Possibly getting a hot tub

[Propbndr]

We may be getting a hot tub but I know nothing about them.

Are the same chemicals used as for a fresh water pool?
Is there a chart for the chemical levels?
Is there a benefit of using bromine vs chlorine?

 

[KrisIL]

I own a hot tub and it's easier for me to use Bromine. Less checking. Read the Chlorine and Bromine threads at the top of main page here: Spas and Hot Tubs and just pick one method you would like. If you choose Chlorine then you use exactly same chemicals as in your pool. If you choose bromine then obviously you will have to buy bromine for your hot tub.

 

[chem geek]

See the Pool School articles Using Chlorine in a Spa and Using Bromine in a Spa.

There are four main differences between spas and pools. First is that the bather-load is much, much higher in a residential spa compared to a residential pool. This means that the amount of oxidizer that needs to be added is mostly related to how many people are in the spa and for how long. Second is that spas are generally covered with no light and generally do not have algae as a concern. Third is that the water is usually at a hotter temperature which accelerates chlorine usage in between soaks but also allows for bacteria to grow very quickly (along with the high bather load that gives them plenty of nutrients) if the disinfectant level is not consistently maintained. Fourth is that due to the small water volume and higher bather-load, the water is periodically replaced in a spa (i.e. full drain/refill).

You do not normally use Trichlor pucks in a spa because with the hot temperatures they dissolve too quickly and with the small water volume it's too easy to overdose and have the pH crash if one is not careful. So for slow dosing, one normally uses bromine tabs instead. This works best if one isn't using the spa regularly (say, only on weekends) or if one has an ozonator that can make more bromine from a bromide bank. You can create more bromine from the bromide bank by using an oxidizer such as chlorine or non-chlorine shock (MPS). Usually one needs to periodically shock a bromine spa using chlorine to keep the water clear because bromine is a weaker oxidizer (especially if one does not have an ozonator).

If one uses the spa every day or two, then chlorine is added after every soak; if you do not soak regularly then you need to add chlorine in between soaks. The Dichlor-then-bleach method has one use Dichlor initially to build up the CYA level and then switch over to using bleach so that the CYA doesn't continue to build up. Alternatively, one could add pure CYA initially similar to what one does in a pool.

As for a chart with levels, for chlorine the CYA should be in the 30-40 ppm range and the FC should not get to zero in between soaks. Most people target 1-2 ppm FC for the start of their soak. The key is to add enough oxidizer after each soak such that there is still a chlorine residual at the start of the next soak.

Bromine is easier if you do not soak regularly because the slow dissolving tabs (or the ozonator with a bromide bank) maintain a bromine level in between soaks. It smells different than chlorine and some people don't like that. It's more expensive than chlorine (especially if one uses bleach).

 

[KrisIL]

See the Pool School articles Using Chlorine in a Spa and Using Bromine in a Spa.

There are four main differences between spas and pools. First is that the bather-load is much, much higher in a residential spa compared to a residential pool. This means that the amount of oxidizer that needs to be added is mostly related to how many people are in the spa and for how long. Second is that spas are generally covered with no light and generally do not have algae as a concern. Third is that the water is usually at a hotter temperature which accelerates chlorine usage in between soaks but also allows for bacteria to grow very quickly (along with the high bather load that gives them plenty of nutrients) if the disinfectant level is not consistently maintained. Fourth is that due to the small water volume and higher bather-load, the water is periodically replaced in a spa (i.e. full drain/refill).

You do not normally use Trichlor pucks in a spa because with the hot temperatures they dissolve too quickly and with the small water volume it's too easy to overdose and have the pH crash if one is not careful. So for slow dosing, one normally uses bromine tabs instead. This works best if one isn't using the spa regularly (say, only on weekends) or if one has an ozonator that can make more bromine from a bromide bank. You can create more bromine from the bromide bank by using an oxidizer such as chlorine or non-chlorine shock (MPS). Usually one needs to periodically shock a bromine spa using chlorine to keep the water clear because bromine is a weaker oxidizer (especially if one does not have an ozonator).

If one uses the spa every day or two, then chlorine is added after every soak; if you do not soak regularly then you need to add chlorine in between soaks. The Dichlor-then-bleach method has one use Dichlor initially to build up the CYA level and then switch over to using bleach so that the CYA doesn't continue to build up. Alternatively, one could add pure CYA initially similar to what one does in a pool.

As for a chart with levels, for chlorine the CYA should be in the 30-40 ppm range and the FC should not get to zero in between soaks. Most people target 1-2 ppm FC for the start of their soak. The key is to add enough oxidizer after each soak such that there is still a chlorine residual at the start of the next soak.

Bromine is easier if you do not soak regularly because the slow dissolving tabs (or the ozonator with a bromide bank) maintain a bromine level in between soaks. It smells different than chlorine and some people don't like that. It's more expensive than chlorine (especially if one uses bleach).

Well said.

 

[JVTrain]

I use the dichlor-then-bleach method in my tub. Works very well for me as I stay on top of the FC and pH... for the most part. I hate the smell of bromine tubs so I've stuck with chlorine. The only bad part for me is dealing with very fast pH rise when I refill the tub, because my municipal water has relatively high total alkalinity. After a few days of dropping the pH down every day, it stabilizes though. It's actually more work for me to maintain the hot tub than my pool, mostly because in the early summer, late fall, the kids are using the spa more than the pool to warm up so the bather load is high.

