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Old 01-31-2011, 08:52 PM   #1
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Water Heater Vent problems

I live in a house that was built 5 years ago. One year ago this winter we began to notice strong exhaust fumes in our utility room and the CO monitor in the basement frequently began alarming. We called the sub contractor who had installed the water heater flues. For $100 he did the following:
1- Said "yup, that's not venting right" after placing his hand up next to the vent hood.
2- Told me that I wasn't changing the heater filter frequently. However, I showed him my log of filter changes done every other month religiously since we moved in.
3- He checked the flue and told me nothing was wrong with it.
4- Vacuumed something out in the water heater, but said he was only able to clean a small area that sometimes needs to be cleaned.
5- Extended the 4" fresh air duct by about 4 feet so it is closer to the floor in the room.
I have not had any problems again until this winter (we live in a cold climate) when the vent began exhausting into our basement again and alarms are keeping me up at night. The top of the water heater even has scorched marks and melted plastic where the exhaust is burning the top around the hood.

I have considered a few options:
1- Call a different professional. Would I contact an HVAC pro or plumber? My concern is getting popped for another $100 for little help again.
2- Buy a new water heater (and bigger one as we are a large family that often "over-runs" the current HWH) assuming this is the problem. I am worried, however, that I will still end up with the same problem.
3- Installing a direct venting/power vent HWH. One of those high efficiency condensing HWH. My only problem here is running PVC piping outside. Can I insert the PVC piping inside of the 4" metal flue and run it down to my basement to exhaust a new condensing HWH that way"

Any suggestions or answers to my above questions would be very helpful and appreciated.


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Old 01-31-2011, 09:27 PM   #2
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You have a negative pressure in the house and it is causing air to come down the chimney and spill fumes into your house. Very few techs understand venting and neg pressures etc so it is hard to find one who does or suggest one. All you can do is keep trying. Where do you live and what style of house do you have. Ie: 2 story or rancher/bungalow etc. If your electricity costs are not too high I would suggest a 50 or 60 gallon electric heater instead. High efficiency direct vent units are VERY expensive, over $3000-4000 for a good one and are expensive to repair and not easy to get parts for. Most are foreign imports and expensive. You would have to shop around locally and see who sells them and get some proper info. The venting on them is large, 3" and not able to be stuck inside a 4" pipe easily or possibly not at all due to required couplings, etc and the fact it cannot be bent. Has to be run continuosly upwards and not down to a basement. Most of them are mounted on an outside wall and directly vented outside that wall.


"Cut it twice and it is still too short".

Last edited by yuri; 01-31-2011 at 09:30 PM.
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Old 01-31-2011, 09:47 PM   #3
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If I read correctly, your HW tank is on the main floor and not in the basement?

Where is the furnace, right next to it?
When its all said and done there is usually more said than done
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Old 01-31-2011, 09:58 PM   #4
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This really sounds like you have both your furnace and HW tank in the same room, closed door, not enough combustion air piped into where your furnace and HW tank are.

Have a look at the roof line where the flue pipe exhausts to atmosphere, is it the tallest point on your roof?

If not it may be back drafting if there is a higher roof right next to it.

Another test, turn your furnace off (temporary) turn on a hot water faucet to start the tank, is it back drafting?

If not it would indicate insufficiant combustion air.

To prove this, turn the furnace on, is there cold air coming down the draft divertor on the top of the HW tank?

It may not just be lack of combustion air, you may have a large leak in your return air duct, that is causing the room to go negative.

When its all said and done there is usually more said than done

Last edited by Jackofall1; 02-01-2011 at 06:27 AM.
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Old 02-01-2011, 04:02 AM   #5
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How high is your chimney above your roof? Is there a lot of snow around it, and could it be covering the flue cap? Is your furnace a direct vent? Is it piped up as 2 pipe or single pipe?
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Old 02-01-2011, 08:03 AM   #6
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A 5 year old home is probably very tight. Do you have a system used to turn over fresh air? Could it be pulling 'too much' combustion air from basement?

If so, temporarily turn off fresh air handler and see if CO2 problem stops. Then basement needs to be isolated from that handler and still get fresh air for utilities in basement from outside source.


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ducts , vent pipes , water heater

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