There were initial problems where it turned the water red, brown, purple, but these went away after a couple of days. The company said that the color balance "can shift as the product settles in the toilet".
But the real issue is after things have "settled". The product does nothing. The reason is an interesting mixture of the product and the toilet design. The following is after using the product for about 2 weeks, and not seeming to get anything from it.
This toilet is an American-Standard Champion 4 model, designed to be low-flow and water saving and all that, so it doesn't have the standard "flapper" design to the water closet part of the toilet -- the tank above and behind the toilet seat. We put this one in in 2013.
If we look in the tank, we can see the tablet has crumbled, and is tinting the water blue. The longer it sits there, the blue-er the water. But it's always at the very bottom of the tank -- the blue tint is heavier than water.
The problem is that the flushing mechanism only drains the top 3/4 of the tank, meaning that the bottom part of the tank, where the blue tint is, is left undisturbed by flushing.
The result is that the toilet bowl itself then has none of the blue tint, but is almost completely clear water.
Now this may, or may not, be true of other blue-tinting toilet products, but certainly seems to be the case with 2000 Flushes.
