Gas Hot Water Tank Air Intake Draft

[Mirx]

I have a natural gas Hot Water Tank that has an air intake vent next to the tank, but not attached. It’s a standard sized dryer-type pipe, maybe 4" diameter. This is in my partially finished basement, the pipe goes from the floor straight up to the basement ceiling, 90 degrees straight across the rec room roof and outside. Due to the cold air coming in, the temperature of water closet last night was -5C (23F). My basement temp was 18C (64F) when the main thermostat was set to 25C (77F). I suspect that this pipe may be the main source of the low temperature of my basement, since I'm inviting freezing cold air straight into the basement. I don't know much about the setup requirements for a natural gas Hot Water Tank, except that it does require this air intake. What can I do to limit this from freezing me out of my basement? Thanks.

[594tough]

A water heater needs a free flow of combustion air. Depending on how large the space where it is located is, it could require a fresh air inlet as you described. If the heater is not a power vent, a 4 " pipe sounds small unless there is a generally large source of air. The building code for your area set the ultimate requirements. If the 4" duct is necessary, and adequate, you migh investigate an air to air heat exchanger. Also, you mich investigate installing a direct vent heater, where the intake air goes directly to combustion and not to general room air.

[Mirx]

The water heater is inside a roughly built closet, about 4ft by 4ft, I can see into the storage room threw the corner of the water tank closet, because of the quick and easy way it was build by the previous owner, so it’s not exactly an airtight room, also the ceiling is unfinished, so air flows freely threw the rafters from room to room in the basement because of this, although I plan to finish off the ceiling. I have a natural gas forced hot air furnace located about 4 ft away from the water tank closet, the furnace is also in its own closet, maybe about 5ft by 5ft. The furnace closet walls are finished better than the water closet walls. There are no gaps threw the walls, just air flow threw the ceiling rafters. So it may have an air intake of its own somewhere, but its not immediately obvious, I may not be seeing it because of all the other furnace duct work. The air pipe in questions isn’t located in such a place that it would be supplying fresh air to the furnace. It does make me wonder how the furnace is getting an air supply to burn the gas, without having the same problem as the hot water tank.

What is a power vent, one that the water tank would control automatically? This would still bring in some could air though wouldn’t it?
Would the furnace be running off of a direct vent heater?
An air to air heat exchanger sounds like it may be a more expensive solution than a direct vent, but I can’t say for sure

[594tough]

Based on your descripition, it looks like you do not have proper combustion air, although it may be working because of the gaps at the walls and at the rafters. For a 40,000 BTU WH you need TWO vent inlets each a minimum of 100 square inches , allowing free flow of air inlet from the open areas of the structure. One vent within 12 inches of the floor, one within 12 inches of the ceiling. If you have a mix of combustion air from outside and inside the structure, the calculations are different. Before you finish the walls and ceilings down there, you need to get a local inspector or a good contractor to figure out what is required.

As far as keeping cold air out, I think we are back to the direct vent idea.