Can't Seem To Get Ta To Come Down

[nymtnbiker]

Been lurking here for a while as I have had concerns about a friend's spa that I delivered and wired in for him bout a year ago. I'm house sitting for them watching their dogs, chickens, cats ect, and wanted to do a fresh fill of water in his spa. To be blunt, he has never filled this thing up right and started with a bromine reserve, even after I have told him numerous times how simple it is. He usually would end up using tons of defoamer, and almost every time I'd be out here the water would test out at nearly 0ppm of bromine. His answer was throw a shock in it and call it good, and refill the water every 2 months or so when it would start to smell odd even after a shock. His wife finally agreed with me to pickup the stuff needed to set this up right, and she's ordering the Taylor K-2106 kit when they get back, so for now I have to rely on test strips.

They are on well water, and I couldn't find a "spa stick" attachment locally, so I am pretty sure their water is quite high on the CH scale, unfortunately the strips I have don't measure the CH, but I have to believe it is pretty high. They do have a chlorine-filter injector system on their well, that injects a bit of chlorine water into the incoming stream and runs it thru a large blue filter unit, which I believe is there to reduce/remove sulfur and possibly iron, though again he never maintains that system either. I wonder how hard it really is to add a gallon of bleach to the 15gallons of water every 3 weeks, but obviously it's too much work for him. So I have that system setup right and I don't taste any chlorine or off flavors in their water, but even with that working I added 2.5oz of metal/anti scale stuff to the fresh fill of the spa.

I spent 3 hours draining, cleaning, rinsing, and scrubbing the scale from the inside of the tub, and rinsing again (yeah they had scaly buildup from what they believed was a blocked filter, but I tried to explain it was their hard water, course I had no idea what I was talking about).

Spa is 385 gallons, and I was following the bromine for beginners thread exactly except for the metal/anti-scale stuff and that I filled the tub from his hot water washing machine connection. He's got a great natural gas furnace that was giving 95F water to fill the tub all the way up to the "full level". I tested the TA and the PH after running the jets for 5 min just to make sure the water was mixed at an even temp, and that the metal/anti scale stuff was well mixed in. I got TA of over 360 (the highest the strips I have go), and a PH of 8-8.2. So following what I read I picked up 1qt of muriatic acid (31.45% 20 Baume), and hoped to bring the TA down to the reasonable 80-130ppm and the PH down to around 7.4 or so.

I have now added 3oz of acid and ran the jets for 1 hour. I got TONS of foam, and not the kind that goes away when the jets are off, I tested the water, still had TA of 360+ and the PH was right at 8. Recalculated my desired TA and PH in the pool calc with 385g water, shooting for 80ppm TA and 7.2 PH, added 4oz of acid, and let the spa run for 10 min, then did a test. The ph dropped to about 7.6 and the TA might have come down to 240ppm, but it was hard to tell for sure. I really wish i had the drops kit. Tested an hour later with running all the jets and the PH was back up a bit at 7.8, and the TA appeared to be at 360 again. 4 more oz of acid, and this time the PH dropped down to 7.2 after about 5 min of running, but the TA still seemed to be really high. Still getting some good amounts of foam, but I am hoping that once the water is balanced a bit and I shock it, that won't be an issue. Spa setup introduces ALOT of aeration to the water so I am pretty sure that part of the TA thing is on track.

Got another 20 min of running before I test the TA and PH again, but at this point I am concerned that I may be getting nowhere with fighting the TA, and that I am gonna need a lot more acid and time to get the TA down. I really want to use this thing as it's been killing me having it sit there and not jumping in for the past few days. My friend is due back in a few days and I wanted to have the perfect spa water setup before they got home. Anything I am doing wrong or obsessing over?

[chem geek]

I'm not sure where you got that 4 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) would lower the TA as much as you expect. 4 fluid ounces in 385 gallons would lower the TA by about 40 ppm so to 320. Basically, to get to 80 from 360 would require 27-1/2 fluid ounces, but not added all at once or else the pH would get too low. Anyway, you are somewhat shooting in the dark with test strips. You are, however, on the right track.

Once your TA is in better shape and the pH isn't getting so high you can see if that helps the foaming situation at all.

[nymtnbiker]

I plugged in my numbers at http://www.poolcalculator.com/ for 385gallons of water, 8.2ph target of 7.2ph, and 360 TA with a target of 80. I guess i am missing something cause it says 4.2 oz. I ended up getting the PH down to about 6.8 and aerated for a while till it came back to about 7.2, then did another 4oz of acid, and finally the TA was down to 120 and I called it good for the time being. Used borax to bring the PH back up to 7.6 and ran the tub for an hour or so with the cover off and it seemed to stay right on at 7.6 and what looks like around 120 TA (not really a fan of the test strips, I've used drops kits in the past on pools and find them much better, but I have to use what is available) tossed in 2 oz of dry sodium bromide, let that circulate for 30min, then poured in 10oz of bleach (was not listed on the bottle so I assumed it was 5.25%) to shock. This morning the bromine level tested at 6, ta looked the same at around 120, and the PH seemed to still be 7.6.

When my friend's get around to ordering a taylor test kit I'm gonna make sure they order one of those spa fill sticks, so that the next time the spa needs to be filled the water is a little more balanced right off the bat. Course what would have been really ideal would have been if I could have snagged a free water softening system for them that was on the local Craigslist last week, but I was 3rd on the list and I guess I missed out on it.

Time to go enjoy the spa again :-)

[nymtnbiker]

Oh yeah I forgot, soon as i did the starter of bromide and the chlorine "shock" of bleach there is no more foam at all. literally the foam/bubbles that form while using the spa disappear in 30 sec or so once the jets are off.

[chem geek]

The Pool Calculator will not calculate how much acid you need to lower the TA -- it only calculates how much you need to lower the pH. That's fine since you don't want it lower than 7.0 anyway, but it takes multiple cycles of acid addition with aeration to get the TA lower and the cumulative amount of acid you need to add will be much higher than what it takes to just lower the pH to 7.0. The rule is that it takes 25-1/2 fluid ounces of full-strength Muriatic Acid to lower the TA by 10 ppm in 10,000 gallons. So scaling that down for 385 gallons would be about 1 fluid ounce to lower the TA by 10 ppm which is consistent with what I wrote earlier (4 fluid ounces lowers the TA by about 40 ppm in 385 gallons).

I'm glad the foaming stopped. Must have been something that the oxidizer was able to take care of (either bromine or chlorine).