Chlorine level vs bather load

[jvf]

Hello,

My brother in law wants to switch his spa’s sanitizer to chlorine from bromine. I read an older post which stated that the approximate bather load was 7ppm of chlorine/hour. If the level was kept at 3-5ppm this would seem to mean that you’d soon have no chlorine left in short order even if you were by yourself. With four people wanting to soak, this would mean 28ppm of chlorine which, if dumped into the spa in the beginning would fry everybody entering. Or, someone has to add some chlorine every 15-30 minutes and you know that ain’t gonna happen. So, how to maintain a reasonable level of chlorine during use?

Thanks,
jvf

 

[setsailsoon]

Sorry, this is way out of my wheelhouse... but I bet @ajw22 or @kimkats would know.

 

[Jimrahbe]

jvf,

I believe that the rule of thumb is to add 7 grams of chlorine per person/per hour, after you are done soaking.. This is to oxidize the body waste left after the filthy humans get out..

Jim R.

 

[jvf]

Thanks Jim,

I use 6% liquid bleach for their exercise pool so I’d look up powdered chlorine and make the conversion. I do lots of testing for everything I’m involved in and figured I’d monitor things while people were in the spa and see for myself. It seems unanimous that some shock should be added upon exit. I could probably teach the household to do that.

jvf

 

[jseyfert3]

It seems unanimous that some shock should be added upon exit. I could probably teach the household to do that.

This is 100% needed. What I try and do is add enough when we get out that on testing the next day, my FC is at or above the minimum level for my CYA. This is usually 4-8 oz of 6% bleach.

 

[jvf]

Whoops,
Just checked and I have 10%. But, the process will be similar. After I get things running I'll post results.

 

[jseyfert3]

To answer your original question though, yes, you can totally tank the FC to zero while soaking for a long time, especially with lots of people. If it's me and my wife, I'm not too concerned. I just make sure it's in the target range for our CYA, maybe upper target range if we are planning to soak for a long time.

If we're having guests over and it's going to be a long soak, I raise the FC up to the SLAM level before we get in, to try and maintain some FC during the soak.

I have added FC during a soak (dribbled bleach into the skimmer with both jet pumps on), but only like once or twice, cause like you said, it just ain't happening most of the time. We're almost certainly running out of FC during multi-person, lengthy soaks...

 

[jvf]

Very interesting. We were using bromine but I never measured levels either during or after use. He itches occasionally after soaking and thinks it’s the bromine although literature states that bromine is less likely than chlorine to cause skin irritation. My wife thinks he just has dry skin because he works in the sun most days. Plus, it doesn’t happen every time. Water is balanced with proper Ph, etc. Could be the soap he’s using. There’re lots of things that it could be having nothing to do with the spa sanitizer but, it doesn’t hurt to try chlorine for a while.