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Improperly-vented gas fired water heater in a Minneapolis home (C) Daniel FriedmanGas Water Heater Vent Code & Standard FAQs
Q&A water heater venting codes

FAQs on venting requirements for gas-fueled water heaters:

This article series describes proper ventilation details for handling the exhaust from gas fueled water heaters, both LPG or propane and natural gas.

The natural gas fueled water heater shown at page top is improperly vented, lacking the recommended minimum 12" of vertical rise before the elbow and vented directly into a large masonry flue where it cannot develop adequate draft. This heater installation may be unsafe.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Q&A on Proper & Safe Exhaust Vent Codes & Standards for Gas Fired Water Heaters

These questions & answers about codes & standards for Venting Gas Fired Water Heaters were posted originally at GAS FIRED WATER HEATER VENTING CODES - be sure to review the codes and standards given there.

Watch out: for safety, water heaters must be vented using a listed and approved venting system that provides adequate size, height, and draft.

On 2020-11-07 by (mod) - requirments for venting a gas water heater in valencia county new mexico

Louis:

With a few small exceptions New Mexico has adopted the Uniform Plumbing Code or UPC.

For a PDF copy please see CHIMNEY CODES & STANDARDS inspectapedia.com/Design/COPIES-of-BUILDING-CODES.php#Chimneys

Here are direct links to

The NEW MEXICO MECHANICAL CODE (2015) http://164.64.110.134/parts/title14/14.009.0002.html

and

The NEW MEXICO PLUMBING CODE (2015) http://164.64.110.134/parts/title14/14.008.0002.html

On 2020-11-07 by louis chavez

what are the requirments for venting a gas water heater in valencia county new mexico

On 2020-11-06 by (mod) - requirements for a double-walled gas water heater vent pipe when exiting through the gable?

Stephen

If we're discussing a B-vent metal chimney (your "double walled vent pipe") then the manufacturer as well as chimney codes will almost certainly expect you to extend the chimney up to the require height above the roof.

We organize the details of these chimneys and their requirements starting at

TYPE B-VENT CHIMNEYS - home https://inspectapedia.com/chimneys/B-Vent-Chimneys.php

On 2020-11-06 by StephenNOLA

What are the requirements for a double-walled vent pipe when exiting through the gable? How far does it need to extend past the wall and/or roofline above? Does it need a 90-degree bend in pipe with cap? If there are gas water heater vented through separate pipes, what is the spacing requirements between the pipes, if any?

On 2020-10-23 by (mod) - To 'seal' a hot water flu vent pipe where it runs through the roof

Mark:

If you are sealing a gas fired water heater flue and are so far away from the heater (presumably on a basement or first floor) as to be at the roof, then sealing a metal flue joint with foil tape ought not cause an issue; I'm not sure why that's needed if you're using a UL-listed B-vent as those sections normally lock together.

On 2020-10-22 by Mark

To 'seal' a hot water flu vent pipe where it runs through the roof may I safely use a 3M foil tape with the temperature rating of either 225 degrees Fahrenheit or 300° f? Or, wood the heat of flue vent pipe make that foil tape into a combustible product? Thank you!

On 2020-09-25 - by (mod) - need a B-vent that extends sufficiently above the roof

Tom,

Typically you need a B-vent that extends sufficiently above the roof

TYPE B-VENT CHIMNEYS describes that material, and links at the end of that article address necessary height.

On 2020-09-25 7 by Tom..

Thank you ...I will need to find out the proper materials and height...at the moment, I don't know....

On 2020-09-25 - by (mod) - vent a standard gas water heater horizontally through the sidewall of house provided

Tom

You can vent a standard gas water heater horizontally through the sidewall of house provided it's venting to a chimney of proper materials and height OR it is connected to an approved direct vent system.

The proper chimney material and height are absolutely critical.

Watch out: The danger if you simply vented a conventional water heater exhaust straight out through the wall and stopped, or stopped with a short stub of a chimney is that you would have inadequate draft. In turn that risks dumping fatal carbon monoxide into the building - which could kill someone.

On 2020-09-25 by tom

forgot to mention it is a Gas heater

can I vent a standard type water heater thru the side of house

On 2020-09-08 - by (mod) - small test instrument hole in a water heater flue or vent is not unsafe

That hole is punctured or drilled in an exhaust flue vent connector by the heating service technician in order to permit the insertion of test instruments that are used at the time of service or maintenance.

It's not a safety concern though you could, if you like, cover it with a bit of aluminum-foil adhesive tape like the 3M product I show below.

Many technicians simply stick a short bolt into the opening.

