Thread: Carbon monixide in hot water

I came across another A.O. Smith water heater (1995 unit) that had the exact same soot above the TPR valve as my previous post (1994 unit). Again, the system appeared to draft normal under various conditions. However when I was testing the sinks and bathtub hot water, my carbon monoxide detector went off right away.. At first I thought it was the furnace but everything there was fine.

I tested the hot water again and immediately, I had high levels of carbon monoxide. Something is not right here but I have never heard of such a thing. All I could think of was that due due the house being vacant, that hydrgen gas was produced and set off my alarm..

Any help would be appreciated..

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I did some very quick research and came up only with hydrogen as a possible source of false positive. I got this from Bacharach's website.

What kind of meter are you using?

Hi,

The fact that the house is vacant is the tip-off. Hydrogen-sulfide gas has built up in the space above the water in the water heater from bacteria that are reacting to the anode rod in the tank. It's actually just as poisonous as CO but it won't hurt you at concentrations that you'd get from the small airspace above the water in a water heater tank. Be thankful you weren't smoking though; more than one person has gotten a surprise when turning on hot water taps of vacant homes while smoking.

ONE TEAM - ONE FIGHT!!!

Mike

Do you normally test the air around the plumbing fixtures for CO?
Or did you leave the meter on, nearby perhaps?
Just curious...

The meter is a UEi brand.

I always leave the meter on in my belt for the duration of the inspection. If it registers anything it is unsual and cause for concern. The levels were very high and it happened very fast. The hot water ran for quite a while and it still kept comming.. I was going to reommend replacement of the tank but wasn't sure if it would be ok after they move in.

Wearing the CO detector on your belt or on the strap of your bag sounds like a good idea. I didn't know they were that sensitive. What brand/model do you use?

Originally Posted by Jon mackay

The meter is a UEi brand.

.....

Could have been hydrogen gas. Cheaper sensors will give false positives on a lot of compounds.

Try it with a CO Experts or NSI 3000 low level CO monitor or a professional combustion analyzer such as Testo or Bacharach.

I used to have a digital Nighthawk outside my bedroom. I could tell when my wife used hairspray because it would spike to about 350ppm.

Bob

OK,
So if this is in fact hydrogen gas, I am guessing that replacement of the water heater would be smart as a precaution. The heater is from 1995 so its not like it would be a waste. It was popping also.. The big question is do you think that the soot above the TPR valve is somehow connected??

I have attached pictures of the two units..

Originally Posted by Jon mackay

The big question is do you think that the soot above the TPR valve is somehow connected??

No.

The hydrogen gas is inside the sealed system and the soot is outside the sealed system.

OK, got curious enough about the soot to e-mail AO Smith. I'll post their response.

That would be great...

Thank you. I am very curios about this one..

Originally Posted by Jon mackay

OK,
So if this is in fact hydrogen gas, I am guessing that replacement of the water heater would be smart as a precaution. The heater is from 1995 so its not like it would be a waste. It was popping also.. The big question is do you think that the soot above the TPR valve is somehow connected??

I have attached pictures of the two units..

The soot is a venting or burner problem or past problem. The hydrogen sulfide gas is inside the tank. The anode rod is the culprit. Neither one has anything to do with the other.

With the age of that unit I would say that it has had a good life and it could die at anytime. The popping is caused by a thick layer of sediment on the bottom of the tank.

Michael,
I was just curious if you ever received a response from A.O. Smith...

Is it possible that it is actually heat above the TPR valve that is making the "soot" stick in that one spot, so it looks like an upward smoke plume has been coming out of the water heater. Since the Anode is probably completely corroded, the flow of water over the years has placed enough charge on the unit to make some black substance, be it smoke, dust, corrosion, etc. stick in that one spot. It probably has more to do with the alloy of the valve than anything else.
It has nothing to do with the inside of the tank having Hydrogen built up and setting off the detector. The black mark is not part of the equation.
However, since the Anode is most likely gone, the flow of water does cause enough electrolysis to manufacture hydrogen.
Replace the water heater and your alarm probably won't go off anymore.

Sounds interesting..

Anything is possible..

I hope I advised ok on this one. I told them that the water heater is older and may go at any time. Budget to replace the unit...