I live in a 10-unit cooperative apt. bldg in NYC; we are self-managed, and every apartment has a director on the board.

There was a recent requirement by NYC to install backflow inhibitors on buildings our size. We were able to get a double check valve (DCV) instead of the more elaborate & expensive RPZ (reduced pressure zone) device.

One of the issues that has come up is whether you have coin-op washing machines, and how many, etc., etc., and one of the possible solutions is to install separate 3/4" RPZ (reduced pressure zone) devices on the washing machine's water line itself.

Does anyone know how much it would cost to install those, and how convoluted it is?

On Amazon.com, I saw 3/4" rpz's for $50, and $170, and $270. I don't know which are appropriate for a single washing machine, and I don't know how much it would cost to install.
Does anybody have any ballpark guesses?

And the building-rated RPZ would have involved building some sort of drain, since the RPZ sends the excess backflowing water out of the device and into a drain.
Do the little ones need that draining capacity? How hard is it to install? Of course there is a drain line nearby, since it would go on the water line close to the machine.