Probably already been covered before but HDX (Home Depot) and Poolmaster’s Basic 5 Way test kit PH comparator / color blocks are way off (HDX and Poolmaster being the same test kit).
Discovered this when I got around to playing with my PH test meters. After calibrating both meters, I pegged my pool water’s PH at 7.5 (7.54 & .7.56 on the meters). Here’s a pic of the test water showing on the Taylor K-1000 color/comparator block - a remarkably close/accurate color match.
I then tested the same water using the HDX and the PoolMaster test kits, shown here:
Here is the results of that test:
As can be seen in the picture, these two comparator blocks have that 7.5 meter verified PH water up around the 7.8 color band.
I then added some “PH Down” to the water in very small increments and, after a couple of testing go rounds, got the test water to coincide with the HDX/Poolmaster comparator block’s 7.6 color (being more of an orange than red color). I re-calibrated my PH meters and tested that water. It came in at a surprisingly low value of 7.11 / 7.18.
For the better part of eight years, I used that HDX kit (heck, HD is my home-away-from-home on weekends - what don’t I buy there?). So for that time frame, I unknowingly was maintaining my PH numbers in a much lower PH level than what is optimal. I switched to TF-100 last summer following my replaster.
Less a reaffirmation of the wisdom of TF-100's choice of Taylor's PH test kits and more of a head’s up to those who may still be relying on the HDX/Poolmaster kit for their PH testing.