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Phil
Phil, Mechanical Engineer.
Category: Plumbing
Satisfied Customers: 7834
Experience:  Retired mech. contractor, shop owner, 51 yrs experience.
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I have a Rinnai RL75I installed in 5/12 and seven weeks ago

Customer Question

I have a Rinnai RL75I installed in 5/12 and seven weeks ago I have intermittent hot water in all faucets. The plumber who installed the unit has been at my house 10 times and rinnai sent a second plumber to check and even with Rinnai tech support no one can figure what the problem is since no error codes appear. I am at wits end since I found an inch of scum in bottom of a maytag dishwasher from cold water and dishes done in cold water and showers starting with hot and them turning ice cold. HELP HELP please!!!
Submitted: 1 year ago.
Category: Plumbing
Expert:  Phil replied 1 year ago.

Hello,

It is a bit surprising that in all those visits no one has figured it out.

The odds are in the 90% range that hard water scale has built up in the heat exchanger and restricted the hot water flow, so at at the shower for instance, cold water pressure which is then higher than cold water pressure over comes the hot water flow, stops hot water flow and then the flow switch in the water heater shuts the burner off.

Expert:  Phil replied 1 year ago.

We can do a few tests.

Turn the shower on wide open and to hottest water, next turn on the kitchen sink hot tap in the same way, and then tell me if the water heater flame ever shuts off and you get cold water at the taps or not, we can go from there without time limit.