Taylor Phenol Red #4 pH Indicator Solution, .75 oz, R-0004-A

Taylor R-0004-A is phenol red #4 pH indicator solution in a .75 oz dropper bottle. It is the refill for the pH side of a Taylor test kit, sold on its own so you replace only the reagent you have used.

How it works

Phenol red is an indicator dye. Add the prescribed number of drops to a water sample and the sample takes on a color, which you compare against the pH scale on the comparator. The reagent reports pH, it does not adjust it, and the tested sample is poured away rather than returned to the pool.

Why the age of the bottle matters

Reagents do not last forever. Taylor recommends replacing them annually, because a bottle that has drifted still produces a confident looking color, just not the right one. Every acid and base decision you make rides on that reading, so a fresh bottle each season is cheap insurance.

Getting a clean result

Rinse the test cell with pool water before filling, hold the bottle vertical so the drops are consistent in size, and read the color promptly in good light against a white background.