Question on moving vent pipe in utility room

[Raymond Fries]

Well I got my humidifier water line moved to make way for the cabinet I am building. To make everything fit, I need the top of the cabinet to be about four inches from the ceiling. I pushed the vent pipe up into the attic about 5 inches. In this picture, the bottom of the pipe was 7" from the ceiling.

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Our heating contractor told me once this pipe was just a safety measure to prevent gas buildup should there ever be a leak. Does anyone know if there is a building code rule that specifies how far this pipe must extend down? I thought about removing it and putting a piece of 1/4" hardware cloth in the opening but was not sure if that was a good idea or against building code.

Thoughts please...

...Thanks

[George Bokros]

Maybe in your community but I have never seen nor heard of something like that.

[James Pallas]

Well I got my humidifier water line moved to make way for the cabinet I am building. To make everything fit, I need the top of the cabinet to be about four inches from the ceiling. I pushed the vent pipe up into the attic about 5 inches. In this picture, the bottom of the pipe was 7" from the ceiling.

370503

Our heating contractor told me once this pipe was just a safety measure to prevent gas buildup should there ever be a leak. Does anyone know if there is a building code rule that specifies how far this pipe must extend down? I thought about removing it and putting a piece of 1/4" hardware cloth in the opening but was not sure if that was a good idea or against building code.

Thoughts please...

...Thanks
Raymond, I'm guessing some here but I would say you have gas appliances located in that room. If so that pipe is for replacement and combustion air for those appliances. If that is the case you should not block that pipe. That air is needed for proper operation of gas appliances.
Jim

[Raymond Fries]

There is a gas furnace and gas water heater in the room. I have no intention of blocking the pipe. There will be at least 2" between the pipe and the top of the cabinet. If I can raise the pipe this high, I can install a cabinet 3' high. Under the cabinet will be enough space to hang the mob, broom, etc..

I am comfortable with the clearance in the design. I just could not find a rule that required the 8" pipe to extend into the room by x# of inches.

[James Pallas]

There is a gas furnace and gas water heater in the room. I have no intention of blocking the pipe. There will be at least 2" between the pipe and the top of the cabinet. If I can raise the pipe this high, I can install a cabinet 3' high. Under the cabinet will be enough space to hang the mob, broom, etc..

I am comfortable with the clearance in the design. I just could not find a rule that required the 8" pipe to extend into the room by x# of inches.
Raymond, the requirements are in the mechanical codes. I can't remember the exact numbers. It is a square inch per thousand BTU requirement. Half of which to be supplied at burner height and half from draft diverter height. In any case it is important to have it for proper combustion.
Jim

[Lee Schierer]

Modern high efficiency furnaces with pvc inlet and exhaust piping do not need room vents. Some contractors will short change buyers by not installing the inlet air vent piping which is not proper installation. They do it to save costs.

[Rich Lester]

Jim is correct in pointing out that the pipe is probably make-up air for combustion. The mechanical code refers to it as combustion air and in that code section it refers you to the International Fuel Gas Code to determine combustion air requirements for gas-fired appliances. That code utilizes BTU requirements for the appliance as well as the area of space the appliances are in to determine the necessity for combustion air. Other things considered are if the appliance is naturally vented or power vented.
So with that being said, and with what Lee added as to the age and type of ventilation/air intake system, the best place to look for the requirements is in the installation manual that came with the appliance. The manufacturers usually break down the requirements for their particular product in them. Depending on the room size and where the furnace and water heater can draw air from you may just be fine with where you have positioned that pipe.

EDIT: If indeed that pipe is combustion air for the appliances and that air is pulled either from the attic or outside you will have a draft of cold air entering mainly when the appliances are running. It will also be a source of heat loss just going right out the pipe. Google combustion air damper for a way to eliminate those conditions. It is a damper applied to the pipe that will automatically open when the appliance thermostat calls for the burner to run.

[Doug Garson]

I would question the qualifications of the heating contractor who says it was to prevent buildup of gas in case of a leak. I agree it is a combustion air supply.

[James Pallas]

I really urge anyone dealing with this to take it very seriously. The outcome of a suppressed flame on a gas fired appliance is the production of carbon monoxide, a deadly gas. I had the occasion of investigating the deaths of a grandfather and his one year old grandson years ago now but worth mentioning here. Dad had changed the furnace filter and did not get the blower door fastened. Furnace and water heater in a utility closet. The open blower overwhelmed the combustion air vents and the monoxide was pulled into the circulating air. The whole family was sickened overnight but the two most compromised by age passed. Every year at this time, first cold weather, these things seem to happen. I know that utility room gets cold and such but know what you are doing before you mess with that venting, PLEASE.
Jim

[Larry Frank]

I think James makes a great point. I will add that the use of CO detectors is important. I recommend the ones with a digital read out.


A number of years ago, I noticed ours which normally read zero was occasionally showing 7 ppm. I called some furnace people and two said not to worry. I finally got someone to look at the furnace and the gas furnace had a crack. While I know that they alarm at a much higher level, I was glad to get an early warning when I had young kids at home.

[Raymond Fries]

Great tips guys. I do have carbon monoxide detectors installed. The furnace is a high efficiency model with the PVC venting. This was installed about seven years ago. The water heater is gas and the washer and dryer are electric.

I will seek professional advice before I complete the project. I just cannot imagine that pushing the pipe sleeve up in the hole seven inches will matter. As I stated earlier, I have no intention. of blocking or restricting air flow to this pipe. The top of the cabinet will be about 5" from the bottom of the pipe. In my mind, this is plenty of room for air flow.

I will post what my heating contractor says. Maybe that advice will help someone else.

Edit. To the point Rich made about combustion air, I do not think the room has ever had cold air pulled into it. At least I have never noticed it and I have lived here for over 15 years.

[James Pallas]

Raymond, One more and I will get off the horse. The HE furnace is a good thing. All things have to be considered with these things. That dryer is electric but it is pushing air out of the room if it is properly vented to outside that has to be considered for proper venting. All of it acts together. And for you guys that have DC systems in your shop vented to another room and have a furnace and water heater in the shop your pushing 700 to 1200 cfm out of the room that that gas appliance may need. It may not be dust that is giving you that headache. OK I'm down off of old Blue now.
Jim

[Charlie Velasquez]

If it is in fact a vent for make-up air, close it up, patch the hole, and locate a more convenient spot to get the air. I really don't think the water heater and dryer care too much where they are getting the air. As long as they get enough air, they are happy. Add a decorative grill and you're good to go.

[Tim Hoyt]

I would be VERY cautious about sealing off the combustion air supply. It sounds like you have a regular old gas water heater that needs oxygen to support the flame. There might be enough air supply to support the water heater most of the time via other sources in the house ( a somewhat normal set-up). But get a clothes dryer going in the same room and you could have big problems. first you could be starving the water heater of an adequate oxygen supply, which can lead to poor performance and possibly an increased amount of carbon monoxide. And most importantly, you could have backdrafting. The dryer will suck air down the flu. then you get all of the flu gases into the room, which may include CO.
I second what an earlier commenter said; get a new heating contractor, the current one may get you killed.