Hot Water Heater, one way valve.?

Question

I purchased a marina about 4 years ago with a lot of cabins and stuff on them. I noticed upon working on some of the hot water heaters, someone has installed one way valves on the cold water side. In all my years of work I was told that this was dangerous, especially if you live in an area where the water has a lot of minerals in it, that the minerals could clog the vent blowoff valve and instead of the hot water pushing the cold water down the line it can blow the tank. Does anyone know about any laws or anything concerning this, I have installed a number of hot water tanks without the use of one way valves and had no problem with them.

Answer 1

are the water heaters in an elevated  area   say above the cabins in an attic space ? in that case you would be required to have a vacum breaker or check valves so the water heater won't siphon out  in the case  of a water supply failure .That would cause the elements to fail in a electric water heater and obvious  problems with a gas fired heater .if the  T&P valve  was to fail because of minerals i would think it would be an exteme case .

Answer 2

as long as your pressure releif valve on the water heater is okay the tank will not explode and like the previous guy said you do need one on there for an elevated hwh.  the t&p valve should be on the side or top of the hwh and blow off tube should be no less than six in off the floor and no more than a foot off the ground and it should never be capped or blocked.