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Rick
Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 19519
Experience:  Licensed Master plumber with 40+ yrs. experience.
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I have a rinnai #R94LSI water heater, worked perfectly for

Customer Question

I have a rinnai #R94LSI water heater, worked perfectly for over 7 years with no service at all.I live in nyc area with soft water. A couple of weeks ago I heard a very loud scary virbration or rumble type noise, did I mention LOUD & SCARY. Didnt last long, I have heard the noise a number of times after that. Read the installation manual,Code 12.Called service, Said I had low gas pressure. Called gas company. 7in. water column ?, lets say 7LBs. coming from street into gas meter, About 25ft. away is tankless water heater,6LBs. at inlet of heater, NOTHING ON. Opened 2 hot water faucets full,Dropped to 41/2LBs,no noise. Turned on gas dryer,gas boiler,gas oven,kitchen gas stove,washing machine hot water only,Dropped to 2LBs. gas pressure, NO noise,Why?.Noise is intermittent.Still scary
Submitted: 7 months ago.
Category: Plumbing
Expert:  Rick replied 7 months ago.
Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.Yes 7" water column is adequate gas supply pressure. Residential gas pressure is measured in inches of water column not PSI. 7" WC is about .25 psi. It sounds like your gas piping size is inadequate. If it was sized properly the pressure drop would be minimal when everything is running. The rumble could be delayed ignition. You need to have a plumber come out and check/service your water heater and have him double check the gas piping size while he's there.
Customer: replied 7 months ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Rick replied 7 months ago.
A phone call is an additional charge. If you still want to talk then let me know and I'll post an additional service offer. Or we can continue here if you like.
Customer: replied 7 months ago.
Rick. The gas pipe from the meter to the 25FT. run to the water heater is 1IN. black pipe. The water heater has been running for 7 years with no problem, Can you think of something else.Thanks
Expert:  Rick replied 7 months ago.
1" pipe is not adequate for everything you have connected to it. It's not even close to being adequate! You've been lucky that it's worked so far particularly in the dead of winter when you could be using most if not all those appliances at once. Your pressure testing indicates a real problem. Combine that with a a tankless that hasn't been service in 7 years and you have a recipe for problems. Even if the noise is coming from something else (no way for me to tell from here) you still need to address the issues I explained in my first answer. There's a very good chance that what you describe is from delayed ignition which can be caused by a dirty tankless burner and/or heat exchanger. Delayed ignition is a safety issue.
Expert:  Rick replied 7 months ago.
Also, a 12 error is a flame failure error which could be due to a dirty burner not just inadequate gas supply pressure.