Adding walls with drywall and painting whole room?

[Matthew Maggy]

This is not a flip or anything. It's a duplex we're house hacking and the kitchen has a water heater out on the open. I built a wall with a door around it and have just finished putting up the drywall and am ready to mud.

The problem is, that the new wall, joins an 2 old walls and the ceiling, which are already painted and what not. I don't really want to have to paint the old walls and ceiling because of drywall tape & mud. Is there a way to seal, or mud the new drywall so that I don't have to tape and feather on the old walls and ceiling and then paint them?

I hate painting. 

[Matt R.]

Disclaimer: I am not a professional plumber.

If it's an electric water heater, this doesn't apply.

If it's a gas water heater... do you have a sufficient supply of combustion air to the closet you made?

The water heater manual will say something like "if the heater is installed in a room of X cubic feet or more, you don't have to do anything else; if it's smaller than that, you need vent openings of Y square inches each".  Sometimes you can bring a vent pipe in from the attic.  Otherwise, you can install a couple of sets of louvers in the walls or door to the water heater room - one down low, one up high.  Or, use a louvered door. Louvers or louvered doors, bought new, will say how many square inches of open area they provide.

It is best to get the manual for the exact heater you have from the manufacturer, but if you can't, look at a current similar water heater at the hardware store (size in gallons, fuel, efficiency level) and get the manual for that one.

I used to live in a house where the water heater was in a closet behind the laundry room.  It had the normal double-wall metal vent pipe going up out of the top of the heater, through the attic, and through the roof to the outside.  But there was also a piece of single-wall vent pipe that went from the attic down to within about a foot of the floor in the water heater closet.  This second vent pipe provided air to burn with the gas.  Without it, the water heater could conceivably use up all the air in the closet, and either go out, or burn incompletely, creating carbon monoxide.

In my current house, the water heater is in the laundry room in the basement, and if I shut the door to the laundry room, the room is "too small" according to the specs.  My short-term workaround is to not close the door to the laundry room.  Long term, I plan to install a couple of air grilles (like a return grill for a furnace or A/C) on both sides of the wall next to the door, and make up a 4" long sheet metal "duct" to join the grilles.