Thread: Backdrafting WH?

This is the second time in a month that I have encountered this issue. Both times were in one year old homes.

When I put my hand near (a foot away) the tops of these water heaters I felt excessive heat emanating from the draft hoods. Upon closer inspection I noticed that the plastic grommets where the water supply pipes enter the tops of the heaters were melted. Also, the pipe insualtion was melted (yes, I called out the combustible clearance issue with the insulation as I do on nearly every water heater I see in new construction ).

Both times the b-vents appeared to installed correctly and with listed caps. I recommended that the issue be looked at by a plumber to determine cause and course of repair.

My immediate thought was back drafting? It is definitely a fire hazard.

Any thoughts?

Thanks,

Eric

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Hi Eric; Have you considered the height of the vent pipe in relationship to the roof pitch? Many of the houses in this area have very steep roof surfaces and the wind follows the surface. I've found some vents that were two feet above the roof surface but still backdraft because they are catching wind from above. Some have blown the pilot lights out. Post a photo of the roof with the vent visible if you have one.

The only other things that come to mind are restrictions in or incorrect pitch of the vent pipe.

Boy, there can be several reasons for spillage. Blockage in the vent. Open return air duct. House it too tight - house is depressurized. Overfiring burner. Poor combustion air provisions in the area of the appliance.

I would say that it's more of a "safety" issue than a "fire" hazard since you are dealing with combustion gases venting into the home.

And while plumbers should be able to figure this out, such conditions often puzzle them. Like many contractors, the blinders keep them from looking at the whole list of possibilities. But that's not your worry.

Thanks for the replies.

As far as I could tell the b-vents were all to code and both attic areas where the units were located were well ventilated. On one of the houses the wind was blowing pretty hard outside but not on the other ( at least not on the day I was there). I highly recommended professional evaluation as to cause so I guess I did what I could do.

Thanks,

Eric

Be careful who you recommend. Most plumbers don't have a clue about this stuff. You want someone knowledgeable in venting, pressure diagnostics and equipped. That means a combustion analyzer, draft gauge, and micromanometer for starters.

Too much to speculate on. Need to consider the installation itself, the Combustion Appliance Zone (CAZ), the interaction of the house with the appliance, geographic siting and weather to name a few. While you may suspect leaky return ducts or a clothes dryer causing depressurization of the CAZ, only testing will confirm it.

Be careful with the term "backdrafting"-that is a diagnosis. Have you witnessed this phenomenon? Was it sustained for more than 45 seconds? How did you confirm the backdraft?

While such markings are clues to a problem, they are not a diagnosis unto themselves. Instead of recommending a particular trade, just state the capabilities you feel he needs such as I mentioned above. If a plumber comes in, checks the draft with a mirror or blows out a match, then later it does backdraft and causes an injury, you may be party to a "negligent referral".

FYI, look to Dale Feb's FIRE Service in a few months for a certification program for such training.

HTH,
Bob

Bob, what type of professional do you recommend we refer when evidence of backdrafting or spillage is present?

Recommend a contractor trained in combustion safety and certified by one of several organizations. The Building Performance Institute and the National Comfort Institute come to mind. I personally feel that this is a serious problem and that all inspectors should refer similar circumstances to qualified, certified technicians in the field.

Combustion gases do not belong in the living environment under any circumstances. On their best day combustion gases are a problem, and on their worst day they they are deadly. Signs of spillage or backdrafting are a serious matter and should be reported accordingy.

Originally Posted by Ed Voytovich

Recommend a contractor trained in combustion safety and certified by one of several organizations. The Building Performance Institute and the National Comfort Institute come to mind. I personally feel that this is a serious problem and that all inspectors should refer similar circumstances to qualified, certified technicians in the field.

That is all and good, but I can hear the question now. Who? And how do I find a person like this?

I like to be able to offer my client the information that they need in order for the problem to be corrected properly. Even with all my experience in this profession, I would not have a clue on who to recommend.

Is their one source that list folks with qualifications like this?

Your problem is not so rare, in fact it is very common in the newer tighter homes.
You call it back drafting , we call it draft reversal ,
this is casued when a natural draft vent originates in a low pressure area of the home and terminates in to a higher pressure area.

as we tighten up the side wall construction of homes it prevents a adequate amount of air from entering the interior enviroment.
at the same time in the higher regions of the home there is an equal amount of air exiting the home which contributes to the negitive pressure of the enviroment.
this presure difference can also be affected by any exhaust fan that does not have a make up air supply. every house has a number of these, bathroom exhaust fans, clothes dryers, range hoods ext.
another source of out going air is any non air tight penitration in the higher level ceiling suche as recessed lighting an the bigest one is the attic access
the only solution is to provide for and equal and slightly larger amount of air supply to the area of the natural draft device.

Helpful: Combustion Appliance Backdrafting | Remodeling Your Home? | IAQ in Homes/Residences | Indoor Air Quality | Air | US EPA

Originally Posted by Scott Patterson

That is all and good, but I can hear the question now. Who? And how do I find a person like this?

I like to be able to offer my client the information that they need in order for the problem to be corrected properly. Even with all my experience in this profession, I would not have a clue on who to recommend.

Is their one source that list folks with qualifications like this?

Great question, Scott. Both BPI - Building Performance Institute Inc. and National Comfort Institute Inc. : Performance-Based Contracting offer links to search for trained local individuals. I'm sure there are other organizations as well. Combustion safety is one area where home inspectors might benefit from additional training. There is a lot of information on the web, and several organizations that conduct trainings. Watch for events in your part of the country put on by ACI. Advancing Home Performance. - Home. Head for Google and see what's out there.

A certain number die every year from CO poisoning. No inspector wants their customer to fall victim to that hazard.

Sorry to say I do not know who you can recomend. The consulting service you need would require some one to come in with a blower door and identifly all your leaks. them you need some one to come in and seal all the leaks and yet another to provide make up air for all the devices in the home that require air for either combustion and or venilation.
It is fore this reason that we sell less and less natural draft devices , instead of tring to solve the pressure balance problem a solutiuon is change oit the natural draft device with one that incorporates direct vent technology and does not require air for combustion from the interior of the structure, not the answer you want to hear, but more than likly the easliest solution

Originally Posted by wayne stritsman

Sorry to say I do not know who you can recomend. The consulting service you need would require some one to come in with a blower door and identifly all your leaks. them you need some one to come in and seal all the leaks and yet another to provide make up air for all the devices in the home that require air for either combustion and or venilation.
It is fore this reason that we sell less and less natural draft devices , instead of tring to solve the pressure balance problem a solutiuon is change oit the natural draft device with one that incorporates direct vent technology and does not require air for combustion from the interior of the structure, not the answer you want to hear, but more than likly the easliest solution

Why would you blower door the house when the water heater is in the attic? How about check to make sure the soffit vents are clear and open?