 

[pooldv]

We use bleach, borates and CYA in our hot tub also. Very happy with it. Been maintaining our tub this way for 18 months, use it at least 5 times per week. Good stuff.

 

[Propbndr]

Are the CH, TA, and Ph levels the same as a pool? I read somewhere that the CH has to be above 100 or foaming could occur.

Is decontamination the same as shock?

 

[chem geek]

As noted in the Pool School articles (same as the stickies at the top of this forum), the CH should be from 120-150 ppm to prevent foaming. Most spas are acrylic and not plaster so do not need calcium to protect their surfaces, but some is usually needed to prevent foaming.

As for the TA and pH, when using a hypochlorite source of chorine such as bleach you need the TA to be fairly low at around 50 ppm and need to use 50 ppm Borates (most easily added from boric acid). This is because spas have a lot more carbon dioxide from aeration due to spa jets, shallower depth, and hotter water. The pH target is usually around 7.7 or 7.8 but if 7.5 is stable that is certainly fine. If instead you are using net acidic sources of disinfectant/oxidizer such as Dichlor or MPS, then you may need a higher TA for the pH to not drop.

Decontamination is the same as elevating the chlorine level to a high level so is similar to shock (SLAM) except it's not done to get rid of algae. The use of Ahh-Some just before a water change and most especially for a spa that hasn't been purged of grease and biofilms before is recommended.

 

[pooldv]

Here is the article on using chlorine in your spa and the other levels.
How do I use Chlorine in my Spa (or pool)?

 

[Propbndr]

Thank you for your answers. I am trying to get educated before I get the tub and run into problems. Unlike a pool, on which maintenance is now second nature, a tub seems to be a new learning curve and more difficult.

 

[pooldv]

There is learning curve but not more difficult. Be not afraid grasshopper.

Once the initial levels are set I adjust ph about once a week by adding acid. And I add 1/8-1/4 cup of bleach pretty much every day. End of tub maintenance lesson.

 

[Propbndr]

There is learning curve but not more difficult. Be not afraid grasshopper.

Once the initial levels are set I adjust ph about once a week by adding acid. And I add 1/8-1/4 cup of bleach pretty much every day. End of tub maintenance lesson.

With my salt water pool, maintenance is: a daily check of skimmer baskets and pool bottom for critters, test fc & ph a couple times a week (rarely have to do anything but occasionally adjust the SWG output level). I am hoping tub maintenance will be similar.

 

[chem geek]

You'll need to add chlorine every day to your tub. Since you have a saltwater chlorine generator for your pool, you might consider getting the ControlOMatic TechniChlor for your tub. You would still add chlorine after your soak, but the SWG would take care of dosing in between soaks. You would still need to do the initial setup after a water change to get the TA low, probably increase CH to 120-150 ppm (to reduce foaming), and add some CYA and boric acid (unless you don't have much aeration or don't use spa jets).

 

[Propbndr]

I understand the CH and TA levels now. Thank you for the SWG link! That looks awesome. Is CYA necessary when using the bromine method? I thought is was only needed if I was going to use the chlorine method.

 

[chem geek]

CYA is only needed for the chlorine method because only chlorine binds to CYA to moderate its strength. For bromine, you get full-strength unless you use bromine tabs where there will be some buildup of DMH from the tabs, but we don't have details on the bromine/DMH relationship so don't know how much moderation there is in bromine strength. Bromine is a weaker oxidizer than chlorine when both are unbound (i.e. no CYA and no DMH).

Of course, if you go with the SWG then that is for chlorine and you should have CYA in the water for that.

 

[Propbndr]

The Techniclor manual talks about using Sodium Bromide Salt. Is this considered a bromine system?

 

[chem geek]

The TechniChlor Owner's Manual says it can generate chlorine or bromine. Which one it generates depends on whether you use sodium chloride salt or sodium bromide salt. I suggest you use sodium chloride salt and make chlorine. And yes, if you were to use sodium bromide, then this would be a bromine system.

 

[Isaac-1]

There is also the Saltron-Mini as another SWG retrofit option for hot tubs, I have been using one for about a year and half and overall it works well, my only complaint is the control works X hours out of 24 which I wish offered a little finer grain control as I find 2 hours per day a bit too little and 3 hours a bit too much, but I do have a small 3 person hot tub which only holds a little over 200 gallons of water, I suspect this would not be such a problem in a more typical 300-350 gallon tub.


Ike

 

[Propbndr]

When not in use, how often do you run the pump? It seems to be a huge waste of power to run it more that an hour a day, if that much.

 

[JVTrain]

Most tubs have a filter cycle run time that is variable. Mine has settings of 2, 4, 8, 12 and 24. This means every day at the same time it will run that long to circulate water. Your tub will also circulate any time it needs to raise the temp. My tub also has 3 "modes". Standard mode keeps the temp normally at the set point. Economy mode sets the temp to the minimum, 80 F, and only runs to keep it above that. Sleep mode runs enough to keep the tub above freezing nearly no heater run time. Brrrr.

That said, maintaining normal tub temps does burn the electricity bill here in the cooler months.

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