Keeping TA up in small tub

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
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iamcanadian

Keeping TA up in small tub

Postby iamcanadian » Fri 13 Oct, 2017 00:00

Hello Pool People, My issue really isn't an issue other than down time. In my public aquatic center we have 2 small hot tubs ( one at 500 Gallons other 750 Gallons) We use liquid CL2 at about 3% after mixed. Our target is between 3-4 ppm and of course a 7.5 ph. Muriatic acid to bring ph down and Sodium Bicarbonate to boost TA. Now with the size of these Tubs and the usage from customers the TA needs to be boosted at some point in the afternoon as ph starts to drop when TA drops below 40-50 ppm. Because out fill water is almost perfect at ph around 6.9 and TA over 100 ppm (105-110 ppm) In order to get longer life in these tubs we try to dump almost half the water out and add half lb of sodium Bicarbonate to get TA around 120-130 ppm with ph closer to 7.5. My question is..... Is there a product out there that would bring my ph down still but doesn't kill my TA. Would dry acid be better? What is this ph down ? would it be a better answer. We have tried to delute the acid as much as possible but TA always dies quickly...

Cheers
Shawn


Denniswiseman
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Re: Keeping TA up in small tub

Postby Denniswiseman » Fri 13 Oct, 2017 03:10

Why do you need to raise your TA
TA and pH are basicly reliant on each other. A high TA will raise your pH, a lower TA will stabilise your pH. You are Yo-Yoing with your water treatment
Dry acid add sulphates to your water
Liquid chlorine (sodium hypochlorite or plain bleach)
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA
CanadianPoolGuy
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My Pool: Hello all, I work at a public aquatic center in BC, Canada. Our Aquatic Center has a 25m Main pool with 150,000 gallons. This pool temp is kept at 83 degees with CL2 @ 1.2 ppm. Leisure pool with vortex, tots pool and couple other fun features. The temp kept around 93 degrees, with CL2 level about 3ppm. We have 2 so called Hot Tubs. The Upper tub is 525 gallons and hold approx 6-7 customers. The Lower is 750 gallons and will hold 8-10 customers at one time. We also offer a dry sauna which is our hot spot normally. This facility is 21 years old.
Cheers
Shawn

Re: Keeping TA up in small tub

Postby CanadianPoolGuy » Fri 13 Oct, 2017 07:27

My TA drops quite quickly in these small tubs. The acid kills my TA slowly as it brings my ph down. PH stays at 7.5 until my TA gets low than my PH starts to drop. By low I mean 30-40ppm. Were talking over 3-5 hours depending on bather load.
Denniswiseman
Swimming Pool Superstar
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Posts: 996
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Keeping TA up in small tub

Postby Denniswiseman » Fri 13 Oct, 2017 09:56

Are these hot tubs aerated as this will increase pH with no effect on the TA
So if you are lowering your pH with acid because of the aerating making it rise, you are also lowering your TA
You are then raising your TA with bicarbonate of soda
It's a bit of a vicious circle
You could try posting on this Forum as there may be more knowledgeable people who may be able to offer an alternative

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