2 questions

[anne]

1. Does adding calcium generally affect pH or TA? I have never had to add Ca before, but tonight after doing so, the pH is suddenly 7.9-8.0. It was rocky-steady at 7.4 for the last two weeks. TA was 90, is still 90.

2. There is probably no one right answer to this one, but I'm looking for opinions: So since my pH jumped to 8ish, I need to lower it. I'm at 2 weeks post-refill, so I could argue that it is time to shock, but my CC is under 0.5. I could add MPS, and get the pH down and shock with one step, or I could argue that shocking is not needed yet, and just use liquid acid to decrease the pH. Will one have less effect on TA than the other?

[windsurfdog]

Though I have been and continue to be a proponent of using unbuffered MPS to both shock and lower pH, I think a major consideration is the contribution to TDS that is attributed to MPS.  If you needed to shock, then using MPS would be the best solution.  If you didn't need to shock but wanted to adjust pH, then I would choose dry acid over MPS.  Dry acid will not contribute to TDS as much as MPS.

BTW, what was your CH reading before adding the calcium carbonate to raise CH?

[Tman122]

1. Does adding calcium generally affect pH or TA? I have never had to add Ca before, but tonight after doing so, the pH is suddenly 7.9-8.0. It was rocky-steady at 7.4 for the last two weeks. TA was 90, is still 90.

2. There is probably no one right answer to this one, but I'm looking for opinions: So since my pH jumped to 8ish, I need to lower it. I'm at 2 weeks post-refill, so I could argue that it is time to shock, but my CC is under 0.5. I could add MPS, and get the pH down and shock with one step, or I could argue that shocking is not needed yet, and just use liquid acid to decrease the pH. Will one have less effect on TA than the other?

How long of a time span between adding Calcium and testing the PH. You may want to wait a few days and re-check. If you have never added calcium before, may I ask why you did now? There's not a whole lot of material in a Modern Spa that facilitates precipitaion of calcium. In fact I'm not sure there is anything. I may be missing something here but i always though calcium was added to prevent precipitaion of calcium from concrete like surfaces.

[hottubdan]

I have not heard of Calcium effecting pH.

Anne, why did you have to add Calcium.  With your water, you should not have to.  

I would not be concerned with your pH.  Adding dichlor, which I think you use, will drive pH down.

I have always been a proponent of weekly oxidizing to oxidize contaminates out of the water, not only to free combined chlorine.

[anne]

I am as puzzled as you why I now need to add Ca. I have always before had hard water (500-600 ppm). Just for fun, I checked my Ca at this most recent fill, and it was only 70! I double checked it and checked the tap water: 70.

So I added 1 1/2 cups (what I calculated as needed to bring it up 100ppm) and now it is happily at 170. I checked the pH about an hour after adding the Ca (same time that I checked the Ca)

My pH this morning is 7.7 (was 7.9), so I'm just going to leave it all alone for now. I have a call into the "water works" of my city to ask about water supply.

[hottubdan]

Anne,

I can't recall where you live.

However, I was just talking to a customer in Woodland.  He told me the west side of town now has water that is softer than the rest of the city.  He is on his 3rd spa (all HS he has moved 3 times) 2nd in Woodland, and was also surprised with how much softer his water is in his new house.

As a spa veteran, he uses ozone, mps, Enhanced shock, pool test kit (could not remember brand).

Dan

[anne]

Dan, thanks for the input.

I have an amusing, if not pathetic story for you, and I guess I'll share it with everyone: Since I work sort of near your Elk Grove store, I stopped in yesterday for calcium. The gentleman there recognized me from when I was spa shopping (at the Roseville store). He assumed that I had purchased a HS, and I didn't have the heart to tell him otherwise. I just didn't say anything. Then at checkout, he gave me the 10% customer discount ($0.79) on the calcium, and I was too embarrassed to correct him. It was so silly. So I owe you guys $0.79. I honestly felt guilty all day. Cup of coffee on me one of these days!