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Thread: Question about PSI

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    Robbie Weise's Avatar
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    Mar 2013
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    Question about PSI

    This is my first post, I've done a lot of searching here but can't quite find an answer to my exact question.

    A little about me first:
    I have a 13,700 gallon gunite pool that was finished March of 2012. The company that built the pool provided us with six months of service but since then I've taken it on myself. I've found it to be a very rewarding experience and I've learned a lot in the last year or so.

    I'm in South Carolina and we should start getting warm weather very soon so this weekend I decided to get a jump on getting the pool ready. I really didn't do much all winter but the water has stayed nice and clear the entire season. I decided that I wanted to break down my filter and clean everything real good since it hasn't been done yet up to now. I have a Pentair Quad De 80. Over the summer I probably backwashed about 4 times or so and refilled with 8lbs of DE. The filter runs at 10 psi when clean and I would backwash at 15.

    The guy at the pool store yesterday talked me into getting Zeofiber. I like that I could use so much less so I was pretty easily sold. After tearing everything down and putting it back together and putting about 20 cups (regular cup, not a DE cup) of the fiber in I'm running at 6 psi. The pool almost looks like a spa with how hard the jets are pushing water back in the pool.

    Herein lies my question, is the lower psi ok? Is it normal because of how much cleaner my cartridges are now? I should say that the filter had a substantial amount of DE inside of it. Not just on the cartridges but all inside the filter. I took some pictures, I'll post them up. I'm also curious if the Zeofiber would cause the drop in psi. I plan on cleaning the pool again today real good and then keeping an eye on it, if everything stays clean I guess I'm good. Just like with the DE, I always feel like I'm not putting in the right amount.

    Thanks for the help, sorry if this is in the wrong place or if I rambled on too much.

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    Re: Question about PSI

    Welcome to TFP!

    Clean filters can cause the conditions you describe. Because the flow is so much better without all of the resistance that it had previously with the old DE, things are moving through better.

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    Robbie Weise's Avatar
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    Re: Question about PSI

    Hey, thanks for the fast reply! Makes perfect sense, I guess I was just a little surprised for some reason. Here's another question for ya, is this amount of DE in the filter normal? It's been since last summer since I've backwashed. I was kind of shocked to see how nasty it looked.




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    JasonLion's Avatar
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    Re: Question about PSI

    Seeing that much DE in a filter is unfortunately common enough, however it is not a good thing. You should be backwashing much more frequently, any time the filter pressure goes up by 25% from the clean filter pressure.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Robbie Weise's Avatar
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    Re: Question about PSI

    I'm hoping to get a better handle on everything this year. It's slowly all starting to come together and make sense to me.

    This site is a great tool, I'll be hanging out here a lot I'm sure.

    A side conversation on minimum flow rate for backwashing has been moved here.

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