Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 4 of 4

Thread: Trying to Balance my water

  1. Back To Top    #1

    Trying to Balance my water

    My pool is about 4 years old. I have only tested for PH and Chlorine using the OTO type test. I have always had a hard time keeping PH where it should be.

    My pool is about 25k gallons and has a SWCG. I got a better test kit and my current numbers are as follows:

    FC 1
    TC 5
    CC 4
    PH 7.2
    TA 140
    CH 340
    CYA 50

    My PH is low because I am working on bringing the TA down. I have brought it down to 7.0 and am now using aeration to bring the PH back up.

    My biggest concern is the FC. It was at 0 with the TC at .5. I ran my pool over night with the SWG at 95% and the FC came up to .5 with the TC at 1. At noon today I added 2 quarts of Chlorine and then checked my numbers at 5:00pm. As you can see above my FC is still only 1 but the TC came up to 5. That means my CC is around 4.

    So I think this means I need to shock the pool. I read the “how to shock” topic but still have a few questions.

    I think I need to bring the FC up to 24. The pool calculator says to add 5 gallons of Chlorine. Is that all there is to it? My test kit only goes up to 5ppm so I won’t be able to tell if I made it to 24. Also, how long after I shock will it be before the pool is safe to swim in again?

    Any advice on how to proceed would be greatly appreciated.

    Thanks, Scott

  2. Back To Top    #2
    polyvue's Avatar
    Join Date
    Aug 2009
    Sacramento, California USA

    Re: Trying to Balance my water

    Quote Originally Posted by saccrestorations
    I think I need to bring the FC up to 24. The pool calculator says to add 5 gallons of Chlorine. Is that all there is to it? My test kit only goes up to 5ppm so I won’t be able to tell if I made it to 24. Also, how long after I shock will it be before the pool is safe to swim in again?
    According to Chlorine/CYA Chart by Chemgeek the suggested shock level for pool water with a CYA level of 50 is... 19.8 ppm. The Pool Calculator, if I've entered your numbers correctly, suggests a shock level of 16ppm.

    At any rate, be sure about the strength of the bleach. Fresh Chlorox delivers about 6%, if its fresh; you'll need more than 7 gallons to initiate shocking. Most common liquid chlorine, available in pool and discount stores, is Sodium Hypchlorite 10% - about 5 gallons of this product is right to elevate FC to shock level. If you're using stronger pool supply chlorine (12.5%) you'll need less. No-name brand grocery store bleach that has sat on the shelf for months will provide less than 3%, so you'd need 15 gallons of that! Be sure you enter the appropriate bleach percentage in the calculator before deciding what amount to add.

    On the positive side, shocking should be a bit easier with the pH as low as it is. Strongly recommend that you beg, borrow or steal a FAS-DPD chlorine test (from a local pool supply store, perhaps?) so you can measure FC more accurately and prepare diluted sample to ascertain the high amount of chlorine that will result from shocking. I think my kit will test up to 25ppm. Finally, I wouldn't think of letting my guests into the pool until the chlorine is less than 10 ppm and have a personal rule that no one swims until I find that the Combined Chlorine (CC) is unmeasurable -- for me, that means < 0.2 ppm.

    Other more knowledgable folks on this forum will add or subtract from this advice.

    1. Measure the FC level
    2. Add enough chlorine to bring FC up to shock level
    3. Repeat steps 1 and 2 as frequently as practical, as often as once per hour, and not less than twice a day, until:
    a. CC is 0.5 or lower;
    b. An overnight FC loss test shows a loss of 1.0 ppm or less;
    c. And, if you don't have a FAS-DPD test kit, the water is clear.

    Source: Shock Your Pool
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  3. Back To Top    #3

    Join Date
    Mar 2007
    Coastalish 'down easter'

    Re: Trying to Balance my water

    Scott, welcome to TFP!!

    Polyvue has given you VERY good advice

    You really want to invest in a better test kit, either the Taylor 2006 (Leslies sells the same kit, rebranded) or the TF- 100 (linked in my sig). When dealing with a huge cc level, like you have, or an algae issue the FAS/DPD test is the BEST way to go! - You'll save money and be able to be sure that the problem is properly addressed
    Luv& Luk

    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!)

  4. Back To Top    #4

    Join Date
    Jan 2009
    Cupertino, CA

    Re: Trying to Balance my water

    Hear hear to what the others have said.

    I think in general you're best off if you think of the SWG as a way to maintain an FC level, or at best make small adjustments (on the order of 1-2ppm). If you're bringing FC up from zero, or trying to shock, you should use a chemical source, the exact one depending on what else you might try to do simultaneously. (Bleach/liquid CL if your other numbers are okay; dichlor if you want to raise CYA; cal-hypo if you want to raise CH.)
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts