Clearance For Hot Water Heater Flue. - Plumbing - DIY Home Improvement | DIYChatroom

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Plumbing


Thread Tools Display Modes
Old 05-29-2009, 12:04 PM   #1
Join Date: May 2009
Location: SE Wisconsin
Posts: 36
Rewards Points: 27

Clearance for hot water heater flue.

I'm building a room in my basement and one of the walls will be right next to my gas water heater. What type of clearance do I need to keep combustible material (studs) from the metal flue. It gets pretty hot to the touch.



jailbird371 is offline   Reply With Quote
Old 05-29-2009, 01:36 PM   #2
Registered User
Termite's Avatar
Join Date: Apr 2008
Posts: 6,520
Rewards Points: 2,000

Type B (double wall) gas vent requires minimum 1" to combustibles. Single wall flues (what comes up from the water heater in most cases) require more....Can't remember exactly because it rarely comes up but for some reason I'm thinking 4".

If you're enclosing the fuel-burning appliance(s) in a small room then you also probably need to provide combustion air ventilation as well. It is a definite BIG safety concern and a lot of people don't think about it when finishing basement space. For every 1000 btu/h's of input rating on the water heater and the furnace (unless the furnace pulls air from outdoors) you need 50 cubic feet of space in the mechanical room.
For example, a 40,000 btu/h water heater alone needs 2000 cubic feet of room space just to provide it enough air for combustion. That's 50cf x 40 (btuh's x 1000)= 2000cf.


Termite is offline   Reply With Quote
Old 07-05-2009, 09:04 PM   #3
Join Date: May 2009
Location: SE Wisconsin
Posts: 36
Rewards Points: 27

Right now there is a single walled vent leading up to the floor and then goes to a double wall up through the house. Sounds like it would be best to use double for the whole thing.

Anyone else know if it is indeed 4".
jailbird371 is offline   Reply With Quote
Old 07-05-2009, 10:04 PM   #4
Registered User
Join Date: Mar 2009
Posts: 11,730
Rewards Points: 526

If only the one gas unit: Size--minimum or 3"diameter...........IRC T2427.2(1) UMC 808.0
No single wall in attic or cold or concealed space2426.7.6 815.1
Sheet metal screws to appl. vent collar 2426.10.7 815.1
(three sheet metal screws at connection to vent 2426.10.12 815.1

Minimum clearance to combustible for single wall is 6 inches T2426.7.7 T3-3
Single wall may not pass through floor or wall 2426.10.15 815.2.2.6
3in.-dia. connector OK to 4in.-dia.flue collar if fan assisted appliance and vent height is >10 ft. 2427.2.2
Connector not >two sizes larger than flue collar 2427.2.10

Be safe, G
Gary in WA is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Kitchen Faucet Cold Water Runs Hot Mthrboard Plumbing 8 08-02-2009 06:59 AM
Natural Gas Water Heater Leaking from Release Valve Pipe? psumike Plumbing 6 01-14-2009 07:18 PM
Water heater flue advice... skipjack Plumbing 2 08-18-2008 05:25 PM
How to Space Water Heater Flue Vent from Outside Wall? austinbirdman Plumbing 1 03-12-2007 10:28 AM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1