It may be "cheaper" and less of a hassle to buy your RO water at a vendor or store. Here is why. If you do not own the home you are living in, there maybe much larger issues that come into play if any RO system you install leaks. Leading causes of homes flooding are from washing machines and RO systems. I learned the hard way.
I bought a RO system from Costco 17-18 years ago. Changed filters regularly. About 15 years ago after moving out of the house it was in and returned 1 1/2 days later, I came home to 2-3 inches of water throughout the house. A lid to one of the filters had a manufacturing flaw in the top that sprang a leak. My insurance company made me whole and covered everything except the RO unit. They paid over $37,000 in repairs and actually made the home better than what was original. Now, in my current home, my RO units have leak sensors that shut off the water.
If you do not own the house, I suspect even if you receive written permission from the homeowner to install a RO system, and if there was ever a problem, the insurance company of the homeowner would pursue you (via subrogation) for the loss to the insured homeowner. I suspect they would claim you failed to install the unit properly, failed to maintain it, and/or failed to install a leak sensor. The insurance company would do this to recover the amount of the claim paid by them to the insured for the loss.
Lastly, if any water leaks cause mold, the insurance company does not cover mold abatement. The homeowner is on the hook for that.
Again, you may own the current house you live in. If so, then you should have no worries regarding an insurance company and subrogation. Just make sure to install a leak sensor.
Good luck!
