This is about an honest, complete review as I can do.
My intent in purchasing was mainly to have treated water to protect my soon to be installed upgrade tankless water heater. I specifically bought from Hardless after I called several other companies directly- all of which couldn't answer any technical questions and were more interested in getting me to sign up for a "subscription" for auto billing replacement cartridges. When I called Hardless a delightful woman answered who was knowledgeable about the product, knew all features off of the top of her head and also knew what fitting were included and thread sizes etc. She had excellent and honest insight into what the unit did and didn't do.
The filter works as advertised. I could quickly feel the difference in the water. I don't have anymore mineral buildup in faucet aerators nor on outside of shower diverter since installing about 3 weeks ago. And pots no longer turn white after boiling water. I would have given the unit 5 stars, but I did have a small issue with a leaking fitting.
My house is plumbed with 3/4" PEX pipe and I chose to install it myself so it would be in place before my gas and plumbing guy came to install my new water heater. It was quite easy to install- would have taken a little over an hour if one of the fittings didn't leak. The unit comes with 1 fitting that screws directly into the filter, and an reducer coupling to go from 1"NPT down to the more common 3/4" NPT thread. This is what leaked on mine- I expect the male threads were bad. The part which screws directly into the filter uses a silicone rubber gasket to seal and this was fine. I called Hardless and told them about my leaking issue and the same knowledgeable woman answered and shipped me out replacement fittings rather quickly. 2 days after I installed the unit the plumber came to install the water heater and he took a crack at it but it still leaked so something was clearly wrong with the threads. Replacements arrived about 2 days later and I was able to quickly install them and unit is leak free. I am completely satisfied with the unit and that one bad fitting is the only reason i gave it four instead of five stars.
Although they do say it must be installed by a Plumber, I am sure there are other people such as myself who will install themselves and Two things I think they should mention in their instructions is that do not use cheap, hardware store Chinese made teflon tape. 1" threads are too large for this - if the tape says "milspec" anywhere on the label avoid it like the plague! Cheap teflon tape costs .99 and proper quality US tape is maybe $5. I use Oatey brand (Rainbow). T. Tape is not all the same.
Secondly It should be mentioned that this unit is best installed with a water bypass or shunt. This allows one to still have water to the house while servicing unit. Any decent plumber would do this automatically. It only adds about $20 in cost- 2 Tee fittings, 2 elbows, 1 extra shut off valve and about a foot of pipe.
Again- I am fully satisfied with the quality of the filter, the level of treatment it provides and was impressed and delighted with the companies Customer Service.