Venting Furnace & Hot Water

Old 02-17-04, 11:47 AM
Thread Starter
Join Date: Feb 2002
Posts: 27
Upvotes: 0
Received 0 Upvotes on 0 Posts
Post Venting Furnace & Hot Water

I have an old house with a brick unlined chimney - currently the oil furnace is vented through here. I want to replace my electric hot water heater and am getting conflicting advice about what can/can not be vented into the chimney.
First I was told that you could not have 2 fuels (ie. propane and oil) venting into the same chimney - so, the best option was to get an oil hot water heater, vent in chimney with furnace but have a by-pass switch so that both were not running/venting at the same time.
Second, I was told that it was OK to install a propane hot water heater and tap the 3 inch propane vent pipe into the 6 inch furnace vent pipe that goes into the chimney.

Now, I am not sure which way to go. Thanks in advance for your advice.
Old 02-20-04, 01:14 AM
rav12's Avatar
Join Date: Oct 2003
Location: California
Posts: 650
Upvotes: 0
Received 0 Upvotes on 0 Posts
1. You can have appliances buring gas and oil venting from the same vent. The gas code allows this. However, an appliance buring gas and a solid fuel cannot use the same vent.

2. This is determined from the venting tables and depends among other things input rating of the appliaces in BTU, whether fan assisted or not, type of vent pipe, length of connector rise etc. In other words more info is required to answer the second point.
Old 02-22-04, 07:16 PM
KField's Avatar
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,015
Upvotes: 0
Received 0 Upvotes on 0 Posts
If you can afford the oil fired water heater, I believe you will find it less expensive to feed than the LP gas one. As for the chimney stuff, the only way you would need a cut-out is if the chimney can't handle both units. I have only seen that a few times in 25 years so it probably won't happen to you. All you have to do is check draft after installing the water heater. If you still have a good draft (-.02 wc) over the fire with both units running, don't bother with the cut-out.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: