Testing for 0 clorine?

[txrick]

I have been 'lurking' on this board since we had our pool put in a few years ago. I have received a lot of good info, thanks to everyone here.
Now to my question. Do anyone know if the TF 100 test kit can show 'Zero' chlorine (or next to it..). I need to drain my pool, and the city allows drainage into the storm sewer if the chlorine level is at or below .01 ppm. I believe the test kit can test to .1 or .2 ppm. Does anyone know a way to increase the granularity of the measurement, or perhaps another method to determine zero chlorine?

Thanks in advance.

 

[mknauss]

Welcome to the forum!
I would suspect any chlorine test, even the cheap ones, can tell you if you have 0 chlorine. When you put the reagent drops in, if you get no color change, you have 0 chlorine.

If you go to that extreme, be prepared to SLAM Process the pool when you refill it as algae will have most likely taken over. Also be very careful draining a pool. The process has a lot of risks. Especially depending on your pool type.

I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[Donldson]

Welcome to TFP!

I think the easiest way to make sure you are compliant would be to use the 25 ml sample size on the FAS-DPD to get a 0.2 ppm FC precision. After you confirm your FC number you can add a chlorine neutralizer and overshoot a bit to compensate for any possible testing error. But overall I agree with Marty, if the test shows clear then the FC is essentially zero. I have serious doubts that the city is actually testing to the range they state, it sounds like one of those specifics to placate the person who would try to claim that zero chlorine is impossible. You know there is always that person around somewhere

 

[txrick]

Thank you for your prompt responses! I have read the SLAM process and am prepared... I think... I appreciate the guidance on checking down to .2 ppm. About what I was expecting.... with an old test kit, I tried 10% of the water with the same amount of reagent, seemed to be somewhat close....
BTW I have a 5000 gal IG gunnite/plaster pool with Pentair in floor cleaner and pump/filter system

 

[aussieta]

be aware even tap water has a small amount of chlorine
so 0.2 will not be noticed

 

[cfherrman]

When you add the fas-dpd powder and there's no hint if pink your good. You could be extra safe by doing a 50 sample and add 4 scoops of powder but I don't think you need to be that safe

 

[mknauss]

IF the authorities happen to test your effluent - I bet dollars to donuts they use a dipstick. The testing methods discussed above are WAY over the head of any government entity monitoring this.

 

[Richard320]

There's another alternative that I use from time to time when I need to replace some water: the sanitary sewer. I have a cleanout on the back wall so it's not to difficult to run a hose to it. I figure a few thousand gallons of water ought to flush away any buildup in the pipes.