Salt Water Chlorine Generators: Cost-Benefit Analysis?

[VWAffe]

I'm about to resurrect a 2001 Mountain Spring Spas ~400 gal 7-man tub. It's in good shape except for some jet internals and needing some TLC - but this is my first hot tub and I'm on the fence regarding using bromine or chlorine.

I'm leaning towards a chlorine-based system for overall cost, cleaner feel, and for a longer-lasting fill, but would like to use a salt-water-based chlorine generator to reduce the demand for a daily water maintenance regimen.

I'd be using a drop-in generator as our tub doesn't have a 24-hr circulation pump. What's the life expectancy of a typical chlorine generator cell and how does the cost of pool salt and the cell compare to the cost of using only dichlor/bleach for the same length of time? I'm willing to pay some for convenience, but don't want to break the bank.

(I'm looking at the Solaxx system - gets good reviews and is the cheapest at $180 for the controller and first cell, and replacement cells are $100.)

I honestly have no idea how often we (1-4 of us) will use the tub, but it may be as few as one to a few times a week.

Also... the tub is equipped with a (certainly-defunct) ozone generator... if I used bromine, I'd certainly replace it, but is it a good idea to use it with chlorine? If I read correctly, it not only oxidizes contaminants, but also chlorine... so I assume that if it's a good idea to use it to oxidize contaminants, it would run less often in a chlorine-based system than in a bromine-based tub (where it does double-duty to create bromine from the sodium bromide reserve in the water)

Thanks!!

[njmurvin]

I will be watching this thread as I am in a similar situation (although my spa is newer). I have a Marquis spa and it also does not have a 24hr circ pump. I have been using the 3 step Bromine method and it's good for keeping the bromine levels up with less frequent monitoring. But, when I remove the cover, even standing near the spa, I start coughing. There is definitely some kind of chemical buildup that occurs under the cover over time as this doesn't happen for a while after a refill. I monitor the chemicals and everything appears in order. I'm interesting in trying the chlorine generator to see if it lessens this effect.

With regard to the ozone generator. I have one as well. But, without 24hr circ, it doesn't do much. It only runs when your pump is running and mine only runs about 2-4hrs per day. Personally, I will not replace mine when it dies.

[chem geek]

When using chlorine, an ozonator only makes sense if you use the spa every day or two because with that higher bather load the ozone will oxidize some of the bather waste so that chlorine doesn't have to. The problem is if your bather load is lighter so that you use the spa only on weekends or with gaps of a few days in between soaks. In that situation, ozone reacts with chlorine (producing chloride and chlorate) so increases chlorine demand in between soaks requiring you to add chlorine every day or two. Without an ozonator, you can usually add chlorine twice a week and be fine and even add it once at a higher level to last the week when on vacation, especially if the water temperature is lowered.

As for a saltwater chlorine generator, there are several people using the ControlOMatic Technichlor and are happy with it. The price is around $220. I don't know about other brands.

Just keep in mind a few things. These generators are NOT automatic in the sense that they don't know when you're soaking so don't know how much chlorine is needed. You set them at a level to maintain a chlorine level in between soaks. Some have "boost" mode but this may be too little or too much for your bather load. You can just add bleach after each soak to handle your bather load and use the saltwater chorine generator to maintain chlorine levels in between soaks. That will work out best when using the spa less frequently and will have the salt cell last a long time.

Note that you MUST add Cyanuric Acid to the spa water or else the active chlorine (hypochlorous acid) level will be far too high. You can do this either by adding pure CYA (which dissolves slowly) or by using Dichlor initially for a while -- roughly 33-44 ppm FC cumulatively added gets you 30-40 ppm CYA. You'll need to use Dichlor for a day a month to add around 5 ppm CYA since chlorine slowly oxidizes it. If you do not use CYA, your hot tub equipment and covers will not last as long and your swimsuits and skin will be oxidized faster and you'll smell more chlorine (i.e. it will outgas more).

[PreservedSwine]

180 buck buys ALOT of chlorine. I doubt you'll save any money, a spa is not like a swimming pool with a constant chlorine demand. You'll likely need perhaps a teaspoon or so per day of chlorine at the most. The salt system is for convenience, assuming your chlorine demand will be constant. If your chlorine demand is not constant, a salt water chlorine generator is not a good fit. You'll spend more time trying to dial in the correct setting than just tossing in the chlorine manually. And in the process potentially cause hundreds of dollars of water chemistry damage.

[VWAffe]

Thanks for the replies. I've read the threads on the 2&3-step bromine and the dichlor/bleach method. Since it promises to be the cheapest overall, I'll probably start with the dichlor/bleach method and see how it goes. If it turns out to be too fussy, I can always add a salt cell to the mix to lower the maintenance demand. I honestly have no idea how often we'll use it... it may get a lot of use or very little once the novelty wears off.

If I do add a chlorine generator, it would be to do exactly what you describe - maintain a background chlorine level to lessen the daily maintenance demands when the tub isn't in use. I'd already figured out that a salt cell generator will not replace the need to manually bump chlorine after a soak.

I like the summary of when an ozone generator would be useful in a chlorine system... based on your info, it only seems worth it to replace it if we end up being heavy spa users. I think I understand correctly that with a chlorine system, a salt cell and ozone generator could be used together, but each one has an ideal application, and times each wouldn't be advantageous. I'll start simple!

