FC not as Pool calculator predicts

[rodjm]

Hey everybody,thanks in advance!

I have 2 month old D1 Amore Bay with Ozone and UV and been following Nitro's and Chem Geeks recommendations. Just trying to nail down a system to work with the ozone & UV and have followed the recommendations in regards to Bleach, Borates and CYA

Here is where I stand:
Taylor k-2006
Flushed and drained when received 2 months ago
Just my wife and I every other day.
Water Temp 103f
FC via clorox ultra unscented
CYA 40 ( raised to with Dichlor )
CH 120
AL 50
PH 7.7
Borates 50 (based on the Pool Calculator measurements)
MSP weekly

When we get out I usually add the bleach. Based on Pool Calculator amounts the FC after adding 4 oz of bleach is lower, only 2ppm not 4ppm ( needs 8oz to register 4ppm). I have tried shocking with MSP 30 min prior to adding bleach with same results.

Any recommendations?

PS. Have a 2 month Taylor K-2006 and I was under the impression that R-0011L (Calcium Indicator) should be a deep blue. Mine is deep purple!! and has always been that way! Is it spoiled?

 

[chem geek]

When you add chlorine after a soak, some of it will be almost immediately consumed by the bather waste from your soak if your FC got to near zero during the soak. If you want to test the calculations, then you'll want to do so when adding chlorine when there is no bather load, such as testing in between soaks or just before your next soak. Since you soak every other day, I suggest you do a test during the day at least 24 hours after your soak and be sure to do the test when there is still some measurable FC, such as 1 ppm. Wait about 10 minutes or so with the circulation pump running before measuring again after adding the bleach -- do not wait more than 1 hour before measuring since the ozonator will react with the chlorine reducing its amount.

The Amore Bay says it's a 415 gallon tub so 2 people soaking for 30 minutes would need 5 fluid ounces of 6% bleach to oxidize bather waste which in 415 gallons would be 5.8 ppm FC. However, with your ozonator, you may not need to use as much bleach since it should be able to oxidize some of the bather waste. On the other hand, when you are not using the tub the ozonator will be reacting with chlorine so ozonators are of benefit when a tub is used a lot, but not when used infrequently. In your case, it's probably of some benefit.

As for the calcium hardness indicator dye, Taylor calls it a deep blue, but I agree with you that it looks more like a deep purple. The reagent is not compromised with that color. I don't what color it changes to if/when it goes bad.

 

[rodjm]

Okay I will try it before and when there is some FC showing. I thought I was accomplishing the same thing by shocking with MPS to oxidize bather waste.

When do you recommend using MPS and how much? I was under the impression it would be around 7 tsp for 415 Gallons.

 

[chem geek]

You don't need to use MPS at all. Chlorine will oxidize bather waste just fine as will the ozonator. MPS is just an expensive addition and is not necessary. It will also interfere with your testing by measuring as FC in the FAS-DPD test (it measures as CC in a DPD test) unless a Taylor K-2042 interference remover is used (the MPS will usually dissipate within a couple of days -- sooner if there is bather waste to oxidize). I know that Nitro's guide says to optionally use MPS, but since that was written there are many people using Dichlor-then-bleach without any MPS and have no problems at all. If you find that you get some persistent CC (measured before your soak, not after when it is expected), then you can see if MPS used periodically will get rid of it, but most people find they can control CC with chlorine alone, especially if you soak "clean" (i.e. without extra lotions on your skin).