Exhaust smell with natural gas water heater

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Old 07-21-20, 08:28 AM
J
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Exhaust smell with natural gas water heater

Noticed an exhaust smell in the utility room the other day. Had noticed a slight smell before but yesterday it was prominent. Tracked it down to the exhaust vent on the water heater. You can smell it in the opening between the water heater and vent. If I up the temp on the water heater to get it to fire up the smell goes away when the water heater is running. So it only seems to smell when the pilot is on with out the water heater running.
I live in the North East and it was extremely hot and humid yesterday. Wondering if that may have had something to do with it.
Just moved into the house about 3 months ago. Water is about 11 years old, so it is old but not too old.
Any help on figuring out what the smell could be from and how to fix it would be appreciated.

Thanks
Joe DIY
 
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Old 07-22-20, 11:49 PM
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There could be a negative pressure condition causing back-drafting.

Is there a furnace or air handler in the utility room? Is there an exhaust fan or clothes dryer in the utility room?

 
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Old 07-23-20, 09:29 PM
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Welcome to the forums.

It could also be cause by an attic fan without enough make up air.
 
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Old 07-24-20, 07:47 AM
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You should install a CO2 alarm in that room. You can pick one up at your local big box store. If it picks up anything, you have a problem. If it's reads zero all the time, you should be okay.
 
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Old 07-25-20, 11:52 PM
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tom may mean a "CO" (carbon monoxide) alarm, a great suggestion!
 
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Old 08-04-20, 11:16 AM
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Thanks for all the comments
Went home and checked pilot light and vent. Pilot light looked good and vent was clear.
Started unit back up and no smell. Been running a while and still no smell. Maybe a faint smell once in a while but could be imagining it.
In the utility room there is a boiler for hot water heat, washer and dryer and also a carbon monoxide alarm.
My guess is it was one of two things.
Smell might have been caused by cleaning chemicals or something that was being used at the time. Had a similar problem once when I was applying polyurethane to hardwood floors and dryer was running, smelled up the house pretty good.
Maybe as someone stated the dryer was running while hot water heater was running for a while and dryer created back draft. Will check dryer vents.

Thanks again for comments
 
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Old 08-04-20, 01:05 PM
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You need to check the heater flue when the dryer is running. Heater does not have to be firing. Hold a lighted match or candle near the hood opening on the water heater. If he flame is drawn toward the hood opening there is no backdraft. If the flame is drawn away from the hood then the dryer (or exhaust fans elsewhere in the house) is pulling air down the flue (a backdraft). Opening a window or providing another source of outside air could be enough to prevent the backdraft.
 
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Old 08-10-20, 10:37 AM
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Great idea. Will give it a try
 
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