On 2020-09-07 by Christina

I just discovered these holes in the venting/ chimney of my hot water heater. The chimney sleeve doesn’t cover the two bottom holes, and then there is seemingly a man made hole in the chimney itself. Is this a risk of improper ventilation?

On 2020-09-02 - by (mod) - What is the horizontal run on a vent

Patrick,

You're going to want to find the manufacturer's installation specifications for your specific water heater brand and model. The manufacturer will tell you the maximum horizontal run that they allow. It's not the same for all products.

On 2020-09-01 by Patrick

What is the horizontal run on a vent

On 2020-08-05 by Joe

Ok do you have to replace the existing 3 inch single wall vent pipe with a 4 inch pipe when replacing a gas fired water heater? The existing 3 inch pipe run is from basement and terminates on the roof.

On 2020-07-23 by (mod) - Can I a vent system be installed which has a 3’ elevation drop be corrected by adding an in-line fan?

Yes you can add a power vent system where necessary, provided your water heater manufacturer approves.

Watch out: A more-subtle concern is creating excessive draft that causes improper gas water heater operation that could then be unsafe.

On 2020-07-23 by Denny

Can a vent system be installed which has a 3’ elevation drop be corrected by adding an in-line fan?

On 2020-07-03 - by (mod) - backdraft issues when sharing a chimney with a natural draft water heater and a fan assisted furnace

Pamela

Because one of the units is fan assist and one is natural draft, they should be joined together in the chimney, and not before they enter the chimney which is what the installer did

That sounds important to me.

Watch out: But lets get someone to actually measure the draft so we can get past the speculation - othwerwise your heating system is unsafe and risks dangerous carbon monoxide poisoning or an over-draft that causes the water heater to work improperly.

On 2020-07-02 by Pamela Nardone

Hi, I live in NJ and had backdraft issues with the venting of my fan assist 140,000 BTU gas furnace and 50 gallon 40,000 BTU gas natural draft water heater. We had a Forever Flex 30' 5" liner installed, and I have been smelling fumes in my home ever since. The installing company insists they put the correct liner in.

I had an inspection by a certified chimney inspector, and he said the liner should be 6". He also said that becasue one of the units is fan assist and one is natural draft, they should be joined together in the chimney, and not before they enter the chimney which is what the installer did. Previously, they were joined in the chimney.

I obtained a permit for this work and had it inspected, but there seems to be a difference of opinion.

All I know is I smell fumes, and I shouldn't. Now my water heater is leaking, and my plumber wants the venting issues fixed before he installs. Any help would be greatly appreciated. Thank you.

On 2020-05-24 - by (mod) - hot water tank is vented through my chimney and it is falling apart,

Any chimney that's passing up the outside of a house needs to vent two feet above the Ridgeline if it comes out at the ridge or at the other chimney height requirements you'll see by searching inspectapedia..Com for chimney height.

You also need to consider that if you are just venting a water heater it may not vent safely through a tall exterior single wall or all metal flue. Check the installation instructions for your specific water heater brand and model.

You want to look at a metal chimney like a "B-vent" for gas fired water heaters.

On 2020-05-24 by Tony

My hot water tank is vented through my chimney and it is falling apart, it’s at the side of my house how far up from the roof can I go with the pipe because I’m taking the chimney down below the roof and I’m not going to build it back up

The hot water tank is the only thing the chimney is using

On 2020-05-08 - by (mod) - exterior installed direct vent water heater venting near an openable door or window

Rob,

GAS APPLIANCE / HEATER DIRECT VENT CLEARANCES

gives the required distances

Thank you for asking and for the safety question. You'll see there we have an entire but separate article on that topic. Don't hesitate to post follow-up questions or comments.

On 2020-05-07 2 by Rob S.

What are the requirments for an exterior installed direct vent water heater venting near an openable door or window of a dwelling unit? I could not find anything in the CPC regarding this.

On 2020-04-30 - by (mod) -

I would identify the brands involved and ask the manufacturer for a listed, approved connector.

On 2020-04-30 by Geoff

thanks for the response. That's the first part of my ask. I guess the second part is can you transition flexible chimney liner to rigid b-vent to make the 10' connection from where the chimney now ends to where the existing furnace vent pipe goes through the roof.

On 2020-04-30 - by (mod) - possible to share a flue with two gas fueled appliances?

Geoff

Forgive you but I am a little confused about this question.

If you're asking whether it's possible to share a flue with two gas fueled appliances, the general answer is yes provided the vent has adequate capacity.

On 2020-04-30 0 by Geoff M.

