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Thinking About Switching From Nitro / Chemgeek Method - Input?


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For the past few years I've been using the Nitro / Chemgeek sani method for my hot tub with good success. It works well if followed, and although a bit labor intensive at times it results in excellent quality of water.

However the past few months I've been traveling a lot for work, and my water quality has suffered as a result. I'm simply not around all the time to continually monitor and treat the water - and being gone 7 days at a time with this method is tougher.

I'm considering changing to a different method - and curious if anyone could give me some input? Our goal is to use as little chemicals as possible - my wife has asthma and some chemical sensitivites, and we have 2 small children who sometimes 'drink' the water even though we tell them not to. Hot tub has a working ozonator, and is a bullfrog 420 gallon unit.

  • I've read waterbear's bromine 3 step process and that looks intriguing. However, every time we've sat in a bromine hot tub we have noticed strong chemical odors and a lingering odor on our skin. Is this typical of a bromine method, or were those people doing it wrong? We have very little odor at all with the nitro method.
  • Alternatively we've considered the nature 2 method - combining it with the nitro we currently use, hoping it might extend the service intervals. Friends who have tried it have seen the water get cloudy very quickly, although I don't know how strict they were with their sanitation. Does it offer any improvements over the method we are currently using?
  • Lastly we have considered a SWCG, likely the techniclor, but Bullfrog tells us they will not warranty the tub if we use one of these. I'm assuming that is because of corrosion?

Thanks for any input you can give!

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I was going to suggest bromine since you can use bromine tabs in a floating feeder to dose when you are not there. However, you are right that bromine smells different than chlorine and some people don't like it. If you add oxidizer after your soak, then you can maintain a low 2-4 ppm bromine level in between soaks which is roughly equivalent to 1-2 ppm chlorine so when you start your soak you won't have too much bromine. Some people try to use tabs only and therefore have a high enough bromine level to handle their bather load, but that means a higher level during the soak which can be annoying. So you could try this in a better way with a low bromine level in between soaks so you start out low. If you have an ozonator, then it will make bromine from the bromide bank which means you may not need to use bromine tabs, but it can be tricky to have the right-sized bromide bank to not underdose or overdose the bromine level.

As for Nature2 with silver ions and using MPS as the oxidizer (and disinfectant when used with the silver ions), it will last longer than chlorine if you dose with excess, but it still does get used up. So perhaps you could dose enough to last for a week, but probably not for too much longer. As for the water getting cloudy, you can mitigate that by using chlorine on occasion, say once every week or two. The main benefit with this method is that it is largely non-halogen so works for people who for whatever reason want no chlorine or bromine during their soak. As I wrote, the MPS does last longer than chlorine after bather load is handled, but probably not enough for an extended vacation. If you have an ozonator, the ozone won't react with MPS the way it does with chlorine.

An SWCG is a good option if one uses CYA in the water to moderate chlorine's strength. As for the warranty, yes the issue is corrosion, but again the main reason for such corrosion problems is that the SWCG is often used without CYA in the water which makes the chlorine WAY too strong so more corrosive especially combined with the higher salt level. Nevertheless, even with CYA in the water and careful setting of the SWCG to not get the FC too high, the higher salt level is more corrosive especially to inferior materials such as lower quality metals (e.g. zinc). The salt level for the Technichlor is around 2000 ppm, not the 3000 ppm typically used in swimming pools. If your spa has decent stainless steel (at least 304 if not 316 or 316L) and has a cupro-nickel or titanium heat exchanger, then it should not have any problems with the higher salt level.

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  • 3 months later...

Chemgeek, thank you for the reply! For some reason I never got a notification you replied - sorry about the long response time.

In the case of Bromine, is it possible to get a very low level of active oxidizer in the water as is done with the Nitro method and CYA? As I mentioned we have some concerns about keeping the oxidizer load as low as possible in the tub when soaking. Using the non-halogen of Nature2 is appealing in that manner.

Interesting point about the Ozonator. So the ozone will not use up MPS as it does with Chlorine? It's tough to keep chlorine in our tub at all times due to the rapid depletion by Ozone.

Bullfrog has vacillated on the use of a SWCG, but they remain steadfast in that it will void the warranty, but not necessarily cause damage depending on the salt level in the water. I'll ask them a bit more about the materials used in the tub to verify the safety. Is 2000ppm considered a high level of salt? I'm curious what our level would be after a few months of using bleach and if we are already at that level.

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With bromine you can try and start your soak with a lower level and then add an oxidizer after your soak proportional to your bather load. You would then tune your bromine tab output to be at a lower level you can tolerate for the start of your soak, but that will be roughly 2-4 ppm Bromine you'll need to do to maintain disinfection in between soaks and at that level (which is roughly similar to 1-2 ppm chlorine) you may still notice the bromine too much.

And yes, the Nature2/MPS approach would avoid having any haologen (chlorine or bromine) during your soak though usually with that system you still need to use chlorine once every week or so to keep the water clear. Ozone will not deplete MPS the way it does with chlorine (and as you know ozone will create more bromine from a bromide bank).

As for the saltwater chlorine generator, I think the key is to make sure you maintain CYA in the water, say at 30-40 ppm or so. That will significantly moderate chlorine's strength which will help reduce corrosion rates. The higher salt level does increase corrosion rates, but we haven't heard of any such issues if people also have CYA in the water. With no CYA in the water, the active chlorine level will be high and that may be what the manufacturer is worried about (well, they probably don't understand the FC/CYA relationship).

Using bleach, for every 10 ppm FC you add around 17 ppm salt. One is usually able to go twice as long between water changes compared to the standard WRI formula so this would be a formula of (2/9) x (Spa Size in Gallons) / (# of Person-Hours per Day). If we assume a 350 gallon spa and 7 ppm FC (in 350 gallons) per person-hour needed to oxidize bather waste, then that is 78 days for 1 person-hour per day so at 7 ppm FC/day that's 546 ppm FC which would be around 930 ppm salt. So normally one doesn't get much above 1000 ppm salt when using bleach. Sometimes we hear about 1500 ppm if the water is changed as frequently, but 2000 would be unusual. Also, for a saltwater chlorine generator, the 2000 would be all the time whereas with bleach the average salt level would be even lower than the 1000-1500 peak.

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  • 3 weeks later...

Chemgeek, I sincerely appreciate your input. A few updates:

I've figured out I'm no longer under warranty - so voiding the warranty with a SWCG isn't much of a concern. I don't want to ruin any components in the hot tub, but it sounds like if I keep the CYA 30-40 and salt at a decent level I will likely be fine.

Your math breakdown for the salt level is much appreciated. I can typically go 90-120 days between water changes as long as I stay on top of it. It's a 440 gallon spa, so if I math is correct we are getting up in the 1200-1400ppm level of salt already. Your point about the average is well noted. Is there anything specific I should ask Bullfrog about - composition of the heater element, etc, prior to making the leap into SWCG?

Last question, and likely the dumbest. Is there a recommended brand of SWCG, and how does one wire these in? Can they wire in the control panel, or does one need a GFCI 110V edison outlet by the tub? The Technichlor seems to have good reviews, but I've looked all over their website and they have no contact email or phone - which gives me pause should I need some sort of support. It also seems to be out of stock from Amazon and everywhere else - leading me to believe they have gone out of business or are in a refresh cycle.

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You can ask if the heat exchanger is copper, cupro-zinc, or titanium.

Don't know what's going on with Technichlor. People did like them, but strange they are out of stock everywhere and that you can't contact them.

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