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Thread: Indoor Hot Tub

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    Indoor Hot Tub

    I am getting ready to fill my indoor hot tub and was wondering what the CYA level should be. What are the recommended levels and rank of importance of CYA, calcium hardness, TA, pH, FC and CC?

    I will probably pump water from the pool directly to fill the hot tub.

    Where are the water balancing procedures located for SPAs and Hot Tubs in case I decide to use tap water for the filling operation?
    In-ground concrete/vinyl 21000 g, sand filter, Pentair 1 HP and 50 gpm. Pentair Legend in-pool cleaner, Nature 2 system (cartridge removed).

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    Join Date
    Jan 2009
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    Re: Indoor Hot Tub

    What I think is the best spa summary is here.

    In an indoor or covered spa, CYA is not really protected the chlorine from sunlight. But, it is still acting as a chlorine "reservoir" and makes it easier to maintain a reasonable FC level.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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    Re: Indoor Hot Tub

    I had read the article by Nitro previously and could not locate it. His approach is what I will use except I will pump water from the pool to the hot tub. Since there are presently no borates in the pool should I first bring the borate level to 50 ppm and then balance water? If for some reason I elect to fill the hot tub directly from the tap (municipal water), at what point in the balance procedure should I bring the borates to 50?
    In-ground concrete/vinyl 21000 g, sand filter, Pentair 1 HP and 50 gpm. Pentair Legend in-pool cleaner, Nature 2 system (cartridge removed).

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    Laenini's Avatar
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    Aug 2008
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    Brooklyn Center, MN
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    Re: Indoor Hot Tub

    I'm a spa newbie myself, and only slightly more experienced in pool care. We put up our pool last summer and then this summer we added the hottub. When the tub was delivered in July, the installers saw our pool with its beautiful, glistening, crystal clear BBB water and decided to pump pool water over to the hot tub to fill it rather than use the tap water. While it seemed like a good idea at the time, I now have some doubts. The first month the tub was up and running with that pool water in it, I just couldn't seem to get the hang of maintaining proper water balance and sanitizer levels in the hot tub. Levels kept fluctuating on me and I couldn't seem to predict how the tub was going to behave. I also noticed the jets and venturis started gumming up and sticking. Many of them I couldn't operate at all anymore. I was starting to think that maintaining a spa was beyond me! It never occured to me though that the problem may have been in the water I started with. At the end of August I decided to do a complete water change, mostly because I wanted to do it for the first time while the weather was nice outside, plus I was a little bored one day to boot. So I drained the tub and refilled it, this time using tap water. I balanced the pH, and TA and put my bromine starter and floater in. Since that water change, I have had none of the chemistry problems I had noticed the first time around! The pH has been much more stable, the sanitizer level has been much easier to keep up, and the gummy jets and venturis have been functioning much better once again!

    I'm not sure why my pool water didn't work out so well in my spa. While I have been using BBB this year to maintain my pool, last year I used traditional pool store chemicals. So there may have been some residual chemicals still left behind in the pool water that were not so good for the spa. Also, I have added NaCl to my pool water to improve the "feel" of the water. I wonder if the salt was contributing to problems in the spa too. Whatever the reason was though, I don't think I will ever fill the spa from the pool again.

    Good luck with your new spa, Rocky! Maybe filling your spa from your pool won't cause you any problems, but I thought I would share my experience just in case.
    Leanne
    Pool: 24' round by 48" deep AGP
    Waterway 1HP-2 speed pump, H100 Heater, sand filter, skimmer, using BBB (love it!)
    Hot tub: 2008 CalSpas, 8x8, 8 seats, 60+ jets, ozonator
    3 step bromine sanitation

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    Join Date
    Mar 2007
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    San Rafael, CA USA
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    Re: Indoor Hot Tub

    The first fill of a new hot tub isn't going to have the water last as long regardless of the method used. A new hot tub has chemicals on surfaces that will affect water quality. Plan on doing a drain/refill of a new tub in a month or two regardless of the sanitation method or source water that you use.

    Pool water is OK to use if it was properly maintained without a lot of extra chemicals, but if the Cyanuric Acid (CYA) is high in the pool (especially above 50 ppm), then I wouldn't recommend using such water. It's better to have around 30 ppm CYA in the tub and not more than 50 in order to get decent sanitation against the bacteria that causes hot tub itch. Also, if the pool has exposed plaster/gunite/grout or otherwise has the Calcium Hardness (CH) be much above 150 ppm, then that may be too high for the spa. The higher spa temperatures usually need a lower CH level.

    Since the spa volume is relatively small, it's usually best to start out with tap water for the freshest, cleanest water that will last the longest.
    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: Indoor Hot Tub

    Regarding at what point to add borates, you could do it anytime after you have the pH where you want it. If you measure the borax and acid correctly, or use boric acid, there should be little net effect on the pH.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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