SLAMing Results

[Dellop]

I have been having trouble with the chlorine in my 215 gal hot tub. Lots of trouble getting FC above 0.5 on a consistent basis. So I decided to SLAM and here are my recent results:
Yesterday
Time - FC - CC
12p: 0.5 - 0.5 (added bleach to 20 FC)
2p: 1 - 2.5 (added bleach to 20 FC)
4p: 6 - 5 (added bleach to 20 FC)
6:30p: 5 - 5 (added bleach to 20 FC)
9p: 11 -3 (added bleach to 20 FC)
11p: 10 -3 (added bleach to 20 FC)
Today
8:30a: 1 - 4 (added bleach to 20 FC)
[edit]11a: 15.5 - 3.5 (added bleach to 20 FC)[/edit]

Just curious if this is a normal process or if something else is going on. There is a Nature2 filter in the tub, but I have never used MPS with it. We have only been using the tub for 3 weeks.
PH: 7.5
CYA: 50
TA: 60
CH: 280

 

[chem geek]

Welcome to TFP!

That is not normal in the sense that you've got a huge chlorine demand and you've got a lot of CC. Are you using a TFTestkits TF-100 or a Taylor K-2006 test kit?

You may have not been using enough chlorine to handle the bather load during the three weeks and it got to zero long enough for biofilms to form. There may also be leftover grease in the spa if it was new. I suggest you do a decontamination procedure and get either SeaKlear Spa System Flush or get Ahh-Some to add before you change the water.

 

[Dellop]

I am using the tf100 kit. I can't get any of the system flush for a few days. Is it worth while to continue the bleach regiment or just stop everything, wait, do the flush, drain, and start all over?

2p: 11.5 - 4.5
5p: 13.5 - 2.5

 

[chem geek]

You'll just be wasting bleach at this point but that's up to you. The bleach might be keeping a check on anything continuing to grow, but your chlorine demand is HUGE. Are you sure you don't have an ozonator that's on 24/7 due to a circulation pump that's on that long? Ozone breaks down chlorine, though usually not by that much (and it sounds like this problem only happened recently and not when you started out).

 

[Dellop]

No ozonator. It is a used tub, so maybe the previous owners left it bad?