Automatic Bleach Addition

[miatawnt2b]

Been reading this forum for a while now, and I must say I really appreciate all of the information found here. Thanks to finding this forum and everyones posts, I have a very stable/clean spa.

So I use the Dichlor/Bleach method due to personal health concerns with Bromine. My biggest problem is that it is very hard for me to maintain my Chlorine levels since our spa is so small. I really want a little bit more of a hands off approach. Is there any way to add the bleach portion automatically? I was hoping that there was a way of using tablets in a floater, but all of the tablets I can find are Trichlor which is a no-no from what I read.

Any ideas?

-J

[chem geek]

I assume you are not using your spa every day. Otherwise, it should not be a big deal to add chlorine after each use. You say you have a hard time keeping the chlorine. Is that because you are using the spa only once a week and only want to add it once a week? Is the chlorine dropping by 25% each day? If so, then starting at 8 ppm FC would get you to around 1 ppm FC after a week. Also remember that for every person-hour of soaking you need to add roughly 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize the bather waste. The FC level I mention to last for the week would be in addition to the chlorine used to handle bather waste. All of these numbers assume there is no ozonator.

You might consider Technichlor chlorine generator, though that's not cheap.

[miatawnt2b]

The problem is that we don't know when we will use it, so I've been adding bleach every night so the next evening its around 2-3ppm. This works out to about 1/4 cup of 6% per day in a 270 gal tub. After use I'll add about 5ppm per person plus the maintenance dose for the next day.

-j

[chem geek]

1/4 cup of 6% bleach in 270 gallons would be about 3.6 ppm FC. So if it ends up at 2-3 ppm the next evening, then you are losing half or more of the chlorine every 24 hours which is more than usual, at least for a fresh fill of water. You should be losing more like 25% per day, unless you have an ozonator (do you have one?) or the water is near due to be changed. The 5 ppm FC per person would be somewhat less than 3 fluid ounces of bleach (somewhat more than 1/3rd cup) and would roughly handle one person-hour of soaking so are you soaking for that long?

If you've had this fill of water for a month or more, you might need to add more CYA since it will get oxidized by chlorine over time. While this is around 5 ppm FC per month in most tubs, in a smaller tub with the larger chlorine swings the loss might be a bit higher.

I'm also assuming your spa is not exposed to sunlight and has a cover.

[waterbear]

May I ask what your personal health concerns with Bromine are?

[miatawnt2b]

I've had mild skin reaction to bromine tubs in the past. It is definitely time to change the water in the tub, and that is actually this weekend's project. Our soaks are usually about 30 min, and I add 1/4 cup per person (so I guess more like 4ppm per person) . I checked the CYA level last week and it's still at 40-ish (I usually add 1tsp a week of Dichlor to keep it in range) One thing I am bad about with my maintenance is shocking. I have only shocked the tub twice in two months (which consists of dumping a cup of bleach to add 14ppm)

So that brings me back to the auto addition. I actually have a peristaltic pump from my reef aquarium days. I was thinking of setting that up to add bleach by calculating how many ml/hr I need for the maintenance dose.

-J

[waterbear]

I've had mild skin reaction to bromine tubs in the past.

Was the tub being oxidized with chlorine or MPS? MPS is a known to be a skin irritant for many people. Just a thought for you since 3 step bromine would solve your other problem without needed to invest in a lot of expensive dosing equipment.

[miatawnt2b]

I've had mild skin reaction to bromine tubs in the past.

Was the tub being oxidized with chlorine or MPS? MPS is a known to be a skin irritant for many people. Just a thought for you since 3 step bromine would solve your other problem without needed to invest in a lot of expensive dosing equipment.

It's possible. It was a few years ago, and I'm not sure of the owner(s) maintenance procedures to tell you the truth. It was two different tubs, so I guess it's possible. I guess I could try 3 step, but I'd hate to buy all of the chemicals only to have it cause a problem. Maybe I'll stop by the store and see if they have small quantities of what I need.

-J

[chem geek]

I have only shocked the tub twice in two months (which consists of dumping a cup of bleach to add 14ppm)

:

I was thinking of setting that up to add bleach by calculating how many ml/hr I need for the maintenance dose.

If you maintain your chlorine level and add enough after soaks to handle bather load, then you shouldn't need to shock the spa.

As for how much bleach you need to add, you can do a 24-hour chlorine loss test in between your soaks (closer to when you next soak if there's a longer gap) where you raise the Free Chlorine (FC) level to your maintenance target (at least 2 ppm, but probably less than 4 ppm) and measure how much is lost in 24 hours. If your water is reasonably fresh, you'll probably lose around 25% of the FC level. This assumes you do not have an ozonator. With an ozonator, the loss rate can be twice as much or more.

So let's say you lose 25%. At 2-4 ppm FC that would be 0.5 to 1.0 ppm FC per day. With 6% bleach and a 350 gallon tub, that would be about 10 to 20 ml per day or 0.45 to 0.90 ml per hour if dosing was every hour. Of course, this is just an estimate and you'll need to test and adjust once you get your equipment and set it up.

[miatawnt2b]

well, I drained the tub, rinsed, refilled and added started the bromine with a sodium bromide/bleach shock. Guy at the pool supply gave me a couple of bromine tabs to try... I had to invest 10 bucks in the experiment for a packet of sodium bromide and a floater. We'll see how it works out, though after reading the bromine for beginners thread, I am excited that the system once tuned is almost completely hands off. Me likey.

How much time should I expect after initial shock for the bromine to dissipate and add the floater?

Thanks!

-J

[waterbear]

Ususally a couple of hours. Be sure to leave the spa uncovered and have all the jets and bubblers running, it speeds things up.

[miatawnt2b]

Thanks everyone for the help so far. The bromine went down to around 6 within a few hours and I set the floater to the lowest setting and covered the spa for the night. I checked bromine this am and it was at 5. I left the spa uncoveredall day to let the sun heat the water (living in the desert has its advantages) and about 6 hours later the reading was 1. No use or circulation other than the standard filtration which is set to circulate for 15 min every 6 hours and 5 min every 2 hours.

Does an uncovered spa eat bromine that much faster?

[waterbear]

Does an uncovered spa eat bromine that much faster?

Bromine, unlike chlorine, cannot be stabilized against lost from UV light. However, lF you were properly following dichlor/bleach method you did not have enough CYA in the water to stabilize against lost from UV either so the best suggestion I can give you is to get a floating solar cover like the ones used on pool and cut it to fit the spa. Make sure it is NOT a clear one (I would go for a silver on one side and blue on the other) and float the cover on the spa when you want to heat it with the sun. This should decrease a lot of the santizer loss from UV light, whether bromine or chlorine.

Just add enough bleach to reactivate the bromide reserve in the water and bring the bromine level back up. Start with about a tablespoon per 100 gallons or slightly less and test the level.