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Q: I had my water heater replaced after only a year because it wouldn't stay lit. They told me it was a ventilation problem because the heater is in the same room as the furnace and gas dryer. Well it keeps going off on a sporadic cycle. Even if the furnace and the dryer are not on at all it still goes off. Sometimes it stays lit for a week or two before going out. Other times it's every few days.

A: Venting is one of the more complex water heater issues. Does the water heater share a vent with the furnace? And are there ventilation screen in the walls or door of the space where all these things are located? Did the folks who mentioned this problem suggest a solution?

Q1: Yes, the water heater shares a vent with the furnace. they said I needed to re-vent the water heater into the crawl space. Previously to this water heater I had one for 12 years and this never happened. I bought a new one and it worked great for 8 months and then this problem started. they replaced the ignition system and that didn't help.

Then they replaced the whole water heater and the problem started up again a few weeks later. I don't know if the brand has anything to do with it, but it is a A.O.Smith Promax model # GCV 40 100. Also, the water heater is in a utility room. The door is always left open into the family room

A1: Hello: In addition to getting a handle on the combustion exhaust, it's important to understand the supply air. It may be that simply turning on a strong fan, like a kitchen exhaust, could depressurize the house and draw air back down the vent.... even with the water heater running. The furnace fan may be causing an imbalance, depending on where the return air grille is located and how much make up air is drawn in.

A good start to understanding the possibility of pressure problems would be to find someone with a "blower door" in your area. Your local utility company should have leads. This person will have equipment to measure even slight pressure imbalances so that the cause/s of the trouble can be found. Another possibility is to get a direct vent heater which would bypass any air pressure problems.

Q2: The one thing I don't understand is why everything worked fine for 12 years. Could this new water heater need more air than the old model?

A2: The fact is, the new heaters use a different design from the old ones. The federal government instituted a standard two years ago requiring use of a design that prevents the burner from igniting, say, nearby spilled gasoline. It might well be that the new heaters are more sucsceptible to being snuffed out in a situation like this. -- Larry (6/04/05)


Q: I have a natural gas water heater and i went down yesterday in the basement to find something disturbing. Around the combustion chamber, it was blackened and covered with soot on the outside shell and it looks like the ring around the drain valve was partially melted. Furthermore, it looks like soot particles were ejected from the combustion chamber area about 2 feet. Have you ever heard of this happening before and if so, what happened? By the way, there was no soot by the draft vent, only around the combustion chamber area.

A: There is a problem with the venting. The flue cound be blocked in the heater itself or the vent above may have a fault. The house may be operating at slightly negative pressure (because of exhaust fans perhaps). Soot or even a collapsed flue, from water pressure might play into it. Your water heater might be connected to the same vent that a power vented furnace is hooked up to. This is a dangerous situation that needs looking at fast. It does involve specialized knowledge. Make sure you qualify who ever you have look at it to see that they know something about backdrafting and air flow in a home. They should test for carbon monoxide as well. A heating or possibly plumbing contractor would be a good first place to look. Let us know how it goes.

Q1: The Water Heater and the Furnace use the same flue. Would this be the cause and if so, do i need to split the vents and make them seperate? Thanks.

A1: It's fine for both appliances to use the same vent as long as things are sized correctly and they are both atmospheric draft. That means what doesn't work well is to have one be atmospheric and the other use a fan to push out the products of combustion. Atmospheric draft is a weak force compared to fan assisted draft and often will be reversed by the stronger fan, spilling fumes out inside the building. The vent is everything above the heater. The flue is inside the heater. The vent could be fine, but if the flue is messed up it can produce the very symptoms you have. I don't mean to be an alarmist, but carbon monoxide levels in your home could easily be at unsafe levels as we type. Do try to find a qualified person to come have a look soon.

Q2: Ii had someone come out and look at it yesterday. They said that it was a buildup of soot on the inside of the heater leading up to the vent. Can it be cleaned out or is it time to put a new heater in? Thanks.

A2: The soot can be cleaned out. Typically, a plumber will scrub the flue and clean the orifices of the burner assembly. Also clean the floor beneath and around the water heater. Often it is dust and debris that have been drawn into the burner that cause the problem in the first place. Although I did hear of one example of this problem caused by a toasted mouse on the burner pan! -- Larry (3/02/05)


Q: Hello y'all, I recently relocated my water heater and vented it out the side wall as I had seen done at another house I was at. The vent goes up for 2 ft. then goes horizontal (with some pitch) for 32in. then turns and goes another 18 inches ending flush with the outside wall. I used single wall 4in. duct.

My first startup went well and I checked for proper venting by useing a match under the rim of the flue collar and feeling the heat come out the vent outside, all was well. It's been 2-3 weeks now and with the house shut up and when the water heater comes on I noticed a slight smell coming upstairs from a false register vent that is right above the water heater. I placed our co2 detector(after testing it) directly on the open vent and it didn't go off.

I noticed reading a few other post that the B type double wall vent pipe is better for promoting proper venting. It has also been windier this week. Is it normal for a little back draft? Because the detector didn't go off, is it ok? Would double wall pipe possiably fix the draft? Do I need to make the end of the vent extend past the outside wall and go up? Or am I on the wrong track altogether? Thank you for your help.

A: Hello: Venting can be tricky, even for people who have been doing it for years. Best would be for you to have someone experienced look at the arrangement you have, but I can tell from the description that there are some changes which would help. First, The vent pipe size should be whatever matches the draft hood on the heater. This could be three or four inch. It cannot be single wall passing through a wall, as this creates a fire hazard.

If you're in an area that can get cold, the entire vent pipe should be double wall to promote better venting when it's cold outside. The vent pipe needs to extend up well above the roof. As you have it now, any wind will affect venting. Also, venting low allows fumes to get in any nearby windows. An old rule of thumb is to have at least twice as much vertical pipe as horizontal.

Back draft should happen for no more than one minute and in a well designed arrangement will stop in about five seconds or less. Power vent and direct vent heaters can vent directly out a side wall. That may be what you saw. Your heater sounds like a conventional one and needs to follow the rules to be safe. -- Larry (10/14/07)

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