# noritz water heater problem



## bkplumber (Jan 24, 2011)

I installed a noritz tankless water heater in a new construction home. Since homeowner moved in I've been trying to figure out this problem. When they turn on cold water anywhere in house the heater makes a thunk thunk sound. I installed check valve on hot and cold water lines at heater. That didnt work. I've installed many of these same units and have never had an issue. Called 1800 number and cant get no help from them. I know that one of you awsome plumbers can help. The reason I installed check valves is because I thought that maybe when the cold water was turned on the heater was detecting a pressure drop and was trying to fire up. Thats what it sounds like. Fire up then shut down or thunk thunk! I just hate when I cant solve a problem.


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## smellslike$tome (Jun 16, 2008)

bkplumber said:


> I installed a noritz tankless water heater in a new construction home. Since homeowner moved in I've been trying to figure out this problem. When they turn on cold water anywhere in house the heater makes a thunk thunk sound. I installed check valve on hot and cold water lines at heater. That didnt work. I've installed many of these same units and have never had an issue. Called 1800 number and cant get no help from them. I know that one of you awsome plumbers can help. The reason I installed check valves is because I thought that maybe when the cold water was turned on the heater was detecting a pressure drop and was trying to fire up. Thats what it sounds like. Fire up then shut down or thunk thunk! I just hate when I cant solve a problem.


Which model? What is the house water pressure? Get rid of the check valves. Does "burner on" indicator light when you open any cold tap? If so you have a cross connection.


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## bkplumber (Jan 24, 2011)

Im going to have to find out model,I do know that our city water is regulated to 65 psi. The burner on lite only comes on when hot water is ran. No cross conections I have hot water where its needed. If it was crossed it wouldn't be hot. I even checked all of the pressure ballance tub and shower valves for problems


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## bkplumber (Jan 24, 2011)

Model was I wanna say N93 9.3 gpm. Will the check valves hurt anything?


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## Surfing Plumber (Sep 27, 2011)

what size is the gas line? sounds like gas manifold pressure is off therefore it makes a loud sound. The heater is compensating the insufficient gas supply to fire up the heater. 

Get a digital manometer and check the gas pressure!


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## TanklessJoe (Dec 7, 2011)

Is the interesting noise coming from inside the twh or from the venting area? any large vibrations? 

I'm guessing its a venting problem


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## TanklessJoe (Dec 7, 2011)

also please answer what model it is? is it sv or dv? condensing or non-condensing?


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## liquid plumber (Nov 25, 2011)

yeah im all for removing the check valves. do you have the valve kit for flushing the heat exchanger? if so, isolate the unit and let the water rip, see if you still get the noise. the system works on a flow switch not a pressure trigger, so is the flow switch malfunctioning? as someone suggested the gas may be undersized and when the secondary burner kicks in it may be starving for gas, the noritz modulates the gas consumption with multistage burners. does the noise only happen when you are drawing maximum water volume? or even when you draw 1.5 gpm?


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## plumbingintexas (May 27, 2010)

did u see there is a recall on this brand?


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## CTs2p2 (Dec 6, 2011)

It doesn't thump thump when hot faucet is opened, only opening a cold side faucet makes the heater make a noise? Is this noise on the cold line and only being heard through the heater and not actually from the heater? Water hammer or unsecured pipes maybe?


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## Surfing Plumber (Sep 27, 2011)

plumbingintexas said:


> did u see there is a recall on this brand?



uhh...did you see that it is *NAVIEN* that has the huge recall??? 

http://www.navienamerica.com/event/notice_view.aspx?idx=12&skin=notice&kind=view


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