Help buying a colorimeter to test pool water

Hi All,

I am in the market for a colorimeter to test pool water accurately & reliably. I have been searching equipment sites & am overwhelmed with the choices & price points. I don't want to break the bank, I don't think I need to, it's just colorimetry, right? So I'm hoping some educated opinions can keep me on the right track & away from a bad value decision.

I need to test:

- pH

- alkalinity

- calcium/hardness

- cyanuric acid

- free chlorine

Questions I need answered are:

- why do most colorimeters claim they test only for a subset of the above? Isn't it just a case of adding more concentration charts?

- anything wrong with buying a 2nd hand colorimeter?

- what are some of the more reputable lab equipment sites to look at?

- what would you buy considering the goals above?

Thanks in advance,

Brian.