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Thread: How to keep PH from constantly rising....

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    sb127's Avatar
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    How to keep PH from constantly rising....

    Or is that even possible? I've only been BBB for about 2 weeks now, but I'm having to add muratic acid every other day to keep PH in check. It creeps up about 0.2 per day. When it get's up to 7.8, I'll add acid to bring it back down to the 7.3ish range. My TA is 80-90. Of course, I'm having to add baking soda every now and then because the muratic acid is dropping the TA as well. Should I raise my TA to help out with the constant PH increase? If so, to what level? I do have a lot of aeration with the spa spillway running with the filter pump 10 hours a day....plus the kid in the pool a couple of hours a day...plus the waterfall about an hour a day. I don't mind having to add acid to keep the PH in line, but if there is something I can do to cut that down....

    Back when I was using trichlor pucks, that would balance out my PH. The trichlor must have been bringing down the PH pretty close to the rate the aeration was raising it. Of course my CYA was increasing every day, but that's another story.
    20,000G Freeform I.G., Pebble Finish, Rock Waterfall, (2) 2.0HP Jandy Pumps - one filtration & one waterfall, Jandy 60 sq. ft. DE filter, In-floor Cleaning, LXI 4000 Gas Heater, Jandy Aqualink controller, LED lighting

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    Re: How to keep PH from constantly rising....

    You want to let the TA drop a bit lower if your pH is always going up. So quit keeping TA up with baking soda. Try 70. Then try 60.

    I am at 50-something now and pH seems to be very stable at 7.5 - 7.6. I started at 120 I think, and pH was stable at 7.8 - 8.0. Forced it down with MA and aeration to about 90, then let it drop to 70. Then while on vacation and using pucks, it dropped some more. I am keeping an eye on it as normally I'd be adding fill water with high TA but we've had so much rain that has not been necessary. Heck, I may have to get baking soda which just seems weird as my tap water is TA 340 ppm when I last tested. On advice from here I did nudge my CH up to keep the SCI in range, since low TA and low CH is not a good combo for a plaster pool.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Re: How to keep PH from constantly rising....

    Some folks such as those with new plaster or with SWCGs have to chase their pH more than others. Then, even without those things, there are still some of us that for whatever reason just seem to have to add acid frequently. I did that for a while.

    Going to a lower TA as was suggested can help sometimes. For me, I have found that my pool likes the TA to be around 70 or just below. I would suggest that you let your TA fall a little bit, even to 60, and see if that makes a difference. You can also add 50 ppm of borates and see if that helps.

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    Re: How to keep PH from constantly rising....

    Thanks for the advice guys.

    I guess I was backwards in my previous thinking. I assumed TA should be higher (not lower) since alkalinity makes the PH more stable. I wasn't thinking that the PH would just be more stable at a high level and not as easy to move. I'll let my TA fall a little bit and see if that helps. How low is too low? 50? My plaster is also relatively new (~3 months old). At what age does the plaster stop bringing the PH down?

    Ran a few tests this morning, since I hadn't tested TA in a few days. TA was already a little lower than I thought.

    FC = 7
    CC =0
    PH = 7.4
    TA = 70
    CYA = 60
    CH = 320

    I've been reading about borates and may give that a go next pool season. I have a 3 year old that seems to have a hard time keeping his mouth shut in the pool. I doubt he's drinking enough that the borates would be bad for him, but I'd still rather wait until he's a little older. There definitely sounds like no reason NOT to add borates besides the drinking factor. My dog doesn't hardly ever drink pool water, so I'm not worried about her. Borates may be what our pool needs. I'd say our aeration level is on the high side.
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    Re: How to keep PH from constantly rising....

    Somewhat off the subject, but those are very, very nice test results. My guess is your pool water is crystal clear.
    Dave S.
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    Re: How to keep PH from constantly rising....

    Quote Originally Posted by duraleigh
    Somewhat off the subject, but those are very, very nice test results. My guess is your pool water is crystal clear.
    Very much so! Thanks to all of the great advice and knowledge I have learned here at TFP. BBB has made pool chemistry super easy!
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    Re: How to keep PH from constantly rising....

    Plaster takes upwards of a year to cure. So for a full year after having new plaster, you can expect to have to add lots of acid.

    I wouldn't let the TA go below 60.

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    Re: How to keep PH from constantly rising....

    Quote Originally Posted by 257WbyMag
    Plaster takes upwards of a year to cure. So for a full year after having new plaster, you can expect to have to add lots of acid.

    I wouldn't let the TA go below 60.
    So I'm pretty much at the low end of the range for TA if I'm at 70 today. I'll let it fall to 60 and see if that makes any difference. I might should just go stock up on MA and get used to it for a while.

    On a slightly different note, I see you're in Flower Mound not too far from me. Who in the area have you found to have the best prices for MA & bleach? The one time I bought a few bottles of MA was at Lowes it was about $5.50 per gallon. I doubt that's the best price in town. Costco so far has the best price on bleach that I have found. (3) 182oz 6% bottles of bleach for $7.15 so that's not bad. If you know of better prices, I'd love to hear it. I'd love to find a good price on the 12% stuff to cut down on lugging the big jugs. Lowes has 10%, but it's $4.70 per gallon. I'm using about 1 gallon of 6% a day to maintain FC which works out to 3ppm per day FC loss....LOTS of sun on the pool.
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    Re: How to keep PH from constantly rising....

