Quote Originally Posted by waste
Evan, thanks for the info! Would a couple of drops of thiosufate correct the Rainbow kit and vice versa, could the Rainbow kit be used to test REALLY LOW pH if a few drops of bleach were added? (every year we lose a few copper heat exchangers due to low pH/ alk and I'd like to know how bad the water is so I can properly adjust it - as for why this happens, the owners use only tri-chlor pucks and [the antithesis of CarlD's advice] 'spend 2 - 5 minutes a year to buy a new heat exchanger' - no joke, there are some we replace every year and tell them how to avoid it.)
a drop or 2 of chlorine neutralizer should work to remove some interferance...don't really know abut the other way round. You would really need a comparator for the chlorophenol red to get an accurate reading...some soil testing kits have indicators in lower pH ranges...might be an option to explore.
Some people just don't want to deal with their pools. If they won't take the time to take care of their water I say make all the money you can off of them with the new heat exchangers every year!