gas water heater vent routing--too many turns???

Old 07-14-07, 09:48 AM
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gas water heater vent routing--too many turns???

I just replaced a natural gas water heater and reconnected the vent pipe to the main vent from the furnace (just as the original water heater had been connected). Vertically from water heater to main vent, the vent pipe has adequate upward pitch (more than minimum 1/4" per foot). However, horizontally, the pipe follows a sort of S-shaped path.

Question: is that S-shaped path acceptable to an inspector? Just wondering if code allows that or if that would be seen as causing too much disturbance to the flow of the combustion gases.

Here are a couple photos of the vent...
view from side: <>
view from below: <>

Old 07-14-07, 12:02 PM
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I can't see any reason why you couldn't shorten that straight piece and bring the whole assembly into a straighter alignment.

Also, I suggest that you remove the foam from around the T&P valve and pipe its discharge to a safe location. Your local codes will dictate what safe means and may also require seismic (earthquake) restraints to the tank and flexible connections for the water and gas piping.

I would also prefer to see type B venting used rather than the single wall, again your local code needs to be followed.
Old 07-14-07, 12:34 PM
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Im with furd. Id check what code calls for there for sure.
As I see it no it will not pass here for sure. Foam on the T/P valve. The T/P valve not piped to the outside of the home or sewer. Then the vent from the water heater tied into the vent pipe of the furnace. It should go in to the flue pipe going out. I cant tell, but the flue has to be a B vent pipe going out and the right size to take both the furnace and the water heater vents. It dont look like it??????
Old 07-14-07, 04:42 PM
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While you're checking your local codes, I'd ask about the placement of the water heater under a stairwell with wood stairs.

Just a thought...
Old 07-14-07, 08:13 PM
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I'm guessing that piece of foam came with the WH, as probably did a couple of pieces for the hot and cold pipes, which he did not install. The mfg. does this to get an extra point or two on the energy rating to comply with federal specs.

The straight section from the WH appears to have an incorrect male/female alignment on the upper end. This would not be allowed. Each joint, including all the elbows, must be secured with sheet metal screws. I do not see any. Finally, all that single wall stuff must maintain minumum 6" clearance to combustible material . In the pictures, it does not look like it complies with this spec.

Bottom line, the inspector ( you ARE going to call in an inspector as REQUIRED, right?) will have a field day.

I am going to assume you are not in California, and therefor are not required to have earthquake straps and flexible connectors..
Old 07-15-07, 06:32 AM
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Thanks for the suggestions. I should have mentioned that this WH is not yet fully hooked up and running--no gas connection yet. I did the plumbing connections myself but have a licensed contractor scheduled to do the gas connection. I have a pipe for the T/P valve but have not yet soldered the threaded adapter to the end--and this pipe will be directed to a drain pan below the WH. Permits have been pulled so this installation will ultimately be inspected. Not near California so no serious earthquake concerns. Original WH installation was under stairway (house built mid-60s) and a number of neighbors have identical layout--so I assume inspector would have no issue with this (knock on wood)--but I guess I could yet be informed otherwise. I have previously spoken with an inspector over the phone about WH requirements. Some of the issues mentioned in this thread were not specifically addressed so I will have to call him back and check.

The photos I linked to showed my initial vent mock-up using existing fittings with minimal change to the original vent configuration--before the old WH failed. No screws yet. The "s-curve" path was a result of the WH orientation on one end (the first elbow off the draft hood is square to a line thru the 2 water connections--just trying to maintain maximum clearance from both water pipes) and the existing wye fitting on the other end.

But I realize now there are a number of deficiencies and I plan to scrap all existing single-wall vent pipe between WH/furnace and existing B-vent chimney:
- since the WH draft hood is compatible with 3-in vent, replace 4-in single-wall vent fittings with 3-in B-vent fittings (WH is 40 gallon, 40,000 BTU)
- insert a 6-in long vertical section of B-vent between the WH draft hood and first elbow (original WH installation simply had an elbow fitted to the draft hood); but raising first elbow 6 inches from draft hood looks like it might be difficult to get a minimum upward pitch of 1/4-inch per foot between first elbow and wye
- replace single-wall tee and wye fittings with B-vent fittings (where WH exhaust meets furnace exhaust and connect to existing B-vent chimney)
- furnace: replace single wall vent fittings with B-vent fittings; refitting the furnace venting would allow me to rotate the wye fitting slightly toward the WH and allow for a straight run from the WH elbow to the wye (at the expense of a less free-flowing furnace vent by the addition of a 30-degree (or so) elbow)

Ed Imeduc: You mention that there might be an issue with the WH vent tied into the furnace vent. I guess I will have to look into this and be open to an alternative configuration different from the original. As far as sizing, the WH draft hood allows for 3-inch vent, the furnace vent connection is 4-inch (originally fitted with increaser to 5-inch), and the vertical flue to the roof is 5-inch B-vent.

Here is a photo of the WH vent, furnace vent and flue with intermediate connections removed: <>

Anyway, I need to determine local requirements Monday.


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