pH testing with high Chlorine

[rhythm]

I apologize if this has been covered several times here already.....

Using my Taylor K-2006 kit, if I want to test for pH when I've got the chlorine level up high (20 ppm or more), can I add a drop or two of thiosulfate (R-0007 in the Taylor kit) to the water sample before adding the drops of R-0004, and expect the pH test to work?

Thanks,
Greg

 

[257WbyMag]

Good question! I would also be interested in knowing the answer to this one.

 

[JasonLion]

Yes, and no. Adding thiosulfate will neutralize some or all of the chlorine but the thiosulfate will also shift the PH a bit. The result is usually better than without the thiosulfate but it reduces the precision significantly.

 

[Guest]

In a word, no. Adding thiosulfate will causes the pH of the sample to rise so you will not get an accurate ph reading. Either way (with or without the thiosulfate) the pH is going to read higher than it really is. You CAN use a properly calibrated pH meter (the keywords here are properly calibrated) to get a more accurate pH reading but why worry about it.I know people get stresses out about having the chlorine be most effective when shocking by having the pH low but unless you start out with VERY high pH, in actual practice it's not going to be THAT much of a problem. Remember, It's a pool, not rocket science!

 

[rhythm]

Thanks for the replies. I really wasn't all that concerned or stressed out about it, just curious if I could measure pH with high chlorine and not be wasting my time. Now I know not to bother, which is good information. I did lower the pH to about 7.2 before starting anyway. Thanks again for the help.

Greg