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Thread: Should I lower pH while draining/refilling to lower CYA?

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    Should I lower pH while draining/refilling to lower CYA?

    Hey everyone, long time lurker, first question that I couldn't find on the site.

    I'm a new owner of an old pool. I googled how to take care of a pool prior to closing and stumbled on this site. Its great!

    When we got the keys the pool was clear, but there were what was left of approximately 10 small chem discs in the skimmer basket. (I assume dichlor or trichlor)

    I fired the pool guy when he showed up one day, the old owner didn't even tell him the house sold. So I guess he was a once in 3 weeks guy.

    Pool size: 28000 gal
    Initial readings:
    FC: 9.0
    CC: < 0.5
    pH: > 8.0
    ALK: 220
    CH: 800
    CYA: >100

    We have had rain off and on for the past week or so. I have been draining/diluting for the past 3 days. I am slightly concerned with floating the pool so I have been draining the first foot or so from the shallow end. When it gets down a foot I have been filling while continuing to drain. I fill with the hose at the bottom of the deep end. I do this until morning.

    Current readings:
    FC 10.0
    CC: 0
    pH: >8.0
    ALK: 150
    CYA: approx 150 (Diluted 1 part pool water with 2 parts distilled)


    Fill Water:
    pH: >8.0
    ALK: 110
    CH: 150


    So the question is: Should I bother to try and lower pH while doing the drain/fill for the next week or so?

    Also we are on a slight hill, what is the most water that would be considered safe to remove prior to filling? As in how many feet?

    Shallow end 3 ft, deep end 8.5 ft, rectangle.

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    JasonLion's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Welcome to TFP!

    Normally I would say no, but you have high PH, high TA, and high CH, which is a recipe for calcium scaling. You will likely save yourself a great deal of trouble if you take care of that right away, meaning next day or two, as opposed to next week or two. I would lower the PH to 7.2 right away, and after each cycle of water replacement (there might only be one such "cycle" but it could easily take a couple of rounds). That will lower PH right now, and start working on lowering TA. The water replacement will then help with lowering CH, all of which will help prevent calcium scaling.
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    Richard320's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Welcome!

    The odds of floating your pool in SoCal are pretty slim unless you're right near the ocean or a creek or lake or something that's full of water. Take a look at the nearby creeks or percolation basins. Odds are they're dry, despite the meager rainfall we've had recently.

    Where exactly are you? There's a huge difference between, say, Palm Springs and Newport Beach.
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Quote Originally Posted by Richard320 View Post
    Welcome!

    The odds of floating your pool in SoCal are pretty slim unless you're right near the ocean or a creek or lake or something that's full of water. Take a look at the nearby creeks or percolation basins. Odds are they're dry, despite the meager rainfall we've had recently.

    Where exactly are you? There's a huge difference between, say, Palm Springs and Newport Beach.
    Simi Valley.

    - - - Updated - - -

    Quote Originally Posted by JasonLion View Post
    Welcome to TFP!

    Normally I would say no, but you have high PH, high TA, and high CH, which is a recipe for calcium scaling. You will likely save yourself a great deal of trouble if you take care of that right away, meaning next day or two, as opposed to next week or two. I would lower the PH to 7.2 right away, and after each cycle of water replacement (there might only be one such "cycle" but it could easily take a couple of rounds). That will lower PH right now, and start working on lowering TA. The water replacement will then help with lowering CH, all of which will help prevent calcium scaling.
    So with fill water pH > 8.0 , and my pool >8.0, should I add acid based on 8.0 or more than 8.0. I'm asking what to put in the pool calculator?

    I did use the pool calculator prior to the draining to try and lower pH, but even with all the acid I added I still didn't get below 8.0. I'm using Taylor K-2006

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    Richard320's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    First, about ground water: Select groundwater depth and zoom in. The measuring wells will show up if you zoom in far enough and tell you how far down you need to dig to strike water. http://gis.water.ca.gov/app/groundwater/ If it's well below your pool depth, no worries.

    If you are off the tester above 8.0, use 8.0 in poolmath, add acid, give it half an hour to mix - maybe brush some to help speed it up-- and retest. Repeat until the pH comes down into range. Or, if you have the acid demand test in the K2006, that will tell you.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Is it not true that ANY pool can be partially drained down to winter levels without floating? (just a few inches below returns)
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    JasonLion's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    borjis, that is almost always true. In extremely swampy soil it is possible for ground water to be nearly at the surface, which would pose a problem for even a small partial drain. This is both very rare, and fairly obvious. If your area is like that you will know about it.
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    Re: Should I lower pH while draining/refilling to lower CYA?

