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Thread: Supply to Spa - PH drops from 8.0 to 7.0

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    frogabog's Avatar
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    Supply to Spa - PH drops from 8.0 to 7.0

    For reference, I have posted in spas for my dad's octagonal orange hot tub here dad-s-spa-refilled-last-week-and-just-refilled-again-t35175.html

    Dad refilled his 110+ CYA (in two weeks) spa today. The supply line is copper. Same as the whole house.

    Kitchen tap PH is 8.0 which is what the water bureau intends it to be.

    Test in the spa after about an 8-10 minute fill is 7.0 - It might be 6.9. I swear, I tested it within 15 minutes of starting the fill.

    What the heck could cause this? Dad says the ph is always low. He's always raising it.

    Now I figured the rain around here was lowering my ph. He has no rain. The spa is fully sheltered against all weather, although not entirely enclosed.

    Thoughts?
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    Unstable pH? Low TA. Test to find out.
    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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    frogabog's Avatar
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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    Went to check the spa today. I made a huge mistake in calculations likely due to the fact that I was rushing to get out of there yesterday (fail) and put 6oz of dichlor in when I was supposed to put .6 oz.

    OMG CYA was up to 60 today and the chlorine level was through the roof, I stopped when I got to 35ppm on the DPD. MAJOR DOH! I let it circulate and brushed algae off the bubble cover dad uses to keep the heat in, and soaked it in the spa... till dad told me he had more/new that just needed to be trimmed. I figure the major shock was a good thing and and it might have cleared out the system a bit.

    So... we did another drain, this time about 60%. Upon filling I tested the actual fill water before it hit the pool. Right on for city tap water PH at 8.0. So it is NOT in the plumbing.

    That leaves the pool itself, or the filtration system suspect. The green slime (copper obviously) on the filter has been cleaned off. Could that cause it? Would the "scale" on the walls do this? I don't know what kind of scale it is, it's kinda brownish but it's hard to tell because the spa is orangish. The "white" plastic parts such as the skimmer, are creamy with brown stains however.

    TA for fill water was 10. TA in the pool was 40 after filling. I adjusted it to 50ppm w/2tbs plus 1 tsp of baking soda.

    Added calcium to 130ppm. I still have a massive bucket of calcium left.

    Final TC and FC was 7.5ppm. No CC. Much better than 35.

    Adjusted ph to 7.4 from 7.2. Dad has a large bucket of PH Up, so I used that. He had adjusted it last night, but his method is to throw some in, check, and then throw some PH Down in cuz it was too high. I did not do that, pool calculator all the way with particular attention paid to where the decimal point is this time.

    I assume the ph will continue to fall like it always does, but it would be best to find out why. Bear in mind, this is a very old spa. Orange octagonal w/tiles at the water line. I got it from someone about 19 years ago from their house boat dock, it sat upside down in my yard for about 10 years, then I gave it to dad who then spent a fortune and countless hours making it work for him. He added ozone, a monster sta rite cartridge filter, a monster heater, and a monster pump. Monster means HUGE. Overkill, but apparently it works.

    Any ideas are welcome.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Mod Squad Bama Rambler's Avatar
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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    With a TA of 10 it's no wander that the pH stayed low. I'd raise it to about 70 without borates or maybe 60 if you have borates.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    frogabog's Avatar
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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    Duraleigh's post in the other thread told me to do TA at 50.

    PH this am was 7.4. Exactly what I aimed for.

    FC 1.5 this am however. Seems like a large drop to me.

    He is texting me from his spa w/results.

    CYA 30
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Mod Squad Bama Rambler's Avatar
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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    If 50 stabilizes the pH then it's fine, if it doesn't, then raise it some.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    frogabog's Avatar
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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    OK, thank you.

    He says water feels great. shrug...
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    Quote Originally Posted by frogabog
    TA for fill water was 10. TA in the pool was 40 after filling. I adjusted it to 50ppm w/2tbs plus 1 tsp of baking soda.
    Quote Originally Posted by Bama Rambler
    With a TA of 10 it's no wander that the pH stayed low.
    The TA of 10 was for the fill water, not the pool which was initially at 40 ppm but was later raised to 50 ppm. The low TA of the fill water would make it have even less of an influence on the pool's pH. If the spa was made of wood, then tannins could lower the pH.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    Chem geek, if the TA was low and there was any event that would lower pH, like tannins from leaves or wood, wouldn't pH go dramatically low due to low buffering? (chemistry was always a mistry to me, the rules seemed so arbitrary)
    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: Supply to Spa - PH drops from 8.0 to 7.0

    Yes, if the TA of the spa water (not the fill water) was low, then anything that can affect pH such as tannins could change the pH. So for a completely fresh fill using low TA fill water of 10 ppm, then I could see a large pH change, but if adding some 10 ppm TA water to a much larger body of 40 or 50 ppm TA water, the pH should not change very much. Maybe I'm not understanding the original question in this thread -- if it is that the pH drops a lot on a completely fresh fill using fill water with a TA of only 10 ppm (which would be very unusual, by the way), then yes, I can see that the pH could change a lot rather easily.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    frogabog's Avatar
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    Re: Supply to Spa - PH drops from 8.0 to 7.0

    The fresh fill was when ph was so low. The partial fill did not alter the PH at all.

    The original question was regarding how a fresh fill with known PH of 8.0 could become 7.0 in less than 15 minutes.

    When I test TA here at my house at the tap it's 40ppm. Yesterday I tested dad's at 10. Same source, same city. I dunno what happened, but I used R-0007, 8, and 9 for this test and it very clearly turned red with one drop.

    There is a wood deck surrounding the spa, but it does not touch the water. The water filled up quickly, and nothing was put into the water before I tested. It was slightly shocking to say the least to see it fall so much.

    I assume I'll get some spa texts tomorrow morning (dad is a daily spa wake up guy) with report on levels. I also think he ordered a DPD test kit from TFTestkits today because he asked for the link again. Showed him how accurate it is as compared to his K-2005. Now no one will use the 2oz R-0001 and 2 reagents I bought last summer.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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