When We First Turn On Hot Water We Hear This Loud Noise Outside

by Cindy Solomon
(Franklin, Tennessee, USA)

We have an external Hot Noritz tankless water heater that was installed in May of 2008. In March 2016 we had to replace the ignition switch. Everything was good until recently. For the last several months, whenever you turn on the hot water after it's not been used for a while I hear this loud "whoop" kind of noise outside.

The unit is on the bedroom side of the house and I can sometimes hear it in our kitchen which is on the other side of our house. We had a local plumbing company come out and service/clean it the other day. He heard the noise when he first got there (I turned on the hot water hoping it would make the noise and it did). He felt that after cleaning the unit that would make it stop.
It did not. It's still doing it. I am worried about safety issues (is it gonna blow up or anything?) but I'm also sure my neighbors--whose bedroom is just across the yard from our water heater--are sick of hearing that "whoop" noise every morning at 5:30 when my husband gets up to take a shower.

Does anyone have any suggestions on what the problem might be?

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Jun 09, 2020
Rating
starstarstarstarstar 		Big bang on ignition (backfire)
by: J

In back it did seem as if the gap was too big on flame rod... Closed the gap a little bit, it was not dirty just orangish in color out back together and so far so go...hope it helps
Jun 09, 2020
Rating
starstarstarstarstar 		Big bang on ignition (backfire)
by: J

Same loud ignition seems that has is mixing before ignition I have a rather large gap in flame for was going to try that.. My gas valve was just replaced a year or so ago.. Thinking that's not it...Will try gap let everybody know in a bit..
Mar 05, 2020
Rating
starstarstar 		Same issue
by: Anonymous

I have the tankless heater in my utility room. I have the same issue. The heater makes a loud bang when turning on. When outside you can hear this through the vent pipe as a "whoop" sound. I’m worried there is gas building up and causing an issue on ignition. I’m hoping to find some answers too.
Nov 11, 2018
Rating
starstarstarstarstar 		Loud Noise Source Located
by: Anonymous

I found the gas meter regulator to my home was defective. I had to buy a low-pressure instrument off eBay to diagnose the high pressure. Got the city to change out the gas regulator. Be sure the regulator has the proper spring range. I also spent major bucks on so-called technicians before I took it on my own to get the proper equipment to troubleshoot the unit.
Nov 09, 2018
Rating
starstarstarstarstar 		Power surge
by: Anonymous

Had a power surge at my house. Noritz tankless water heater now shuts off and gives no hot water...Noritz said to turn off and on to reset...Still doing the same thing and sometimes makes shaking growling noise..... Have had plumbers out 4 times still shuts down and smells gassy. Anyone any suggestions?
Mar 24, 2018
Rating
starstarstarstarstar 		Same noise from my noritz
by: Anonymous

I have spent $500 for certified serviceman and still have a problem. He checked fuel pressure and cleaned the unit. I have no idea what to do next.

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