    An update after 4th day of draining...

    Taylor K-2006
    FC: 8.0
    PH: >8.0
    CYA: >100 (Strip test) * Only have 1 test left of CYA reagent. More on order.

    Draining again..

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    Re: Should I lower pH while draining/refilling to lower CYA?

    An update.

    Taylor K-2006:
    FC: 8.0
    CC: < 0.5
    PH: 7.4
    TA: 120
    CYA: 70 ish ( I find this hard to read)
    CH: 400

    I took a sample to Leslies to compare the results...
    Leslies:
    FC: 10.0
    PH: 7.5
    TA: 100
    CYA: 40 !!!


    So I re-ran my test and got approx 70 again for CYA, I had my wife try the test without telling her my result and she got around 70 as well.

    I tested my TA again and got the same result 120.


    1. Would you advise trying to lower the TA to the recommended 70-90 range (by adding acid), while still trying to drain/refill to lower CYA?

    2. Is there a more accurate kit/test for CYA? At Leslies he fills a skinny tube completely and then uses a sliding dot to read the result. Is this any better than whats in the K-2006? I have been pouring my solution back into the dropper bottle to read it again to verify my results.

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    Mod Squad jblizzle's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    1. TA is nearly the last thing you should worry about ... after you are bored with everything else.

    2. Nope. The Taylor CYA test is the best there is. The sliding tube is basically the same test ... and you already see why we do not trust pool store testing ... especially for CYA. No problem pouring the solution back and forth a few times to see if you are consistent. Make sure you are doing the test outside in bright indirect light (sun behind you) with the tube at your waist.
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Todays Test:

    FC: 9.0
    CC: <0.5
    pH: 7.6
    TA: 120
    CH: 350
    CYA: 40-50 <- It is overcast and drizzling here so I can't really tell. I got around 50 outside under patio cover, and around 40 in well lit bathroom. I will test again when the sun is out.

    Should I start working on getting the TA lowered now?

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    Mod Squad jblizzle's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Quote Originally Posted by TK-421 View Post
    Should I start working on getting the TA lowered now?
    Why? There is no reason to worry about it. Just keep the pH in the 7s.
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Quote Originally Posted by jblizzle View Post
    Why? There is no reason to worry about it. Just keep the pH in the 7s.
    I thought the recommended level for TA in a plaster pool was 70-90 ?

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    Mod Squad jblizzle's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Look again ... 70-90+

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    They are just guidelines not absolutes.
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    Richard320's Avatar
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    Re: Should I lower pH while draining/refilling to lower CYA?

    Quote Originally Posted by TK-421 View Post
    I thought the recommended level for TA in a plaster pool was 70-90 ?
    It says 70-90+. If you need to raise TA, you need a target to plug in to get the baking soda dosage. If by some weird coincidence, 90 requires 3.5 lbs, and you have a four pound container, it means just dump it all in. It's not that critical. But it also means that if your TA is well above 90 - which could easily happen in California - don't worry about it. If your TA is 100 now, it's in range. It's 90+. Just plug your current value into the target and go on. The exception is if the CSI is really high, which can happen when CH gets really high. But that's an advanced topic we don't need to worry about until you get the basics mastered.

    TA is the least important parameter you test. If you maintain the pH, each time you add acid, the TA will go down a little bit. Eventually, you should hit a sweet spot where the pH holds steady for a week or more. When that happens, that's where you want to keep your TA. You'll only learn that after a few months of careful testing, though.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Should I lower pH while draining/refilling to lower CYA?

    Quote Originally Posted by Richard320 View Post
    It says 70-90+. If you need to raise TA, you need a target to plug in to get the baking soda dosage. If by some weird coincidence, 90 requires 3.5 lbs, and you have a four pound container, it means just dump it all in. It's not that critical. But it also means that if your TA is well above 90 - which could easily happen in California - don't worry about it. If your TA is 100 now, it's in range. It's 90+. Just plug your current value into the target and go on. The exception is if the CSI is really high, which can happen when CH gets really high. But that's an advanced topic we don't need to worry about until you get the basics mastered.

    TA is the least important parameter you test. If you maintain the pH, each time you add acid, the TA will go down a little bit. Eventually, you should hit a sweet spot where the pH holds steady for a week or more. When that happens, that's where you want to keep your TA. You'll only learn that after a few months of careful testing, though.
    Thank you for your thorough reply. I have already created my daily log sheet to keep track of everything. I will see how my pool responds over the next few months.

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