Free chlorine loss

[DanWC]

Just curious what could be depleting my free chlorine levels?

We got in the hot tub on Wednesday and FC was 4.5 after getting our. So I did not add anymore chlorine. Hot tub stayed covered until today when we got in and FC was 0. CC was also 0. So I’m left wondering how it got to 0.

Could it be the case that FC was still being used after we got out and I tested to clean contaminants we left from being in there Wednesday night?

 

[Mdragger88]

Yup & just like a pool, The tub will consume some fc all the time. Only worse because of the much higher bather load.
It is a closed system much like a large bathtub that gets used over & over without exchanging the water.
You need to dose with enough chlorine after using it to not only account for your current bather load, but also your standby fc loss until you will dose again or nasties will proliferate quickly in the warm water.

How do I use Chlorine in my Spa (or pool)?

If you have a question about any information within this Sticky, please start a new thread for yourself where you will receive very quick responses to your specific questions. Thank you! Introduction There are two main things to consider when maintaining your hot tub water, Water Balance and...

www.google.com

 

[wireform]

Be aware the new hot tubs would need to be purged prior to first use due to the fact water is left in the plumbing from testing and who knows if anything started to grow from the stagnant water. This is what you may have going on.

 

[Mdragger88]

Approximately 1ppm fc standby loss per day is not necessarily unreasonable.

 

[phonedave]

You don't mention the details of your tub in your signature, but if you have an ozone generator in your tub, that will eat FC at quite a significant rate as well.

My tub, with an intermittent ozone generator - I don't have a circulation pump that runs 24/7 so mine only make ozone during filter cycles, will drop +/- 2 ppm of FC a day just by sitting there.

 

[Mdragger88]

Update your signature to include your hot tub & its info (ozone, uv, swg etc)
There’s quite a few factors that can be at play when considering standby fc losses- no two tubs are the same.
You just have to test frequently to learn how your tub behaves & feed it when you know its going to be hungry.

 

[RDspaguy]

feed it when you know its going to be hungry.

Ok, that's just disturbing.

 

[Mdragger88]

Ok, that's just disturbing.

Pro tip* it’s always hungry

 

[Mdragger88]

Its a new twist on the old @Richard320 advice “ A pool/spa is like a pet, you gotta feed it every day whether you play with it or not”.