Managing CC's in Hot Tubs

jseyfert3

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I've started considering adding UV or replacing the ozone system in my spa to help manage CC's. I seem to have persistent CC's, and relatively speaking not a lot of use. With the cold winter temps the spa stays covered and with a floating bubble cover on the water to help reduce evaporation. I'm sure these don't help as there's not much breating, but with overcast skies in winter and a spa located on the north side of our house there's also not a lot of chance to open it to get UV from the sun.

Would UV be more effective than Ozone? I'm messing with my pumps and replacing valves in a week or two so modding in UV could be done with relative ease in the near future. The spa did come with Ozone but it's long dead. Easier to swap though. I've seen @JoyfulNoise mention that ozone can be good if it can be used after a soak to break down waste, before FC is added. I get the impression UV is better for breaking down CC's that are already formed as opposed to directly breaking down waste?

Would the use of MPS after soaking help break down waste and avoid CC buildup? If so, that seems like the best place to start, I can grab the Taylor MPS interference remover kit so I can test for FC/CC appropriately if I go this route.
 

JoyfulNoise

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Why don't you try to see if you can install some cheap UV lamps on the inside of your cover? Might be a cheap and easy experiment to do rather than modifying your plumbing. Obviously an in-line UV lamp will give you better performance but you'd need to do some significant modifications to achieve that. I prefer UV to ozone but either one can help breakdown bather waste into simpler organics that chlorine will less likely form persistent CC's with.....

BUT .....

You really need to let that tub breath more. I know exposing it to the air in it's location is going to cause you to take a big energy hit with the heater and evaporative water loss but that water needs to breathe. Monochloramine and dichloramine are both soluble in water and will reside there a long time; only nitrogen trichloride is volatile enough to outgas and that compound doesn't form very fast at normal FC levels (shock chlorination with low CYA drives NCl3 formation). The water needs contact with air and agitation to get those CC's to outgas. MPS and UV or ozone will help, but the primary problem I see is a very stagnant body of water.
 
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jseyfert3

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Why don't you try to see if you can install some cheap UV lamps on the inside of your cover? Might be a cheap and easy experiment to do rather than modifying your plumbing. Obviously an in-line UV lamp will give you better performance but you'd need to do some significant modifications to achieve that. I prefer UV to ozone but either one can help breakdown bather waste into simpler organics that chlorine will less likely form persistent CC's with.....
I did think of experimenting with a cheap UV light, I was thinking one of the many cheap submersible UV lights on Amazon, hanging the cord from the cover so it sits in the center of the tub when the lid is closed. But they are so cheap most reviews mention a life of a couple months if that, and I wasn't sure the cord is long enough.

But I didn't think of a light above the water. Something like a reflector with an aquarium light style (rubber boot) bulb connector, and a quartz UV light tube perhaps?

You really need to let that tub breath more. I know exposing it to the air in it's location is going to cause you to take a big energy hit with the heater and evaporative water loss but that water needs to breathe. Monochloramine and dichloramine are both soluble in water and will reside there a long time; only nitrogen trichloride is volatile enough to outgas and that compound doesn't form very fast at normal FC levels (shock chlorination with low CYA drives NCl3 formation). The water needs contact with air and agitation to get those CC's to outgas. MPS and UV or ozone will help, but the primary problem I see is a very stagnant body of water.
I can certainly run some pump cycles with the air valves open and see how much that helps. Do the CCs usually offgas fairly quickly?

On a related note would UV help break down and offgas CC's with less aeration, or will aeration still be needed to drive off the CC's even with UV?
 

JoyfulNoise

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I did think of experimenting with a cheap UV light, I was thinking one of the many cheap submersible UV lights on Amazon, hanging the cord from the cover so it sits in the center of the tub when the lid is closed. But they are so cheap most reviews mention a life of a couple months if that, and I wasn't sure the cord is long enough.

