flow into the pump will also be lessened.

    Think of it this way. Let's say you have 15 gpm of flow and a pressure of 10 psi. If you want to increase the pressure you decrease the flow rate. So at the outlets if you double the pressure you half the flow. Since the skimmer is the source of the water, you will see a decrease in flow rate there too.
    If you were to remove the restrictors your pressure would go down at the outlets but your flow rate would increase.


    That is a simplified example but it's valid. I checked the formulas while I was typing this.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    In plumbing, pressure and head loss are proportional to the square of flow rate. So if flow rate halves, pressure reduces by a factor of 4x.

    However, it is the pump's head curve that determines how the change in head loss changes flow rate but that too is a parabola.

    Also, you really can't go by just the pressure loss at the outlet. The pump will deliver a specific flow rate at a specific total head loss and the outlet pressure is only one part of that. If the filter has higher than normal head loss, the pressure at the outlets will go down but so will the flow rate.

    But I do agree that increasing the size of the return outlet will increase flow rate. How much depends on the pump head curve.
    Mark
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    That's true about head pressure. I was just being simple.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    If the measurements work out you should be able to fit the above mentioned retrofit weir as it is spring loaded with removable tabs / bumpers for universal fit, this is just to address your skimming issue, as to the obstruction that is a somewhat separate issue, but one I think need to be addressed.
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
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    Re: Anyone know recommended GPM flow for skimmer in 100% position?

    I had complained to the builder that there appeared to be a restriction. It seems to me that their answer was to put these restrictors on. The guy they sent to put them on said he didn't know why, just that he was told "to get them on ASAP". Reading some of the posts above I think I understand now.

    - - - Updated - - -

    ohh you have no idea what these people were like to deal with....I would never recommend them. I had to keep an eye on them for everything they did. Not that they were low quality, but rather ATTENTION TO DETAIL was lacking. If I were not at home the day the pump was installed, these dingbats would have installed it across my walkway...that one really alerted me to what I might be in store for. Overall I am pleased, but there were a number of things that I was disappointed with, and they had a terrible attitude of DONT question them!

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