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Thread: Difficulty keeping chemistry right

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    Difficulty keeping chemistry right

    I've had my pool for 8 years and it seems like every summer I have a hard time keeping the chemistry correct. Along with the solar heater and our location; Tampa, and with the pool water nearing 90 deg it seems almost impossible to keep the chemistry correct. This last week we were out of town for 5 days and came back to a green pool. I know how to fix it but I'm thinking of getting a chlorine tablet dispenser to replace the SWG during the hottest part of the summer.
    The SWG seems to require the pool chemistry to be almost exact for it to work properly and that becomes impossible when on vacation. A SWG and the high rain and temps we get in Tampa require adding acid daily. I could get an acid dispenser but I think using chlorine tablets which seem to keep chlorine in the pool even if the PH varies a little, during the warmest months would solve this problem.
    Suggestion and Comments.
    Thanks
    Tim
    Tim
    10,000 gal concrete pebble tech
    SWG. 8 yo, Cartridge filter
    Pentair single speed pump, Solar Heat
    Tampa, FL

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    DaninFLA's Avatar
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    Re: Difficulty keeping chemistry right

    I am in Florida, just an hour south of you and have a SWCG as well. what size cell do you have?

    What kind of test kit do you have? do you have one of the recommended test kits (see the link in my signature). you don't want to use chlorine tablets as they increase your CYA amounts and that increases the amount of chlorine you need in your pool. your problem is most likely that you are keeping your chlorine levels too low and you have algae present. you can have algae present even when the water looks clear. once it starts, the SWG cannot create enough chlorine in the water to overcome the algae. the SWG is great at maintaining your chlorine levels in a pool with no algae. you need one of the test kits and to go thru the SLAM process (see pool school). its going to take a few days. stock up on liquid chlorine from the pool store (I get mine at leslies) and order a test kit.

    the key in a SWG (and all pools for that matter) is to start with a pool with zero algae. you do that via the SLAM process. once you are done, the SWG will be all you need to maintain your pool. As long as you keep your chlorine levels above the minimum for you CYA level, algae will never start to grow and you will have a sparkling pool

    as far as your pH issue, once again, need one of the recommended tests so you can determine your TA (total alkalinity). when this is high, you will get very quick pH rises. the solution is to keep adding muriatic acid to lower your pH to around 7.2, then let it rise, repeat, etc. this eventually will lower your TA to a point where you pH rise slows down quite a bit. I am down to adding a little muriatic acid once a week now that my TA is down to about 60ppm

    Also, when you said "I know how to fix it"...how is that? if you are referring to a one time shock, that will not fix it. the solution is a SLAM, which you basically keep your pool at shock level for several days until 100% of the algae is killed and removed. only way to do a SLAM is with the proper test kit...pool store testing is NOT reliable and will not work.
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    Mod Squad JVTrain's Avatar
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    Re: Difficulty keeping chemistry right

    And your pH rise issues are likely an issue with your TA level. What is your TA at right now? Are you adding baking soda to bring the TA up to a specified range? Recommended TA for SWG pools is lower than manually chlorinated pools because the SWG creates a good amount of aeration inside the cell. If you have a lower TA value (as low as 60) your pH rise will be slower.

    Welcome to TFP!
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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    Re: Difficulty keeping chemistry right

    Thanks for the quick response. TA now is 80. Perhaps that is too high and why the PH is so high. I've had to add alkalinity up due to all the rain we've had.
    I have the strip test kit that tests PH, TA, FC, and CA. I also use the vials that test PH and chlorine.
    Pentair 20,000 gallon SWG.
    Will study the SLAM procedure.
    Tim
    10,000 gal concrete pebble tech
    SWG. 8 yo, Cartridge filter
    Pentair single speed pump, Solar Heat
    Tampa, FL

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    Mod Squad JVTrain's Avatar
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    Re: Difficulty keeping chemistry right

    Go ahead and let the TA drift down toward 60. TA will decrease any time you add acid to the pool. No need to keep the TA higher than 60. I think you'll find that your pH rise will be slower. If it does drop below 60, only bring it up to 70 or so again.

    Test strips are fairly worthless. They're inaccurate and the ranges provided for the color match is not meaningful or accurate enough for proper pool maintenance. I would highly recommend getting a test kit that can properly test for FC, CC up to 50 ppm and for sure a CYA test. The TF-100 from tftestkits.net is the best value for residential pool test kits. It has all the tests you need and enough reagents to get you through an entire season (or more) for regular maintenance.