But I didn't think of a light above the water. Something like a reflector with an aquarium light style (rubber boot) bulb connector, and a quartz UV light tube perhaps?


I can certainly run some pump cycles with the air valves open and see how much that helps. Do the CCs usually offgas fairly quickly?

On a related note would UV help break down and offgas CC's with less aeration, or will aeration still be needed to drive off the CC's even with UV?
The thing to remember about CCs and hot tubs is that the CCs are ALWAYS going to form and be an issue if you use chlorine to sanitize. Supplimental oxidation (ozone, UV, MPS) will actually INCREASE CCs and THMs in the short term but lead to less persistent CCs over the long term. Once persistent CCs form (chloroform, chloroacetic acids, etc), they are very hard to breakdown by any oxidation method.

One reason why bromine users don’t worry about these issues as much is because you can’t tell the difference between active bromine and combined bromine in the sanitizer test. All bromine tests are total bromine. Also, bromamines are moderately good sanitizers in their own right so they contribute to keeping the water clean. Combined bromine compounds don’t outgas as easily so people are less likely to smell them but some people do have strong reactions to bromine compounds and can develop sensitivities.

If you intend to keep using chlorine then you could try modifying your tub with UV but you’ll need a fairly expensive lamp that has output at the UVC wavelengths. UVA/B isn’t sufficient. Just realize that the UV can initially cause the CCs to register a lot higher initially after use. You will need to open the tub up though. Try to open it up at least an hour per day or every other day. It shouldn’t sit for days with the cover on as that is going to keep the CCs in the water.
 

jseyfert3

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In the past we haven't had as much of an issue with CCs. They came after use but would at least mostly go away even with the cover closed. Not sure why now was more of an issue. Perhaps when back when I forgot to check it for a couple days after a heavy use and the water went cloudy. I did a SLAM to clear the water but perhaps it formed a lot of persistent CC's during that that don't normally form?

Even if that is the case, I learned it's not worth it to SLAM a hot tub to clear up cloudy water. If I ever do that again (hopefully not!) I would just dump and refill, even with a starting TA of 250-325 that I have to knock down on a new fill it's easier to just refill.

I used the tub this weekend and my wife remarked that the bathroom where my swimsuit was hanging up "smelled like a pool locker room." I dumped the tub and refilled last night cause we have friends coming tonight and that is NOT something I'm proud of.

You will need to open the tub up though. Try to open it up at least an hour per day or every other day. It shouldn’t sit for days with the cover on as that is going to keep the CCs in the water.
I will try to give it more air. One thing I can do is if I leave my air valves open when I check/add chlorine I can kick both the pumps on high before I shut the cover. This will draw fresh air in through the jets, but the pumps would turn off after 15 minutes so I can do it whenever like before bed and not need to go back and close the cover later. It would also draw air in during the twice a day filter cycles when it runs both pumps on high.

Downside is increased pH rise during standby of course.
 

JoyfulNoise

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If your water has a TA that high, then maybe you might consider setting up some rain harvesting barrels to capture rain water (near zero alkalinity and CH). There are many different varieties of rain tanks from commercial grade solid plastic to foldable ones. Modifying a gutter downspout is also pretty trivial. Even if you only captured 1/3 of the water your hot tub needed, it probably would help offset all the acid you need to control TA. Topping off with rainwater would also help keep the TA and pH in check (plus the garden and flower bed would prefer it to the alkaline water coming out if your spigots).
 

jseyfert3

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Supplimental oxidation (ozone, UV, MPS) will actually INCREASE CCs and THMs in the short term but lead to less persistent CCs over the long term.
Ah, this was something I had asked in my initial post. So MPS will help lead to less persistent CCs? Cause I have some on hand from the prior owners, I just haven't use it. If so, what's the best way to use it? Immediately after use so it can oxidize waste? And if so, I presume keeping only a minimum of FC for a night or so after use so the MPS can break down waste before FC gets to it?