Cheers,

Nate

[chem geek]

Basically, if you soak regularly then the saltwater chlorine generator isn't very helpful. It's best for those who just soak on the weekends and for those who soak infrequently and have ozonators. It's just about automatic dosing in between soaks so look at it that way in terms of price for convenience.

[mrwrick]

This is an old topic without activity,. so I hope I resurrect it.

I have a bromine spa that sits idle for weeks at a time at my vacation home with 24 hr. recirc pump that keeps my ozonator running full time. I add chlorine bleach when I arrive and after a couple uses and when I leave. I keep temp down in 80's when not there. My water is clear, TA is around 120 but pH is over 8. I assume that us because of high TA. 

My question is this: Since I only use chlorine in my 24/hr. ozonated bromine spa when I shock the tub do I need CYA? I have never added it since i replaced my jet pump and refilled the tub this summer.

My other questions is this: Since my tub is used infrequently am I better off with a bromine and ozone sanitizing system or a salt chlorine generator and ozone system? I understand if using chlorine as primary sanitizer I need CYA.

Thanks as always to the wizards of the Forum.

[MPurcell]

In a bromine spa you don't need to use cya. If you established a proper bromide bank by adding sodium bromide each time you filled the tub, then the chlorine you add is almost instantly converted to bromine.

You could bring the TA and pH down with muriatic acid. A pH of over 8 is not good for either water quality or equipment longevity. Ideally, pH should be between 7.2 and 7.8, and certainly no higher than 8.0. You could find the TA level that will keep pH stable and in range. Typically, that would be somewhere between 50 ppm and 80 ppm in most tubs, as long as you are not using bromine tabs or MPS.

Bromine and chlorine both work well. I think it is a personal decision. A lot of people prefer chlorine for less smell and better feel. I have no experience with SWCG's or keeping the chlorine level up for several weeks while the tub is not in use, however, so I really can't comment. One thing is for sure, whether you use chlorine or bromine, you don't want to let the sanitizer level fall to zero, or even below the minimum effective level at any time while the tub is idle.

[B Thermophile]

My experience:

Usage: self and wife 1-3 times per week with occasional 1-2 week lapses. Once per 6 months we have a visitor or two use it.

equipment: 2004 Marquis Euphoria, 400 gallon, Balboa M7 heater, AquaSun xl50 ozone gen, Saltron mini SWCG add-on (1-14-2015), 

water goals according to my log: CH 200, Total Cl 5, Free Cl 2, PH 7.4, T. Alk: 90, CYA: 50, Salt: 2200-3000ppm

Average results with minimal attention last 12 months: CH: 175, Cl: 3, PH: 7.2, T. Alk: 50, CYA: low to none, Salt: 2800-3k

Generally I've followed Nitro's Dichlor bleach method for start-up. Also use the bleach decon method at water changes (6-9 moths).

I almost exclusively use only Dichlor for shock etc these days (hoping to boost CYA).

SWCG Results: 

Pros: Daily water tests not needed. Weekly or less seems enough. Generator maintains chlorine levels very well set at 7 hours per 24. With normal weekly usage. Only periodically do I need to use Dichlor (shock, or higher usage periods). Water stays clean for 6-9 months. Spa is as close as I've been to carefree from a water maintenance stand point. If you don't use the spa chlorine levels rise (self shock), just unplug the SWG if Cl is too high. Electrode cell lasted until 5-2018 (2 -1/2 years with 1 or 2 cleanings).

Cons: higher maintenance: replaced heater element due to GFCI trip 10-12-16, Replaced entire heater tube assembly again in 5-7-17 due to GFCI tripping and seepage from sensor ports and heater terminal penetrations. Corrosion visible. GFCI trips again 12-15-18. Upon inspection: heavy corrosion on and around heater element including pitting. Once again seepage at penetrations (this was an after-market factory unit not assembled by me).  Corrosion (minor) visible on heater tube as well. Minor Rust staining visible on adjacent pvc fittings. Some mild staining? Has become visible to the spa siding (plastic) over time the SWG has been in use (fumes?).

Conclusions: SWG retrofit can decrease the frequency of your need to attend to water maintenance (I've gone 2+ weeks). The disadvantage is I have seen the heater become an 18 month replacement item!

corrosion to the heater is not the only issue to consider. All other metal parts in the spa can be expected to corrode more quickly as well (e.g.pump shafts, pump seal wetted parts, cover lift hardware). And yes stainless steel DOES corrode. (I believe I bought the titanium replacement element but I couldn't get it to seal in the old tube).

i have not seen problems with my pumps yet (one is original, one was replaced in 6-9-17 due to unrelated electrical issues).

I am a professional tradesman with extensive experience with mechanics and plumbing and can self-perform maintenance and repair tasks. If that were not the case the costs to deal with these issues would be prohibitive.

I am curious about implementing a sacrificial anode to minimize the attack on my heater components. I am also interested in mounting the M7 sensors in the adjacent pvc fittings to minimize penetrations in the heater tube. Corrosion particularly attacks the weld and thread zones on the SS tube.

Any ideas?

I am interested in your feedback on all of the above including my conclusions.

Best!