Sanitizer Questions. Advice needed please.

[Maveri9720]

Hi all. I have been glued to the pool section since we decided to get a pool and I have never maintained a pool before. There I discovered the BBB method and will be using it once the pool gets set-up. It seems very simple and cheap and I was contemplating using it on my hot tub. I have read through all of the threads pertaining to using the BBB method to spas in the spa section and I am alittle confused and need some help please.

First off, I have about a 350g acrylic hot tub with an ozonator. We bought it last Sept and I have been using Dichlor as a sanitizer and for shocking. I have been lax on testing and dosing, mainly due to simple ignorance and laziness. Since I will be dosing daily on my pool, I want to get into the habit of dosing daily on the hot tub also. I have the Taylor K2006 test kit.

It is only my wife and I that use the hot tub and we MIGHT use it once a week on average, for 15 mins. Since my wife and I use the hot tub so infrequently, it would make sense that we could go longer in between our water changes, as opposed to the recommended 3-4 month interval? Based on the formula I have seen given here, we would change our water about every 390 days. Sounds good to me, but for some reason, I don't think that will hold up. I have read and understand it is about what goes into the hot tub that determines that, so if I am using bleach, it only adds sodium, so that shouldn't be a concern.

As far as I understand it, once I do a refill, I should use the dichlor to raise CYA to 20ppm and then from there on, use bleach for daily doses and for shocking, correct? I understand that my ozonator is better suited for a bromine system, but it still helps eliminate pathogens in a chlorine system, correct?

Couple basic questions:

How much bleach do I dose after each use and when do I shock?

What are the ideal param's for using the BBB on a hot tub?

When do I add enzyme remover and how much? (never used it before)

As far as for adding bleach, I read that I should add it when the jets are off to reduce outgassing and splash. I do have a 24hr circ pump running, so I can just pour it anywhere in the hot tub? What about adding it to where the ozone comes in, b/c there is a current there shooting into the hot tub?

Also, relating to outgassing, should I close all of the venturi's on the jets when we exit the hot tub, b/c the hot tub will cycle to maintain temperature and if the venturi's are open, the pH will rise and I assume more outgassing will occur?

I tried to understand some of the more technical threads as best I could, but alot of it was over my head, so I thought I would post my questions, regarding my situation and equipment, so I could get the best answers possible.

Thanks for everyone's help, advice and more importantly, their patience here. It's great to be able to rely on one place for friendly, but yet knowledgable advice regarding pool and spa care.

Mitch

 

[chem geek]

Mitch,

4 ppm Free Chlorine (FC) in 350 gallons is about 2 teaspoons of Dichlor or about 3 fluid ounces of 6% bleach. You can use The Pool Calculator for calculating quantities.

Are you saying that currently you are only adding some Dichlor after you use the tub and then don't add any sanitizer during the week between uses? That is certainly risky. Now that you plan on dosing the pool and spa daily, you will be properly sanitizing both.

You are correct that for the spa you initially use Dichlor until you cumulatively get to around 20 ppm added FC which will be close to 20 ppm CYA (you don't have to be exact -- anything in the 20-30 ppm FC cumulative range will be fine). After that, you switch to using bleach.

As for how much you need to add each day when you are not using the tub, that's something you'll have to experiment with. You will likely need to add 4 ppm FC after your soak since that's about what will be needed for 2 people soaking for 15 minutes in 350 gallons (the rough rule is 7 ppm FC in 350 gallons for each person-hour of soaking). However, during the week when you are not soaking the chlorine demand may be less.

The biggest problem you are going to have is the aeration from the ozonator which will tend to drive up the pH in the spa fairly quickly. Closing off the venturis when the tub is not in use will help a lot, but the ozonator by itself might still be an issue. Again, this is something you'll just have to see and you can lower the TA level to around 60 ppm to help reduce the problem (I wouldn't go below 50 ppm TA). Using Clorox Regular instead of off-brand Ultra bleaches might help a little bit at slowing down the rate of pH rise since Clorox Regular has less "extra lye" in it (it has a pH of 11.4 compared to most off-brand Ultra bleaches that have a pH of 12.5).

Add the Dichlor or bleach slowly and yes you can add it over a return flow -- if you have more than one then use the one that isn't from the ozonator. A spa usually mixes the water pretty well so it's not as critical where you pour.

You'll probably target a pH of around 7.7, a TA of around 60, FC of 4 ppm, CYA of 20 ppm, CH around 120 ppm if you want to avoid foaming.

You shouldn't need to use an enzyme. The chlorine will keep your tub clean and the ozonator should help with that as well (assuming it's producing enough ozone -- some don't).

As for how long your water will last, this will depend mostly on how much chlorine you end up adding since as you point out the main issue is a buildup of salt. If you had to add 4 ppm FC every day, then that's almost 200 ppm per month increase in salt. You probably wouldn't want to go much more than a year like that since spa components may not be designed for higher salt levels. If your FC daily addition during the week is less, then this is less of an issue. There were reports on other forums of people using the Dichlor/bleach approach that had their water clarity be outstanding even after 6 months of daily use, but most people even using Dichlor/bleach do replace the water just because it's easy to do with a spa. If you have lotions or oils when you soak, you won't be able to go as long without a water change.

Richard

 

[Maveri9720]

Thanks for the in-depth answer Richard. Everything you said makes sense to me, so that's a good thing. I wouldn't plan on anything over 6 months for a water change anyway.

2 follow-up questions:

- When should I shock? Is that based on CC's? I thought I remembered reading that over 1ppm was time to shock. Is that right?

- When adding bleach, I know you say not to add it while the pumps are running, but after I add the bleach, do I need to turn the pumps on to mix it up some or do I just let the circ pump take care of that? And does this apply to dichlor, baking soda, MA, etc?

Thanks again for the invaluable info.

Mitch

 

[chem geek]

Mitch,

Just as with your pool, you may not need to shock at all in your spa, especially with the light bather load you will have. I wouldn't measure the CC right after a soak since it could be high, but it will drop as chlorine oxidizes the ammonia/urea from your sweat. If you measure >= 0.5 ppm CC the next day or anytime except in the hour or so after a soak, then you can shock either with a higher dose of chlorine (bleach) or with a non-chlorine shock (MPS). If you properly maintain your spa's chlorine level, I suspect you will hardly ever need to shock.

I've always said to add chlorine when the pump IS running -- what you don't want is the aeration jets to be on since you don't want the chlorine splashing back at you nor aerating away. The same is true for other chemical additions. You want the circulation pump to be running.

Richard

 

[Maveri9720]

Thank you very much. I chose my words poorly when asking about the pumps/jets. I said pumps, meaning the aeration jet pumps, as opposed to my circ pump. My circ pump runs 24/7, so I tend to refer to pumps as the jet pumps. Sorry for the slight confusion.

I appreciate your time and help, as always.

Mitch