    Quote Originally Posted by sb127
    Quote Originally Posted by 257WbyMag
    Plaster takes upwards of a year to cure. So for a full year after having new plaster, you can expect to have to add lots of acid.

    I wouldn't let the TA go below 60.
    So I'm pretty much at the low end of the range for TA if I'm at 70 today. I'll let it fall to 60 and see if that makes any difference. I might should just go stock up on MA and get used to it for a while.

    On a slightly different note, I see you're in Flower Mound not too far from me. Who in the area have you found to have the best prices for MA & bleach? The one time I bought a few bottles of MA was at Lowes it was about $5.50 per gallon. I doubt that's the best price in town. Costco so far has the best price on bleach that I have found. (3) 182oz 6% bottles of bleach for $7.15 so that's not bad. If you know of better prices, I'd love to hear it. I'd love to find a good price on the 12% stuff to cut down on lugging the big jugs. Lowes has 10%, but it's $4.70 per gallon. I'm using about 1 gallon of 6% a day to maintain FC which works out to 3ppm per day FC loss....LOTS of sun on the pool.
    Usually, I'll go to HD to get the MA. They sell them in the 2 bottle boxes for about $10.20 per box. I also buy my bleach at Costco, although Wal Mart had the Clorox 3-jug cases recently for a little bit less than the Costco price. I'm not sure if that was just a promotion though. I have yet to find a good source for high concentration sodium hypochlorite.

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    Re: How to keep PH from constantly rising....

    If you have borates at 30 to 50 ppm in the water it is fine to lower TA down to 50 (or possibly 40). Without borates I wouldn't go below 60.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: How to keep PH from constantly rising....

    For the MA, not sure if you have warehouse pool supplies in your area, but I get 4 gallons for 19.99. I also get my bleach at sams club for chlorox 6%, it is a 3 pack for around 6.58 or so.
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    Re: How to keep PH from constantly rising....

    I take it you don't have a Menards in TX? I just MA for 3.50 a gal.
    Mona SE MN
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    Re: How to keep PH from constantly rising....

    Quote Originally Posted by sb127
    I guess I was backwards in my previous thinking. I assumed TA should be higher (not lower) since alkalinity makes the PH more stable. I wasn't thinking that the PH would just be more stable at a high level and not as easy to move. I'll let my TA fall a little bit and see if that helps. How low is too low? 50? My plaster is also relatively new (~3 months old). At what age does the plaster stop bringing the PH down?
    Total Alkalinity (TA) has TWO competing effects. It is a pH buffer as you noted so a higher TA will resist changes in pH from additions of acids or bases to the pool. However, TA is also a SOURCE of rising pH itself since it is an indirect measure of the amount of carbon dioxide in the pool. Pools are intentionally over-carbonated in order to protect plaster surfaces and provide some pH buffering, but this over-carbonation results in carbon dioxide outgassing and that raises the pH over time. Also note that this outgassing is faster at lower pH levels so you can not only have your TA be lower but can also target a higher pH in the 7.5 to 7.8 range. Your lowering the pH to 7.3 actually has the pH rise faster early on, but for now that's OK since you are lowering your TA level.

    In your case, you've got additional sources of rising pH including the increased aeration from the waterfalls that leads to faster carbon dioxide outgassing and the fairly new plaster surface which is still curing. The worst of that curing is over since it is greatest in the first weeks to months, but it will still cure for a year or more and technically doesn't stop, but it gets to a low enough rate that you don't notice anymore. If there is a way to turn off your waterfalls, then you can see how much effect they have on the rising pH and get a rough prediction of how much lower the TA might help.

    As noted by others, if you do end up keeping your lower TA level, you will want to compensate by having a higher Calcium Hardness (CH) and/or pH target in order to have the saturation index closer to zero. Note that the curing of plaster will raise your CH levels as well, though by now that rate of rise has slowed down significantly. You can calculate the saturation index using The Pool Calculator.
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    Re: How to keep PH from constantly rising....

    I'm looking into putting together a home made acid injection system, at very low cost. My main issue will be the pumping station is below grade, "flooded", and the filter is sitting, still below grade, but about 3 feet above the pump. I'm going to let the experts guide me on this and start a new thread.

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    Re: How to keep PH from constantly rising....

    Thanks chemgeek! That actually makes a lot of sense. Once I get the TA down to 60, I'll see how difficult it is to hold the PH in the 7.5-7.8 range. I can definitely avoid running the waterfall, but the spa spillway is part of the filtration pump return. If I close the valve to the spa spillway, the water in the spa won't get sanitized.

    I'll keep an eye on my CSI and adjust my CH to keep it close to zero.
    20,000G Freeform I.G., Pebble Finish, Rock Waterfall, (2) 2.0HP Jandy Pumps - one filtration & one waterfall, Jandy 60 sq. ft. DE filter, In-floor Cleaning, LXI 4000 Gas Heater, Jandy Aqualink controller, LED lighting

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