Taylorof London Replacement Reagent FAS-DPD Refill Kit (Large) - Over 100 Tests

This is the go-to method of checking chlorine levels in pool water for professionals and those "who know". Simple, accurate, fairly quick and cost effective. I've been using these items for years and fully trust them. Nothing else I've tried comes close regardless of cost. Keep the powder sealed and indoors and it can work properly for years. If the white powder turns grey it is compromised and should be replaced.

Pros:-will last 4+ months-continued Taylor quality-refills my pool testing kit instead of having to buy a new one-chlorine reagent is larger than what comes in the original pool kitCons:None! A clean pool is a happy pool! Taylor chemicals testing is good quality, easy to use and saves a lot of money on a pool service.

My old powder turned purple/black and became a rock after years of storage, so I replaced the chemicals. This powder is closer to a fine white sugar and very easy to scoop. Both containers are well designed - the powder container is crisp to use and the liquid container makes it easy to apply drops one by one. Otherwise it's the same old chemicals from Taylor. Haven't found anything better so far.

New, good expiration date, good price, timely delivery.

I've tried to be lazy and use the quick strips to test my pool chemistry, but I've never found any brand to be accurate for testing free chlorine. The FAS-DPD color titration test is just the only way to go. Chlorine is expensive and if you run out of it after super-shocking your pool trying to get the test strips to show that there's more than a tiny bit, you'll end up a green pool and then a clogged up filter, and maybe too much cyanuric acid depending on what shock you were using and your pool is just going to keep sucking cash. As soon as I went back to this test, I have been managing my chlorine usage better and the pool and filter are needing a lot less maintenance.