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Thread: drop in salt water generator in small hot tub

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    drop in salt water generator in small hot tub

    Hi All! Any advice you folks have to offer on this subject is much appreciated!

    We have an older (made in the mid 90's) hot tub that holds 180-200 gallons in our basement. It has an ozone system but it has been unplugged since we bought the house both because of the fire hazard it presents and because the hot tub is switched on and off by an external timer to save electricity so it would not go on at the specified time. Because it is in the basement sunlight and algae are not problems but chlorine and other funky smells are...

    In previous years I have tried bromine as the sterilizer and have never been able to maintain a reasonable bromine balance for more than a few days. If I left the floater in the bromine would be unacceptably high after a day or two (even if I left the floater entirely "closed"). If I took the floater out of the tub for a day or two to fix the high bromine the concentration would drop like a rock. This would of course cause the water to become a nasty bacteria stew and I would need to dump and refill.

    The last season that I ran the hot tub I tried the "clearwater blue" copper ion system, again with mixed results. The copper concentration kept dropping to ineffective sterilization levels after a week or two (where was the copper going???) resulting in bacteria stew and a repetition of the dump & refill exercise. After 2-3 months of that argument I dumped the tub and have had it off / out of use for a couple of years in frustration.

    I am thinking of trying a "drop in" saltwater generator. The options I am eyeing are the Solaxx Saltron Mini (available for around $150) or the Nexa Chlor (which goes for around $200). Does anybody out there have experience with either of these SWG's in a small hot tub?

    The Solaxx Santron Mini looks more sophisticated (it has a control panel and tells you if salt concentration is OK) but I am concerned that it will make too much chlorine. It claims to work with up to 2000 gallon tubs and is only adjustable in hour increments of 1 to 10 hours of generation per day.

    If I understand correctly the Nexa Chlor can be plugged into a standard digital timer allowing adjustments as small one minute per day in run time. I dislike paying more for something less sophisticated but given the small system size and experiences with runaway sterilizer levels I think it might be the better choice. Could you please let me know if there other drop in systems out there that allow fine scale adjustments?

    How noticeable are the chlorine smells from a properly regulated SWG hot tub?

    Also - in an indoor hot tub such as this is it beneficial to have CYA or is it only useful in pools / hot tubs that are exposed to sunlight?

    In case it makes a difference the fill water is city water that is hard and quite alkaline as measured by a Taylor test kit. I can test a sample and give you numbers if it would help.

    -A Yeti

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    Mod Squad JVTrain's Avatar
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    Re: drop in salt water generator in small hot tub

    I've heard great reviews from other users here on TFP on the ControlOMatic brand chlorinators. See the website here: Salt water hot tub Chlorine Generators makes chlorine out of salt There are several options available.

    Even though you have an indoor tub, you still want CYA in the tub to moderate the strength of the hypochlorite, keeping it from being too harsh at manageable FC levels. I'm not sure if the manufacturer of any of these products recommends a specified level of CYA, but 20-30 ppm is a good number to use for any spa whether indoors or out.

    Your city water's calcium hardness (CH) probably won't change things much, but may contribute to scaling of the salt water chlorine generating cell if pH is allowed to be high in the spa. On a pH note, if your alkalinity is high, you'll have fast pH rise especially in a hot tub with lots of aeration. A good TA number for spas is 50-60 ppm. Lowering TA is simply a process of adding acid to bring the pH down to 7.0 then aerating to raise pH again. Repeat until pH is stable.

    Even though you're looking at a salt water sanitation method, check out the sticky on using chlorine in a spa: How do I use Chlorine in my Spa (or pool)?) All the levels and recommendations still apply to a SWG situation in a spa. Borates mentioned in this sticky are helpful (for some pH stabilization and some anti-algal action) but not required, in my opinion.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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    Re: drop in salt water generator in small hot tub

    I installed the controlomatic chlormaker il in my hot tub a couple months ago. After ChemGeek helped with my chemistry (too much cya), all I have done is added a couple ounces of muriatic acid to lower pH. I wish I would have done this years ago!

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    Re: drop in salt water generator in small hot tub

    Thank you JVTrain and Pilotwerx for the pointer towards the ControlOMatic line - it looks and sounds quite promising. Especially the SmarterChlor product that claims to measure the chlorine level and then determine whether to run or not. Since I will sometimes be ignoring the the spa for a week or so the self monitoring aspect would be very nice. I notice that it seems to be a new product offering, does anybody here have experience with it? I assume the cell contains some sort of ORP / PH sensor combination.

    So it sounds like I want to make sure to get TA down to 50-60 ppm and 20-30 ppm CYA then start experimenting with the SWG settings to get a stable free chlorine level?

    I have seen the chlorine article before but it was good to review it.

    Even with the "boost" button I have a feeling we're going to have to add bleach after soaks because of the very small system size.

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    JoyfulNoise's Avatar
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    Re: drop in salt water generator in small hot tub

    Since it sounds like you have had some nasty bacteria soups in that tub, I would definitely do a deep clean of the tub with Ahh-Some. I am willing to bet your tub plumbing and components probably have had some nasty biofilms develop in them. After a good deep clean, then you can switch it to salt.

    Question/suggestion - check the heater and other metal components first before going full salt. You'll want to make sure they're compatible with saline water.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: drop in salt water generator in small hot tub

    The controlomatic runs at 1800ppm so it shouldn't hurt any components. Curious to see how the smarterchlor works out. Measuring chlorine levels on the fly is not easy.

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    Re: drop in salt water generator in small hot tub

    JoyfunNoise - I agree it could probably benefit from a through cleaning - thank you for the link. In addition I seem recall seeing an article on how to thoroughly clean a spa (for example when you buy a used one you don't know the history of) but can't seem to find it anymore, if somebody knows perhaps they could post a link.

    Honestly I'm not too concerned about this hot tub's components because it is so old - if I do in a heater element or the wet side of the pump it was probably about time for a new one anyway. I think the tub manufacturer is long gone although I have gotten some minimal help in the past from Balboa who manufactured the control / heater unit.

    Pilotwerx - Yes I was reading up on ORP control systems on this forum earlier today, I definitely want to ask some questions before plunging in for the smarterchlor.

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    drop in salt water generator in small hot tub

    I have had the Chloromatic in my hot tub for over three years, I would never be without it. Makes maintenance simple. Whenever it goes out, I will immediately buy another. Here is what I keep things at. Once balanced, is virtually maintenance-free.

    temp 104
    CYA = 30
    CH = 350
    TA = 60
    Borates = 30
    PH = 7.5
    Keeps FC at 2 PPM On setting 4
    All I have to do is add a little dry acid now and then to keep the pH in check. I probably address it maybe once every 10 days. Simple crystal clear water.


    ~14K gallon - AquaRite AQR15 SWG - pool Newly plastered on April 9 2016
    TF100 kit - STA-RITE SYSTEM3 Modular Media Filtration - Model S8M150
    Pool water supply from on site water well = CH of ~350 and TA of ~350
    Doheny's Discovery Automatic Robotic Cleaner/Pentair Model 011018 VS Pump
    Sundance Altamar Hot tub separate from pool / central Oklahoma

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