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We recently moved into a property with 2 water heaters installed in the basement. During the inspection, we were told that the water heaters were relatively new, but the exhausts were "odd". Yesterday, we had a strong gas smell in the basement and promptly called the gas company. The representative told us that the cause was a downward draft of the flue gas.

A plumber came by and told us that he hadn't seen such an exhaust, and at first recommended we change the entire water heater, and after a while (seeing the neighbor's setup) told us to change the exhausts.

I have attached 2 pictures of the exhaust installation.

My questions are: Based on the pictures, is this a normal setup?

There is silver HVAC foil taped around the vent. I removed it off one exhaust and experienced a draft of air coming down in the basement, near the water heater. Would it help to reseal the duct with foil tape, poking holes in it, so the exhaust can escape? This would be a temporary measure till I get some more opinions/estimates.

Both Exhausts Closeup showing the silver foil around the duct

isherwood
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rs79
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  • Where are you located? these are natural gas fueled appliances? What is the make and model of the heaters? Do those windows open? – Tester101 Feb 03 '15 at 17:50
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    The Windows are the first issues I see, you are not supposed to exhaust under a window like that. Where is the Incoming Air coming from? Is one the Intake and one the Exhaust? If so, that is the other issue. Your intake may be too close to the Exhaust. – scooter133 Feb 03 '15 at 19:29
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    Those vents are likely too close to the window. The smallest distance I could find was 12" below a window, but this should be specified in the manufacturers installation instructions. – Tester101 Feb 03 '15 at 19:31
  • Are those "caps" open at the bottom? – Tester101 Feb 03 '15 at 19:32
  • Thanks for the queries. @Tester101, Yes, these are natural gas water heaters. The windows do open, but we rarely do open them. The water heaters are Kenmore 40 gal. heaters. – rs79 Feb 03 '15 at 21:07
  • @scooter133, the incoming air is coming from the top of these ducts. There are 2 water heaters - I would imaging that they serve dual intake (for oxygen to the pilot) and outgoing (for flue exhaust). I think you may be on to something with the exhaust being too close to the intake. They are designed to be vents – rs79 Feb 03 '15 at 21:11
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    They make concentric Ducts that can be used for both. If they are High Efficiency units you can even use PVC. Looks something like this: http://www.hotwater.com/lit/misc/197313-001.pdf The Exhaust shoots out the top, then the intake is from under the collar. This Spec says you need 12" separation for 50,000BTU or higher. If you could do something like in Figure 5 you might be able to deal with the Window Opening too. It should be 12" from the opening. – scooter133 Feb 04 '15 at 01:07
  • @scooter133, thanks for the link. I will share with the plumber. Sounds like this is the exact installation that is in place. My hunch is that wind eddy may have contributed to the downward draft and hoping that it was a freak combination of conditions. – rs79 Feb 04 '15 at 21:14

2 Answers2

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This is not a good example as the venting pipes are right below some windows which can leak exhaust gasses back inside the residence. This would be illegal in the state of Michigan.

ThreePhaseEel
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David
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  • Do you have a citation for that? (I agree it'd be silly if this *wasn't* forbidden by Code, but the citation would make your answer quite a bit stronger) – ThreePhaseEel Jan 27 '17 at 00:15
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I suspect this is a very well sealed home and insufficient fresh air is entering to permit the unrestricted exit of flue gas ; so some flue gas is released in the house. If so, There must be some duct to permit outside air to enter the house. I added a duct ( about 8" X 16" ) that brought outside air to a gas furnace in a situation like that.

blacksmith37
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