My usual course of action after an evening of heavy use is to bring the FC to SLAM levels, cause if I don't there probably won't be FC in the morning.
 

jseyfert3

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If your water has a TA that high, then maybe you might consider setting up some rain harvesting barrels to capture rain water (near zero alkalinity and CH). There are many different varieties of rain tanks from commercial grade solid plastic to foldable ones. Modifying a gutter downspout is also pretty trivial. Even if you only captured 1/3 of the water your hot tub needed, it probably would help offset all the acid you need to control TA. Topping off with rainwater would also help keep the TA and pH in check (plus the garden and flower bed would prefer it to the alkaline water coming out if your spigots).
It is that high. My refill yesterday was 250 ppm. That's the lowest I've seen yet here. Usually it's 300-325. Relative to a pool it's very little acid used, but not having to do a lot of acid/aeration cycles on a new fill would be very nice, so that sounds like a good idea.
 

JoyfulNoise

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Ah, this was something I had asked in my initial post. So MPS will help lead to less persistent CCs? Cause I have some on hand from the prior owners, I just haven't use it. If so, what's the best way to use it? Immediately after use so it can oxidize waste? And if so, I presume keeping only a minimum of FC for a night or so after use so the MPS can break down waste before FC gets to it?

My usual course of action after an evening of heavy use is to bring the FC to SLAM levels, cause if I don't there probably won't be FC in the morning.
I would suggest the low end of 1oz by weight per 250 gallons of water. You would want to add it after soaking but before you add any chlorine. If you want to accurately track it, then you’re going to need the additional Taylor reagents to remove the MPS interference as that much non-chlorine shock will show up as a lot of CCs. MPS is also acidic so keep an eye on your pH as well.

Do note though - MPS will add sulfates to your tub water. That will reduce the life of your heater and can lead to damage to your Saltron SWG. So use at your own risk.
 

jseyfert3

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WARNING: UV-C is very dangerous to your eyes and skin and damaging to plastics as well. The following is done as a test, and NOT a long term solution regardless of how the test works. It also deals with cheap electronics submerged in water, which has additional risks.

I got one of the cheap submersible UV-C lights I mentioned off Amazon. These are intended for retrofitting inside an aquarium filter. Should do the trick of testing. I taped the cord to the lid to hold it in the center to avoid UV damage as much as possible to the plastics of the hot tub. The cover will get the worst hit but I'm not worried about that in a test as the cover is about toast and a replacement is currently being built. I would not do this with my new cover. The tube ended up floating, I should probably string a small stainless weight to the end so it's vertical which would get the most UV in the water and less on the cover and plastics.


So far I haven't noticed much difference, but it hasn't been in long. I put it in Saturday, and we used the tub on Saturday too so there was a whole new load of waste for the chlorine to break down. We probably won't use the tub much this week, and it's the period of days between use that I'm most curious about the results.
 

JoyfulNoise

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Most of the UV-C is going to get absorbed or scattered within the first few inches of the sleeve so it needs to be in a place exegete it will see water flow. If it could hang out near the filter intake, that would probably help a bit. Those are very low output bulbs, so they’re not going to do a lot in the short term.

Always wear safety glasses if you’re dealing with UV. Simple polycarbonate safety lenses will completely absorb in the entire UV spectrum. UV-C is known as “the cancer wavelength” because the UV photons at the wavelength can penetrate the epidermis deeply and cause DNA damage. Wear sunblock.
 
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jseyfert3

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I keep both the diverter valves in the middle positions when not using the tub. This means the low speed pump used for running heater, checking water temp (and pre-programmed ozone cycle) will push water up through the foot massage jet in the middle of the tub below the UV light when it’s running.

I’m pretty sure my glasses are poly but when taking the picture I made sure my eyes were behind my phone so I wasn’t looking at the light, and after that what I‘ve done is shut the light off before I open the cover, and turn it back on after I close the cover again.