We have PoolMath (which is awesome!) so why not a dedicated page or a dedicated section in PoolMath for Spa Math? Many TFP users have either attached spa's or stand-alone hot tubs (sometimes both!!). Not that the math is vastly different, there's just some missing chemicals (like doing bromide/bromine calculations). Just a thought...i know this is mostly a pool forum.
As for PoolMath, is there any way to up-date the "Effects of Adding Chemicals" section to add in some calculations for chloride increase? I've already seen at least three threads in the last few months with people wondering why their salt tests are showing large increases and the answer is that some of their additions (muriatic acid mostly) increase chloride content. It would also be nice if the inputs could use units of gallons or quarts so that the user doesn't have to convert everything to ounces...not hard, I know, but just an "ease of use" thing.