Water heater flue problem

Old 01-13-10, 03:30 PM
Thread Starter
Join Date: Jan 2010
Location: Nevada
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Water heater flue problem

The old gas-fired water heater in the basement was replaced with a new unit that is slightly taller. The 90 degree flue elbow now is mounted right at the outlet of the 4"draft hood and there is an 8 ft horizontal run before the flue goes vertical for two stories to exit on the roof. Never had a problem with the old draft hood, but now we have alot of flue gas "spill" before things heat up. Our carbon monoxide sensor went off.

Has anyone experienced this?
Can I use a larger bottom diameter draft hood?
Old 01-20-10, 06:41 AM
Sharp Advice's Avatar
Admin Emeritus
Join Date: Feb 1998
Location: The Shake and Bake State USA
Posts: 9,927
Upvotes: 0
Received 7 Upvotes on 6 Posts
Hello Karl61 and Welcome to our Do It Yourself Web Site and the Water Heaters topic.

Humm. Surprised there isn't any reply to your question already.... But you are correct about the condition of flue gases spilling at the down draft diverter.... and why the detector is alarming.

Flue pipes cannot contain any 90 degree elbows. Only angled elbows and the flue pipe must be a continuous up-wards angle or the condition you're experiencing will always occur.

Some how and in some way that 90 degree existing elbow has to be removed. Re-pipe flue to have a continuous upward incline and the current problem will be resolved.

In some states, counties or cities, flex metal flue tubing is legal. Inquire about that and other possible solutions with a plumber at any local plumbing supply store.

Not a BIG BOX store.... Rather at a plumbing parts supply store where plumbers obtain their supplies. Ask them how a plumber would resolve the problem and bring photos of the present condition for them or parts/supply sales rep to better visualize the current situation....

Beer 4U2
Old 01-24-10, 09:37 AM
Join Date: Nov 2004
Location: CA
Posts: 1,913
Upvotes: 0
Received 0 Upvotes on 0 Posts
Refer to the National Fuel Gas Code book for detailed instructions, but in general, the flue should not take a 90 directly at the draft hood. It should rise vertically about a foot before doing so.

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