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Thread: Flow Decreases and Pressure raises

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    Flow Decreases and Pressure raises

    36500 gal, DE 48▓ ft. filter.

    Initially, the pump would drop flow and increase pressure from about 18psi to about 25psi.
    Also, there was evidence of air in the pump basket site glass.
    Some small bubbles came out from a jet.

    things done so far:
    1. Replaced ALL pump / motor gaskets, O-rings.
    2. Replaced ALL filter grids and checked for obstructions - no obstructions found.
    3. Replaced Jandy 3 way Valves with independent ball valves at both inlets (1.5" Kreepy Krauley and 2" Skimmer).
    4. Checked capacitor - Good.
    5. Checked and cleaned impeller and diffuser.
    6. Blew out and vacuumed every line and component with shop-vac - No clogs found.
    7. Both baskets are clean.

    I added lots shock and an algaecide to kill it (initially ran it in recirculate to get it all in the water).
    The pool was green but I can see the bottom now.


    After doing all this, the flow is still diminished and the pressure still increases (but now from 12psi to about 22psi).
    There is no longer turbulence or bubbles visible in the pumps basket site glass. Water just moves around.
    No air bubbles from any of the jets.

    Flow will return to normal if:
    1. backwash for a few seconds and start to filter again but will last about 1 hour.
    2. run in recirculate then filter again.
    3. turn the pump off over night.

    The pump runs normal "all day and night" if I run it in recirculate - it does not reduce flow.

    I AM STUMPED......

    ┐┐┐┐┐Any ideas?????
    Last edited by Garrobo; 04-04-2015 at 07:34 AM. Reason: Added / Modify info

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    Mod Squad jblizzle's Avatar
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    Re: Flow Decreases and Pressure raises

    Welcome to TFP!

    What does your water look like?
    Are you adding DE after every backwash? How much?
    Did you ever run it without DE?

    We recommend cleaning the filter when the pressure rises 20-25% over the clean pressure or the flow rate suffers. You might just be waiting too long.

    The lower clean pressure could just be due to the new grids.
    Jason, TFP Moderator
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    JasonLion's Avatar
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    Re: Flow Decreases and Pressure raises

    Welcome to TFP!

    It is very common for the filter to get dirty very quickly, less than an hour, when cleaning up algae. You need to bump, or backwash, the filter. This cycle will often repeat quite a few times before the water is cleaned up.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Flow Decreases and Pressure raises

    Quote Originally Posted by jblizzle View Post
    Welcome to TFP!

    What does your water look like?
    Are you adding DE after every backwash? How much?
    Did you ever run it without DE?

    We recommend cleaning the filter when the pressure rises 20-25% over the clean pressure or the flow rate suffers. You might just be waiting too long.

    The lower clean pressure could just be due to the new grids.



    the water looks much clearer now. still green but I can see the bottom.

    I didn't let it run long with the new grids. I Had DE in the skimmer as soon as it started to suck. I added 9 scoops initially. it ran at about 13psi after the DE.

    I added about 3 scoops of DE after backwash. I didn't fully backwash. I only backwashed for about 5-10 seconds.

    I don't have low pressure......I have high pressure and low flow. if I had low pressure and low flow then the pump would be my suspect.

    I updated the posting with a few things to make it more comprehensible.

    Thank you for your help......

    - - - Updated - - -

    Quote Originally Posted by JasonLion View Post
    Welcome to TFP!

    It is very common for the filter to get dirty very quickly, less than an hour, when cleaning up algae. You need to bump, or backwash, the filter. This cycle will often repeat quite a few times before the water is cleaned up.

    - - - Updated - - -

    The water is a lot clearer now.

    do you think 3 scoops of DE after a normal backwash would suffice on the DE4820 filter? this is what ive seen in several sites.





    PS. Added / modified data to make it more comprehensible.....
    Last edited by Garrobo; 04-04-2015 at 07:51 AM. Reason: make it more comprehensible

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    Richard320's Avatar
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    Re: Flow Decreases and Pressure raises

    You just plain have a clogged filter. A murky green pool can do that to a DE filter in a big hurry.

    A fifteen second backwash wasn't enough to clear off the grids. From my experience, even two full minutes isn't enough to fully clean things -- there's still a lot to clean off when you open the filter and look.

    You do not want this:


    This is what happens when the filter doesn't get fully cleaned before recharging. Click the picture to take you to a tutorial.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Mod Squad jblizzle's Avatar
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    Re: Flow Decreases and Pressure raises

    In you first post you said the pressure used to start at 18 and now it starts at 12 ... That is where my lower pressure comment came from.

