The Watts OneFlow uses TAC (Template-Assisted Crystallization), a technology that shows some promise. I do have some reservations about TAC for use in a residential application.

1) The media has to be replaced after two years. Replacement schedule is time-based and independent of the amount of water passed through the system.

2) The media requires that there be NO copper in the water.

3) They are costly - $450-$800 for a cartridge system. Plus the cartridge has to be replaced every two years at a cost of around $300.

4) While studies have shown TAC to prevent scale formation, they have not looked at redissolution of the crystals, which is a very real possibility in a residential system where most of the time water is sitting idle rather than flowing constantly.

5) Those studies I was able to find were sponsored by Watts so were not independent.

Does anyone else have feed back? I am also considering this system. My concern is also if the one flow system is adding anything that could be harmful back into the water.

I don't have any feedback, but am interested in this topic myself. I've been interested in the Watts One Flow for about 4 years now. I know the One Flow has passed a tough German purification certification.

But since this was developed as a commercial/industrial product they don't have much of the residential market covered. I'm interested, especially how it can reverse some of the buildup we've already got around the home.

My concern is if the formed crystals have any impact when consumed by people. Are they inert and pass on through humans without any impact?

I bought it and had it installed a year ago as part of my new tankless water system, to extend the life of it and my aging washer, dryer and dishwasher etc. I can't really say much about it other than I had a bad problem with water scale and it seems to have alleviated it, to what degree I'm not yet sure but my kitchen faucet used to plug up badly with minerals and it seems to be doing better now. I'm just getting ready to replace the outer carbon filter for the first time which will cost me about $130.

Why not just do a water softener?

Slippery, greasy feel with water softeners. Hard to adjust to feel 'normal'.