Waterdrop AP431 Water Filter Cartridge, Replacement for Aqua-Pure AP431 Hot Water Scale Inhibitor for AP430SS (Pack of 1)

Fit great

It was the exact replacement for my tankless water heater de-salinator. It works well, delivered fast& good price from Amazon.

Fits and seams to work just fine.

This filter does a good job reducing the hard water drops in my shower and kitchen and bath faucets. I also feel better using this, knowing my washer combo and dishwasher will also not be forming wayer deposits. I originally got this for my new hot water heater, to keep it from corroding like my last one did.

There's a whole lotta variables that determine whether these will work for your system requiring a whole lot more water quality chemistry than I ever learned in school (that was a joke), but when you get it right, the calcium carbonate (whitish grey chunky stuff) on your faucets go away like magic . . and these last us nearly a year before that gunk starts coming back . . puttem just within 4' from the input side of the water heater is best for the pipes in your system. Too much use of these can cause premature pipe failure, too little and they don't work, and the pipes clog up . . you oughta consult someone who actually knows what they are talking about before you use, em, or maybe even consult the I-Ching, not sure, but under the right circumstances, like I said, bye bye calcium carbonate . .