    What is a scoop of DE? Ideally, you need to weigh it. Then after a good backwash (which you are not doing) you would add 80% of the full amount.

    So are you following the SLAM process using a FAS-DPD test kit?
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    Re: Flow Decreases and Pressure raises

    Quote Originally Posted by Richard320 View Post
    You just plain have a clogged filter. A murky green pool can do that to a DE filter in a big hurry.

    A fifteen second backwash wasn't enough to clear off the grids. From my experience, even two full minutes isn't enough to fully clean things -- there's still a lot to clean off when you open the filter and look.

    You do not want this:


    This is what happens when the filter doesn't get fully cleaned before recharging. Click the picture to take you to a tutorial.

    I was leaning toward a filter being clogged.
    When I discharged the shop-vac into the inlet, there seemed to be a restriction.

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    Re: Flow Decreases and Pressure raises

    the drop in pressure was after I replaced all the grids.

    and a scoop is one of them blue large cups that sell at leslies.
    http://www.lesliespool.com/leslies-1...coop/14698.htm

    and the short backwash that I performed was just to get it working again. just to see the behavior in other words.

    but most of the comments that ive seen about algae have been similar. algae is my problem!!!!!


    Quote Originally Posted by jblizzle View Post
    In you first post you said the pressure used to start at 18 and now it starts at 12 ... That is where my lower pressure comment came from.

    What is a scoop of DE? Ideally, you need to weigh it. Then after a good backwash (which you are not doing) you would add 80% of the full amount.

    So are you following the SLAM process using a FAS-DPD test kit?

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    Mod Squad jblizzle's Avatar
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    Re: Flow Decreases and Pressure raises

    I recommend you weigh the DE. That scoop is not very helpful ... Depends how packed the DE is in the scoop
    Jason, TFP Moderator
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    Re: Flow Decreases and Pressure raises

    you are not the first to say this.
    is there a scale for this?
    or I suppose I can use my BR scale to weigh the 6lbs it need.

    by the way, after backwash, should I add the entire amount of DE?



    Quote Originally Posted by jblizzle View Post
    I recommend you weigh the DE. That scoop is not very helpful ... Depends how packed the DE is in the scoop

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    JasonLion's Avatar
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    Re: Flow Decreases and Pressure raises

    Scales made for weighing food are better for this situation.

    After a backwash you should add about 80% of the amount recommended in the manual for a full recharge.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Flow Decreases and Pressure raises

    Welcome to the forum Garrobo

    When you get a chance can you also add your pools info to your signature as outlined here - - > http://www.troublefreepool.com/conte...etting-started

    You shouldn't need the algaecide as the chlorine (shock) will kill the algae and if you maintain a proper level of chlorine (FC) it won't have a chance to start again. Most algaecides only prevent, they don't kill so it's just an extra chemical you really don't need.


    Richard, what is it that's in that filter ??
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    Re: Flow Decreases and Pressure raises

    What's in that filter is loads of DE and pool junk from over charge and no backwash.
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    Re: Flow Decreases and Pressure raises

    Quote Originally Posted by jblizzle View Post
    I recommend you weigh the DE. That scoop is not very helpful ... Depends how packed the DE is in the scoop
    I weighed one uncompressed scoop full and it is < 1oz shy of 1 Lb.

    I think that I was using too much DE.

    Much better condition after shocking it and running it since 1300 today.

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    Re: Flow Decreases and Pressure raises

    Quote Originally Posted by Kiss4aFrog View Post
    Richard, what is it that's in that filter ??
    That is DE and algae from insufficient backwashing and cleaning. Packed solid.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Flow Decreases and Pressure raises

    The pool looks much clearer today after the shock and hosing off the grids.

    You guy are much more helpful than the "experts" from Leslie's.

    I did not anticipate that algae would have such deleterious effect on the grids.

    In any case, thank you all for the help and if there are any changes I will sure keep you posted.

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    Re: Flow Decreases and Pressure raises

    Quote Originally Posted by Garrobo View Post
    The pool looks much clearer today after the shock and hosing off the grids.

    You guy are much more helpful than the "experts" from Leslie's.

    I did not anticipate that algae would have such deleterious effect on the grids.

    In any case, thank you all for the help and if there are any changes I will sure keep you posted.
    Thank you for the kind words.

    Do let us know how things are going. Getting people some help and seeing them have success is what keeps us coming back. Glad you found us.
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