Spa Chemistry

Have not check my spa last few weeks. Finally finished with patio cover. I have just the simple two part test kit. Tonight I tested the water. Using orthotolidine tested for Clorine/ Bromine, the color comes out a red orange. The Ph test with Phenol Red comes out a dirty yellow.

I do not know where I am. I assume the clorine/bromide is low. But I am not sure if the Ph is high or low.

Anyone have any Ideas?

Your test kit ought to include color bars or the equivalent to help you interpret the results. If you’re missing parts, I’d get a new kit.

I would also strongly recommend a kit that lets you test alkalinity; if alkalinity is too low, you’ll have a hell of a time keeping pH where you want it. Iif alkainity is too high, you’re more likely to get scaling.

Anyway, the Wikipedia page on Phenol Red says yellow is below 6.8 and red is above 8.2. You want something in the low 7’s ideally, so a dirty yellow probably means a little low, but probably not too much.

I’ve never used orthotolidine in testing. This page says it’s mostly been replaced by a better test using DPD (which is what I’ve used). Yellow indicates the presence of chlorine; it will turn brown as you reach high levels. If it is red or orange, it sounds like chlorine is probably high.

Not missing parts. colors are outside of range. Sounds like Ph is on the low side. Now I know where to start.