The first plumber said that the 11 year old tankless gas WH was not providing hot water consistently probably b/c of a problem in the electronics on the motherboard. The igniter, gas flow and water flow worked well, but he did not know how to work on the electronics and suggested a plumber who was to fix it. This plumber came and said that the exhaust vent on this 11 year old heater was not the right one and he said this would be the reason the WH stopped working and vent should be replaced or new heater with right vent installed. He turned the 11 year old WH off. He did not check the motherboard as the first plumber had suggested. Question: which is most likely - that the 11 year old WH stopped providing consistent hot water b/c of a failed component inside of the WH or that the supposedly improper vent suddenly caused it to stopped providing consistent hot water. Thanks for your responses.

you should take a picture of the vent and send it to the manufacturer.
if it is an improper vent then you may be getting carbon monoxide into your home.
get that sorted out quickly so you can address the lack of hot water problem.

The WH and vent were replaced. My question is not related to the potential safety issue b/c that plumber did not confirm that there was a CO problem. My question relates to the most likely reason for an 11 year old WH to stop working properly: internal malfunction due to age or the vent that was as old as the WH.

The malfunction and the vent are 2 separate issues. However, if the tech determines the vent to be a hazard, there's no reason to repair the unit until that is taken care of. I know.......it ran for 11 years. But put yourself in his shoes. Could you walk away and leave a hazardous condition in someone's home?

If the heating core was NOT cleaned in 11 years, that would be enough to cause the symptoms.

IMHO I would never install a Tankless WH in my home. They are overly complicated, too expensive and require more attention to maintenance than a Tank WH. Many may argue with me on this but I am not convinced of any good reason to install one. Tankless selling point is space saving...but not for me.

srloren, well my friend from CA. we stand shoulder to shoulder on this matter.
I just checked my incoming cold water temperature. 44deg F.
so if I had a tankless and wanted to raise the hot water temperature to 130DEG F we are talking an 86 deg rise.
check the chart to how many GPM I would get with that kind of rise.

We're standing shoulder to shoulder to shoulder. I would quote a price (a fair price, mind you) for a tankless installation, apply smelling salts to revive the client, then quote the price for a tank.

keep the smelling salts handy.
you'll need them after you explain they need yearly flushing of the coil with a solution, some brands need the burner cleaned with mineral oil yearly, they need to have the condensate pump checked yearly, and the vents (in and out) must be checked for birds nests etc.

This was the best tankless ever, imho.






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believe it or not, I grew up with a similar gas tankless that gravity fed into a copper tank.
my father would light the tankless with a match and after a short while would feel the uninsulated copper tank to see how much hot water it had in it.
if he thought it was enough hot water, he turned off the gas to the tankless and we made do with what there was.

At the risk of exposing my location.....or near my location.....

Steve g did you take that picture of the Ruud tankless heater at the Raypak/Rheem training center?

I saw it on reddit.

Hi Steve,

Sorry for the delay in responding.

That Ruud heater is located in the Raypak/Rheem Training Center in Oxnard, California.

I was there a couple weeks ago for a sales/training class.

In the past I was offered a new tankless heater for free, if I installed it at my house.....I said "No Thanks"