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Thread: Green water, pool water test confusing

  1. Back To Top    #1

    Join Date
    Jun 2015
    Montreal, Canada

    Green water, pool water test confusing

    Let's give this a try, it's a first for me. I have an inground vinyl pool 16 x 32 (roughly 80,000L). We opened it the first weekend in June, I live in Montreal Canada.
    We did all are usual steps and all was good within a few days. I test the water on a regular basis but I must add, I do not have one of those super fancy testing kit although it does test the chlorine, ph, acid demand and alkalinity. I also have the strips. Last week when I tested, my chlorine was high (FC) 5 but it was saying my PH was 6.5 and TA 0. I proceeded to test with the other kit and it showed the same results for the PH, so I did the TA test and it said to add 2.79 kg of soda ash (sodium bicarbonate). During all this time, algae is forming, so we added algaecide. I did add the soda ash and not much has changed. So I bought another kit figuring mine was old and the products were no longer effective.

    The new kit showed the FC between 1 & 3, PH was 6.5 so I proceeded to the TA test. It requires 2 drops of ALK-10, then 5 drops of ALK-20, which is green and the instructions does say the sample will be green. This is followed by adding a drop at a time of ALK-30 until the sample turns red. Well when I put the 5 drops of ALK-20, my sample goes red right away which leads me to believe the alkalinity is too high! Am I correct to assume this? By what I've been reading, if this is the case, my PH should be up as well and it's not. We are not quite sure what to do next and I totally agree, pool store do a fine job of selling us all sorts of chemicals/products. Tonight, we superchlorinated. Certainly hope to see an improvement in the morning.

    Can I add PH+ to up my PH without it affecting the TA? I know they are related somehow but not sure how to go about it. We did not have this issue last summer. We have add a lot of rain lately and gorgeous weather is forecasted and I want to be able to swim in my pool.

    Extra info - I have a sand filter - Hayward Pro Series High Rate Sand Filter.
    Any help you can provide would be greatly appreciated.


  2. Back To Top    #2
    aussieta's Avatar
    Join Date
    Jan 2014
    Langwarrin, Victoria, Australia

    Re: Green water, pool water test confusing

    welcome to tfp
    it is difficult to help people with unreliable test kits
    so we encourage people to buy a taylor based kit
    in canada the taylor k-2006 is the best bet i use the k-2006c as it has more reagents
    not sure which test kit you are using
    but to increase ph with high ta
    best approach is aeration
    pointing returns up to break surface
    you can add washing soda or soda ash or borax
    i would suspect your ta is actually very low
    in which case you need sodium bicarbonate
    SWG inground peanut shaped painted concrete pool
    50,000 litres 13,000 gallons
    Lincoln Salt Chlorinator, 25 gram cell Sand Filter
    Taylor K2006-C test kit, Taylor K-1766 salt test
    are you taking care of your pool or is the poolshop taking care of you

  3. Back To Top    #3
    Mod Squad
    Join Date
    Aug 2012
    DFW, TX

    Re: Green water, pool water test confusing

    Welcome to TFP!

    +1 on getting a K2006 test kit.

    Use Borax to raise PH with little effect on TA. More about Pool School - Recommended Pool Chemicals

    Algae grows because there is not enough chlorine in the pool for the CYA level. It is important to keep chlorine above the minimum level at all times to sanitize the pool and keep it algae free. Chlorine CYA Chart

    Please add your pool info in your sig as shown here, Pool School - Getting Started
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