Confused on Chlorine Levels

[icecactus]

I purchased a used spa and I am currently trying to get the water balanced and the correct amount of sanitizer. So I have been doing a on of research on the internet (thanks chemgeek, waterwizard, nitro etc), but I am confused about some of the Free Chlorine numbers.

So my first question is Dichlor says 4-5 ppm, yet they say reentry is prohibited unless its below 3ppm....why? I don't understand this...

Most test strips and manufactures recommend 3-5 ppm for a spa. But they don't say at what CYA levels. From my understanding with 0 CYA, wouldn't this be a very harsh amount of chlorine and be hard on the equipment, swim suits etc?

For instance I bought a Chlormaker DO, they state maintain 4-5ppm. They say nothing about CYA.

Should I add 30 ppm CYA like some advise and do I need to up the free chlorine levels higher then 4-5 ppm in order to compensate for the reduced chlorine effectiveness?

Thanks!

 

[jblizzle]

Welcome to TFP!!!

I would advise you to completely ignore what ever numbers are listed on the pool products and just read and follow the recommendations on this forum. You are absolutely correct that the required FC level is a function of CYA level. And that with 0 CYA, a 3-5ppm of FC is going to be VERY harsh.

Have you read the sticky at the top of this forum about how to use chlorine in the spa. I recommend you use the Dichlor then bleach method as described there.

Ask questions if you still have any.

 

[icecactus]

Yes I have read it. Very good information. I am basically using that method, but instead of using Bleach, I am using the Chlormaker DO SWG. So I used Dichlor to build up my CYA, then switching to the SWG.

 

[Jabooh1]

You could also just buy CYA and place it in a sock and in the skimmer. That's what I did. That way you don't get anything else in the tabs.

 

[Kiss4aFrog]

Welcome to the forum Icecactus

 

[jblizzle]

Ok, well it sounds like you are on the right track, so maybe I am unclear what you actual questions were in the first post.

 

[chem geek]

So I used Dichlor to build up my CYA, then switching to the SWG.

Yes that is a fine approach and as was mentioned you can also add pure CYA directly instead of using Dichlor but either way works. Just note that an SWG is unlikely to provide enough chlorine to handle bather load from a soak unless it's an oversized SWG and you are soaking every day or two. If you don't soak frequently, then you need to set your SWG output level to maintain a background level of chlorine and need to manually add bleach after each soak to oxidize the bather waste.

Note that most people prefer to start their soak with around 1-2 ppm FC so that they don't smell as may chloramines during the soak. It's up to you. The higher level is more likely to last through the soak and would be important for disinfection if you were soaking with strangers (or anyone who might be sick).