Help? Why does CC go up after appropriate shock?

[duganderson]

I have a 400 g. hot tub. Currently, my Taylor 2006 says CA is 250, Ph is 7.4, alk is 90 and CYA is 22 (based on how much dicrlor I've added). I used the MPS interference chemical by Taylor to make sure my MPS is not impacting my CC and FC.

I've noticed that every time I shock with bleach (7.5 %) that my combined chlorine goes up. Yesterday my CC was 0.7 so I shocked with 10 OZ of bleach which should have raised FC by 14 or 15. I started with FC at 1.0. This morning my FC was 2.2 but my CC was 1.2

This seems to happen after every chlorine shock. Then, MPS seems to lower the CC over time. What are you ideas of what's going on here.

About two weeks ago, I did a double aww-some flush so I'm pretty certain I don't have a significant build up of biofilm. I use Nauture 2 with MPS and shock about weekly with bleach.

Thanks, Doug

 

[Jimrahbe]

Doug,

I can't directly answer your question as I don't know much about MPS... I have never used it..

That said, TC= FC + CC.. So it would be impossible for your FC to be 2.2 and your TC to be 1.2..

Thanks,

Jim R.

 

[duganderson]

Doug,

I can't directly answer your question as I don't know much about MPS... I have never used it..

That said, TC= FC + CC.. So it would be impossible for your FC to be 2.2 and your TC to be 1.2..

Ooooops.....I meant to say Combined chlorine NOT total. I edited that in my initial post.

 

[needsajet]

Usually, the CC comes from FC doing it's job on sweat and other body secretions.

 

[jseyfert3]

I've noticed that every time I shock with bleach (7.5 %) that my combined chlorine goes up. Yesterday my CC was 0.7 so I shocked with 10 OZ of bleach which should have raised FC by 14 or 15. I started with FC at 1.0. This morning my FC was 2.2 but my CC was 1.2

This seems to happen after every chlorine shock. Then, MPS seems to lower the CC over time. What are you ideas of what's going on here.

Have you checked your bleach freshness by adding bleach, mixing up with your pumps running for a few minutes then testing FC again to verify it has gone up to the FC level you expect it to go to?

Assuming your bleach is relatively fresh still, having a FC of ~15 in the evening an 1 in the morning means you have a high chlorine demand. This means either something is trying to grow, or there is a surplus of bather waste in your tub. When you add the FC it goes to work killing anything trying to grow and breaking down waste.

This seems to indicate to me that your tub is not getting adequate sanitation and/or oxidation during normal usage, and has built up a "backlog" that begins to be cleared when you add FC. My guess is the Nature 2 and MPS cannot keep up on their own. Try to maintain a continuous level of FC as we recommend here and see what happens.

The other thing to note is that I'm not certain but I do not think the MPS is lowering the CC over time. CCs naturally offgas from water.

Putting this all together, my hypotheses is this: You have a backlog of sanitation and/or oxidation built up when you add the FC. Anytime FC breaks down stuff CC's are produced, so you see an increase in CC's. You don't add enough FC for long enough to clear up whatever backlog you have, and you stop adding FC and rely on only the Nature2 and MPS over the course of a week. There's no FC so no CC's can be produced, and they slowly offgas. However the backlog remains so next week when you add FC it breaks down stuff and CC's are produced.