Pool vs. Hot Tub Chemistry

[MisterMister]

Ok, I'm not sure if this thread in under the correct topic of not. If not, please move it. The Hot Tub thread didn't appear to get much activity.
(Moved to the Hot tub/Spa area. JasonLion)

My question, is there that much or any real difference between pool chemistry and hot tub chemistry?

I am enjoying so much what I've learned on pool chemistry, knowing that my hot tub chemistry has probably be more screwed up than my pool chemistry was. To further illustrate, I'm not sure of the size (gallons) of my hot tub. I will do some research on that. I do know it was the largest by volume of the ones sold at Rec Warehouse. Thinking 850g, but not sure enough to base chemicals on it. I've been maintaining it for the past few years with Bacqua Spa stuff that they sell, even though I buy it much cheaper elsewhere, and with the routine the installer provided me. I know it's out of wack due to the white flakes (clumps) in the bottom. And I know it's out of wack because you can't do proper chemistry by routine along.

And again, THANKS for all of the wonder information provided here.

Thanks,
Mister Mister

 

[JasonLion]

There are some differences but they are mostly minor. The largest difference is that chlorine gets used up more quickly at higher temperatures, so you need to add chlorine more frequently. Because of this many people use bromine for their hot tubs instead of chlorine. Chlorine works well enough, it is just that bromine is less effort to maintain.

 

[MisterMister]

With me being a very new user (almost) of the Pool Pilot, what do you think of the Spa Pilot? It's that convenience thing again. I really don't have the time for the daily hot tub maintenance.

With the Spa Pilot, it speaks of adding the starter blend after the water is balanced. What constitutes balanced?

 

[JasonLion]

You balance the water for a spa much as you would for a pool, except you use calcium even without plaster and you pay more attention for CO2 outgassing, which happens quickly when the jets are on.

The Spa Pilot Manual suggests the following levels:

1) Free Available Chlorine = 3.0 - 5.0 ppm
2) Calcium Hardness 150 - 200 ppm
3) Total Alkalinity 80 - 120 ppm
4) Cyanuric Acid 30-100 ppm (Outdoor only)
5) Salt Residual 1800-2200 ppm
6) Langelier's Index (water balance)+0.3 or -0.3
7) pH 7.2-7.8

Which is more or less what I would suggest, except that the FC level needs to be adjusted depending on the CYA level, I would use CYA of 20 indoors, I would keep the TA at 60-80, and Langelier's Index can go more negative if there isn't any plaster involved.

 

[MisterMister]

Ok, I've ordered the Spa Pilot, decide to give it a go. I'll let you know how it turns out.

 

[Guest]

Actually because of the smaller water to bather ratio in a hot tub it does change water maintenance somewhat. A hot tub is NOT a very small pool but a whole different animal.

 

[ChrisL]

After having a spa for about 6 months, I tend to agree with Waterbear. The chlorine residual will sometimes stay for three or four days, but at other times drop to 0 with no apparent reason and no one using the spa. The ph swings more frequently. The alkalinity also drops at unpredicable intervals. The water once clouded up when the numbers were EXACTLY the same as they were when the water was perfect. It took several days of shock level chlorine and then a good dose of non-chlorine shock to clear it up. After almost never having any combined chlorine in the pool, I had to learn to ignore amounts less than 1.0 ppm in the spa.

I can figure out when I need to test the pool and use the quick oto test most of the time. I test the spa for chlorine and ph with the dpd kit every day. (This is good news for Duraleigh as I will be ordering another chlorine test soon, even though I ordered the last one this winter)