Gas water heater installation question

[wdfifteen]

I have a electric water heater that I want to replace with a more efficient gas heater. Venting is going to be an issue because of its location.

It sits a couple of feet from an old chimney that is no longer in use. Could I punch a hole in the chimney and run the vent pipe up the flue? Is that legal?

[cabmandone]

As long as the pipe runs all the way up and exits the chimney through a cap it can be done. How long is the overall run to get it outside?

[dad911]

High efficiency water heaters are PVC now, ducted out the sidewall. Tankless have dropped in price also. Check the specs, need to be a few feet from windows that open, and intakes for other devices.

You don't want to use an old flue just for HW. Not enough BTUs to keep it heated, and under some conditions the gasses will drop into living space. (backdraft)

[cabmandone]

Originally Posted by dad911

High efficiency water heaters are PVC now, ducted out the sidewall. Tankless have dropped in price also. Check the specs, need to be a few feet from windows that open, and intakes for other devices.

You don't want to use an old flue just for HW. Not enough BTUs to keep it heated, and under some conditions the gasses will drop into living space.

I read it the same way but he's talking about running the pipe all the way up the chimney and exiting the way it looks.

As long as there's nothing venting into the chimney, the PVC "should" qualify as a liner and there should be no issue as far as code goes. My only concern would be the length of the vertical run and supporting it.

[wdfifteen]

It's about 30 feet running horizontally above a drop ceiling. It's a pain to get it up there.

[wdfifteen]

Originally Posted by dad911

You don't want to use an old flue just for HW. Not enough BTUs to keep it heated, and under some conditions the gasses will drop into living space. (backdraft)

I wouldn't consider just punching it through the wall of the chimney. It would have PVC all the way up to free air.

[cabmandone]

Like I said in my edit, My only concern would be supporting the vertical run. That seems like a lot of pressure to put on an unsupported 90% elbow where you'd exit the chimney to run to the water heater. Probably 3" PVC due to the length of the run either way?

[Cajundaddy]

I would not use an existing chimney. It would be fairly simple to relocate anywhere you can get good venting and a properly sized gas line and then run your water line to it. The more centralized to your kitchen and master bath the better.

[dad911]

Originally Posted by wdfifteen

I wouldn't consider just punching it through the wall of the chimney. It would have PVC all the way up to free air.

Got it.

Then yes. Most instructions I've seen need two elbows out the roof, so exhaust points down. Sometimes they spec an acceptable alternate termination. There is a max length specific to water heater and pipe size, then subtract for elbows. Last one I looked at as I recall was a bradford white, and it was 40' then subtract 5' for each 90.

[dad911]

Originally Posted by cabmando

Like I said in my edit, My only concern would be supporting the vertical run. That seems like a lot of pressure to put on an unsupported 90% elbow where you'd exit the chimney to run to the water heater. Probably 3" PVC due to the length of the run either way?

single story or 2?

[Dpmulvan]

You can buy a stainless steel venting kit made for running up a chimney. You don’t want to vent your heater directly into the chimney for various reasons. Condensation, the low heat from energy efficient hot water heaters might night rise out of chimney due to low temp of gases, condensate can damage your chimneys mortar, drafting dynamics of chimney could cause carbon monoxide issues in your home.
Buy the kit and do it to code.

[Dpmulvan]

[GH85Carrera]

Just double check the code for high off the ground the gas water heater has to be. It is getting crazy around here. Mine is on a huge support in a special closet just for the water heater in the garage. I guess if your water heater in in the house it is less of an issue.

The pan under the heater has to have a separate drain of it's own. Ours goes along the garage wall through a outside wall, and would dump into the flower garden in case of a leak.

[cabmandone]

^^^
We live in Ohio. They don't much care what we do as homeowners. Most areas have no code inspection and even if there is code inspection, no one reports a water heater change out so that it can be inspected.

[wdfifteen]

How far away from windows does the vent need to be?

I might be able to replace the water heater in the east end of the house (instead of the one in the west end) if there is enough wall space between these two windows. They are 20 feet apart and about 3 1/2 feet above the band board. The vent would have to come through the band board.

[wdfifteen]

Originally Posted by cabmando

^^^
We live in Ohio. They don't much care what we do as homeowners. Most areas have no code inspection and even if there is code inspection, no one reports a water heater change out so that it can be inspected.

True in some counties. When I lived in Greene county they were all over you. Out here in the sticks you can do about anything.

[john70t]

Originally Posted by Dpmulvan

Condensation, the low heat from energy efficient hot water heaters might night rise out of chimney due to low temp of gases, condensate can damage your chimneys mortar, drafting dynamics of chimney could cause carbon monoxide issues in your home.

My WH only has a 8' power vent run to outside but I've had foot-long ice bridges created to the ground which had to be knocked off.
(stock internet pic)

[cabmandone]

Patrick,
IIRC it's 24" to a window. You could go between those two pictured easily and safely. Your only grief might be cleanly making the hole through the bricks.

[dad911]

This was the diagram that came with my Rinnai tankless. Others will be different. You have plenty of room between those windows.




In my case 'B' is 12 inches, yet local inspectors question less than 36"

[wdfifteen]

Thanks for the replies.
This is part of my plan to prepare for the apocalypse. I'm replacing one of the electric water heaters with a gas heater and running separate circuits to the refrigerator and freezers that will be wired into a transfer switch. Getting a 7500 watt generator to keep the freezers and some other things going in case of a power outage. Too bad our DSL service goes down the minute the power goes out.