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Thread: Rising pH and SWG

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    Join Date
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    Rising pH and SWG

    My plaster pool with a SWG was always running up the pH. If I balanced it down to 7.5, it would raise to 8.0 in 2-3 days. I could add a cup or two of acid daily.

    I recently did a drain and refill for maintenance, and this time, I switched to a full BBB using bleach versus SWG to see if there was a difference. Of course, I need to add bleach every day, but my thinking was that I could run it without salt for a month or two and have some comparison. Net, I can always add salt - it's tough to take it out. I have noticed the pH rise going up more slowly, so that's a good outcome. Now, I am adding about 2 cups every 4-6 days.

    I have a hypothesis that I wanted to run by the forum. My pool has an attached spa with a overflow from the spa to the pool. Since the controls are manual, the pool was set to feed both the spa and pool the entire time the pump was running; therefore, the spa overflow is always running. Now that the pool uses bleach, I am not running the pump as long (6-7 hours versus 12 hours). Here's my question: can the quick pH rise be attributed to the aeration of the water versus the use of SWG?

    These past few days I have turned the spa return off and noticed very little change in the pH. But it will take a much longer test to tell for certain, as rain and sun will create variables that can affect the balance.

    I do travel for a living so it's not practical for me to do daily monitoring, which is why I opted for the SWG. I don't want to use tablets, and we are heading into the 80's-90's here in central Texas now so the balance demand is only going to go up. I'm looking for the best set up that will work for my lifestyle.
    16,000g in-ground plaster pool, attached spa, BBB, DE Filter, SWG

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    Re: Rising pH and SWG

    This is normal. Aeration of any kind, whether it be SWG or other methods, will raise pH. Can you please post your TA level? TA should be in the 70 range to help with pH drift. Also, adding borates to 50 ppm can help with this too.

    I only check my pH a couple times a week currently, mainly because I've recently replastered. Before the replaster, I only checked once per week. I would get up into the 7.8 to 8.0 range after a week, so I'm not afraid it was drifting too high between checks.

    I also travel for a living. I'd be toast without my SWG.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Re: Rising pH and SWG

    Thanks.

    I forgot to add the readings:

    TC/FC=4.0
    pH=7.5
    CYA=40
    TA=120
    CA=300

    I am considering using borates, but I wanted to address one thing at a time. Once I have isolated the swift pH drift, I may end up back to SWG (assuming it's aeration).

    I also noticed that my spa plaster was taking a bit of a beating - it's very corse/rough in patches. The pool contractor that did my maintenance suggested that this is very common when a significant amount of the return flow is directed towards the spa to run the overflow. He suggested that the fast moving water and higher concentration of chlorine from the SWG may be the culprit. He recommended that I give the spa a break.

    Does that make sense?
    16,000g in-ground plaster pool, attached spa, BBB, DE Filter, SWG

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    JasonLion's Avatar
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    Re: Rising pH and SWG

    Lowering TA to around 70 will help a great deal with the PH increases.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Mod Squad jblizzle's Avatar
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    Re: Rising pH and SWG

    I think their explanation of the spa surface is bogus. The FC level out of the SWG is only slightly higher than the bulk of the pool and for a little spillover I would not think the water velocity is very high.
    Jason, TFP Moderator
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    UN1017's Avatar
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    Re: Rising pH and SWG

    As Jason stated, lowering that TA will make a big difference. Fortunately, it will be pretty easy for your setup. Once I got my TA down, my pH settled quite a bit. Just make sure you get your TA down before if you decide to borate.
    15'x30' IG - Roman-style - 14K - Pebble Fina Classico
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    Re: Rising pH and SWG

    When you were using the SWG, was the CYA level at the same 40 that it is now? The forum suggests (and your SWG manual probably says) to run at CYA of 75-85 in the Deep South. This allows the SWG to run less to keep up with losses due to sunlight. It may be that adjusting the CYA would allow you to go back to the SWG. (Wish I had a SWG but can't due to soft rock everywhere)
    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: Rising pH and SWG

    Sorry for the delay - out of town.

    I did have my CYA up more towards the 70-80 mark for that reason.

    I will work on adjusting my TA down. Unfortunately, that was the TA of the fill water - but I was thought the higher TA would help with pH bounce so I kept it there. I have run my pool only for a few days, testing each day. Then ran the spillover for a half day and sure enough, the pH goes up much more quickly.

    My strategy is this:
    1. Bring the TA levels down and stabilize
    2. Up my CYA
    3. Begin adding salt and start up the SWG

    I'd much rather not use the SWG, but it's the only means to keeping the levels sane while I'm away. I'll toggle the spa spillover on/off. Once we hit Texas summer, the room for error goes down dramatically.

    I'm still deciding about borates... but that's another thread
    16,000g in-ground plaster pool, attached spa, BBB, DE Filter, SWG

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    JasonLion's Avatar
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    Re: Rising pH and SWG

    TA has two effects on PH. First it helps buffer PH, slowing down any changes, but second it tends to drive the PH up (especially if there is any aeration, which the SWG provides).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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