    It's important to know the basics about the methods we teach here. Start with ABCs of Pool Water Chemistry and explore some of the other articles in Pool School as you can.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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    DaninFLA's Avatar
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    Re: Difficulty keeping chemistry right

    Tim, its hard to give advice based on numbers that are not reliable. the test strips and pool store results are not accurate, so we cant make recommendations with bad information. if you are serious about taking over your pool and understanding it, you gotta invest in a real test kit. It will be the best $70 you ever spend and if you are committed to the TFP way of doing things, you will have a sparkling clear pool with no algae outbreaks.

    there was no reason to add alkalinity up due to the rain, not sure where that's coming from?

    unlike a pool store, we don't have anything to gain from recommending products here....but we do recommend the test kits so you know precisely your levels. the basics of TFP is to know precise levels in your pool and only making modifications/additions that are needed based on those results. I promise you, it will be the best decision you ever make.

    in three weeks, you will be answering people's questions and know how your pool operates.
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    Re: Difficulty keeping chemistry right

    Thanks Dan, I took a sample of water in to the pool company and found the TA higher than I thought - 95. I added 4.2 gallons of chlorine as recommended by the pool Math calculator.
    Since you have a salt water pool I'm guessing you also have a SWG. If so how long do you run your pump during the hottest part of the summer and what percentage is your SWG set at.
    Tim
    10,000 gal concrete pebble tech
    SWG. 8 yo, Cartridge filter
    Pentair single speed pump, Solar Heat
    Tampa, FL

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    DaninFLA's Avatar
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    Re: Difficulty keeping chemistry right

    I run my pump for 5-6 hours and my cell is around 40% output, and I have a 40k cell for a 10,000 gallon pool. however, if I had algae in my pool, I could run my pump 24/7 and SWCG at 100% and it wouldn't matter, and my chlorine levels would be too low and wouldn't stop the algae....I wouldn't be able to keep up. You gotta get rid of the algae first. you cant figure out your required chlorine until you know your CYA amount. you are just guessing at this point, and its going to be hard (impossible) to complete a SLAM without the proper test kit.

    Have you looked into the test kits yet? your test strips and/or pool store tests are not accurate. especially for CYA which is the most critical piece of info we need to help

    BTW, you said you added 4.2 gallons of chlorine??? that's over 40ppm of chlorine, way too high. where did you get that from??
    hopefully that was a typo
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    Re: Difficulty keeping chemistry right

    I ordered the TF-100 test kit. In the meantime I took a sample to the pool store: FC: .76 PH: 7.4 TA: 95 CYA: 67.
    Based on the CYA of 67 and using the CYA chart to determine Shock FC, I arrived at a Shock FC of 27. Using the pool math calculator it arrived at a figure of 4 gallons and 1 qt of chlorine to get the FC to 27 based on a starting FC of .76 and a CYA of 67.
    Tim
    10,000 gal concrete pebble tech
    SWG. 8 yo, Cartridge filter
    Pentair single speed pump, Solar Heat
    Tampa, FL

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    Re: Difficulty keeping chemistry right

    I super-chlorinated as mentioned above and went back to the pool store with a water sample. The results 17 hours after I added the 4.3 gal of chlorine:
    FC: 14.75
    PH: 7.9
    CYA: 62
    TA: 90
    Tim
    10,000 gal concrete pebble tech
    SWG. 8 yo, Cartridge filter
    Pentair single speed pump, Solar Heat
    Tampa, FL

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    DaninFLA's Avatar
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    Re: Difficulty keeping chemistry right

    any update? hard to make any adjustments based on CYA results from a pool store. maybe you got lucky, no way to know until the test kit comes in
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    Re: Difficulty keeping chemistry right

    Got the test kit. I haven't done anything to the pool for several days. Checked chemistry this morning with the new test kit. Chlorine is still high. PH is good, TA - 90, and CYA is 90. TA is a little high and will let it decrease naturally. CYA a little low and will add stabilizer in a couple of days. Water right now is crystal clear. Left this AM on a trip will return Saturday and check again. Test kit is good, I need to find an eye dropper for precise measurements. I did add acid as I'm gone till Saturday and don't expect grown son or wife to add any.

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    Re: Difficulty keeping chemistry right

    Whoa....don't add any stabilizer. Your CYA level is already a little high, even for a SWCG. See chart here...Pool School - Chlorine / CYA Chart

    The 70-80 range is what is recommended for a SWCG.
    17K gal, AG, 1.0HP pump, 300lb, 3.14 sqft, 62GPM sand filter, Pool Pilot Nano SWG, TF-100 Test Kit

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    Re: Difficulty keeping chemistry right

    Oops, just checked my notes, you're right. Will leave it alone.

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