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Thread: Indoor pool questions

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    Indoor pool questions

    Thanks to all for all the great information provided here!!!

    We are getting closer to completing our indoor pool. Here are a few of the details...

    Indoor pool
    20,000 gal pebble finish
    In-Pool spa
    4x160 Pentair pump
    2hp Pentair pump
    Pentair 320 cartridge filter
    400k Pentair gas heater

    I would like to go with the BBB method using a very low CYA/ FC level. My preliminary plan for pool chemicals would be to have no CYA and a .2ppm FC. I've read this is very difficult to attain, so I am open to a 5-10ppm CYA and .5-1ppm FC.
    Would there be any issue with adding chlorine just before closing the autocover or should autocover be left open for awhile?
    How much MPS should be added to a 20k pool for shocking?
    How often should I shock(2-3 persons using on a daily basis)
    Can a stenner pump system maintain a .2ppm FC level for my pool?


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    In the Industry

    frustratedpoolmom's Avatar
    Join Date
    May 2007
    SWSuburban Chicago, IL

    Re: Indoor pool questions

    I think the MPS is 1 lb bags for 10,000 gallons so 2 bags? Not super sure but thought I would give this thread a bump.

    I know zip about indoor pools. Hopefully someone who does will be along to advise.

    Good luck!
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    Perfectly Clear Pool Service, Find me on Facebook!

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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Indoor pool questions

    Even if you could have 0.2 ppm FC with no CYA in your pool, it wouldn't be enough reserve to not get used up completely locally with sweat/urine and other contaminants. It's not just impractical to maintain the low level, but it just doesn't work. You need sufficient FC in reserve to prevent it from going to zero locally. The easiest way to do that while having the effective "active" chlorine concentration be low is through the use of CYA.

    So I would recommend going with 20 ppm CYA and 2 ppm FC since 2 ppm FC will be plenty of reserve even for somewhat higher bather loads. Also, 20 ppm CYA can be measured in the CYA test in the TF100 test kit from This 2 ppm FC with 20 ppm CYA is technically equivalent to 0.2 ppm FC with no CYA, but will be easier to control and manage. You can, of course, try 1 ppm FC with 10 ppm CYA where you are estimating the latter and see how that goes -- I just think it's going to be hard to know that CYA level.

    As for non-chlorine shock, you might not need it. If the chlorine level is well maintained, you might avoid getting CC's. Measure for CC's in the morning since that gives overnight for them to be removed by the chlorine. If you do measure some and you want to use non-chlorine shock, then you can just use the recommended amount -- but realize that excess, especially for the first day, will measure as CC on tests unless you get the MPS interference remover (and there have been mixed results with that). I would try and avoid using MPS if you can and see if you can't manage the pool with chlorine alone -- at least give it a try.

    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Indoor pool questions

    Thanks for the replies.

    Being an indoor pool, we are attempting as low chlorine level as possible. I know if we keep a well balanced system we shouldn't have any chloramine problems and the smell that comes with it. I have ordered the TF100 test kit and wasn't sure how to measure a lower CYA level. I think I will go for the 10ppm CYA and 1ppm chlorine and calculate a 10ppm CYA for a 20k pool. I'll keep a close eye(not closed) on CC as far as shocking the pool with MPS.


  5. Back To Top    #5

    Re: Indoor pool questions

    there is some indication that UV might be useful in indoor pools to help combat CC. A peristaltic pump can supply your chlorine but to accurately control the amount according to demand you will need an ORP controller which will measure ORP and not FC levels.

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    Re: Indoor pool questions

    From what I've read about the negatives of UV is that 1) upfront cost 2) it will break down chlorine and
    3) have to run longer water turnovers to break down CC.

    What are the negative impacts of using BBB and shocking with MPS?


  7. Back To Top    #7

    Re: Indoor pool questions

    Quote Originally Posted by swimmingsoon
    From what I've read about the negatives of UV is that 1) upfront cost 2) it will break down chlorine and
    3) have to run longer water turnovers to break down CC.

    What are the negative impacts of using BBB and shocking with MPS?

    Poor indoor air quality and often persistent CC.

  8. Back To Top    #8

    Re: Indoor pool questions

    Thanks Waterbear.

    HVAC/ Dehumdification system will hopefully keep humidity in check and circulate fresh air into the room.
    It doesn't sound like you are a big fan of MPS as an oxidizer or am I reading between the lines?


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