Draft venting water heater in basement venting stainless liner in chimney.

Chimney was taken down below roof line and roof sealed. Is it possible to connect liner to rigid b-vent in attic (seal top of chimney around connection with metal flashing/cap) and wye into existing furnace (in attic) b-vent through roof approximately 10 feet away from chimney entrance point in attic?

On 2020-04-05 - by (mod) - route some metal chimney types out through a building side wall and then up above the roof line.

It's possible to route some metal chimney types out through a building side wall and then up above the roof line.

There are also high-efficiency condensing gas fired heaters that vent at a simple sidewall vent with no chimney.

From your photo I can't say what equipment is installed.

On 2020-04-05 by Ceecee18

Sorry. I’m seeing images of non direct venting that are straight out the wall so it’s confusing. As noted, 4yr old gas furnace vent pipes run straight across walk out basement and out the rear wall, just below the window. Thanks.

On 2020-04-05 - by (mod) -

If your prior chimney didn't extend above the roof line by at least 2 feet from nearest point of contact then it was improper and unsafe.

On 2020-04-05 by Ceecee18

Tree took down out heater pipe (side vent thru single block wall/exterior stucco). Plumber who installed heater 7yrs ago now says we're out of code & quoted $3-4K to replace pipe but I think that's wrong.

The photo is taken from is almost directly above gas furnace intake/exhaust pipes. PA code reads min 10ft from lot line (done) & 10ft above nearest grade (~10ft). Prior chimney never exceeded roofline. Sorry -- photo thru a screen.

On 2020-03-29 - by (mod) - horizontal vent for gas water heater?

Darrold:

What is the horizontal venting distance?
What do the manufacturer's installation instructions say about venting the new water heater?

I worry that the distance is great enough that the prior unit would not vent properly and needed a vent booster fan.

Watch out: when a water heater can't vent properly there is risk of fatal carbon monoxide poisoning.

On 2020-03-28 by Darrold

I have a rheen 73 gallon Natural gas water heater I have it plumbed in I need to horizontally vent the old one had exhaust fan that plugged into water heater the new one has no fan can I just use metal to vent to outside?

On 2020-03-18 - by (mod) - cold single wall metal vents may not vent the water heater properly

George

Watch out: Even if you don't face a fire hazard, a single wall vent might, for some heaters, be too cold and thus the heater might not vent properly in some climates/locations.

Let's start by identifying the brand and model of your water heater, then take a look at the installation manual for that specific heater - as the manufacturer's word will be authoritative.

On 2020-03-18 by George

In the process of replacing 40 gal gas water heater. I have had 3 plumbers come due to well....some lacking professionalism among other things. Today I was told the vent pipe needed to be replaced. They stated it was not code to use single wall vent pipe.

The only issue I have with that statement is, the vent pipe runs from water heater up and over about 2 1/2 feet through cinder block wall to exterior.

The entire vent pipe is on the exterior besides the entrance through exterior cinder block wall. I can’t seem to find information saying this is not up to code. I understand it would need to be double wall if used on interior....any thoughts?

On 2019-11-11 - by (mod) - vent gas water heater out through side wall with PVC?

Watch out: No. Venting a conventional or typical gas fired water heater straight out through a sidewall using plastic pipe would be failure to follow the manufacturer's instructions and most likely would be unsafe.

On 2019-11-07 by Harry

Can I vent a gas water heater designed to be exhausted through PVC pipe out the side of the house up the chimney that my furnace exhausts from?

On 2019-05-08 - by (mod) - gas water heater be placed in a small closet?

Bill,

I don't know about your specific water heater as we don't know it's brand and model, but there are some gas fired water heaters approved for installation in a closet or similar small area such as some mobile home or trailer heaters.

Watch out: Of course you need to provide combustion air. And you don't want a gas water heater that can vent into or consume oxygen from a sleeping area.

On 2019-05-08 by Bill

Can our gas water heater be placed in a small closet?

On 2019-04-26 - by (mod) - support brackets for flue vent pipes and metal chimneys

Jim

Indeed there are steel brackets that are sold for securing metal chimneys and vent pipes to building walls. If you need to hang from overhead you may find the length of perforated steel strapping will also be adequate.

Remember also check your fire clearance distances.

On 2019-04-26 by Jim Bunton

how do I support the double walled vent pipe? do they make some type of bracket? Thank you for the article, very helpful

Question: what's the purpose of these fins on the gas water heater flue?

Fins on gas water heater vent extract heat to surrounding area, possible subtle safety hazard (C) InspectApedia.com MHI have never seen this on a gas fired water heater, can you tell me what the heck it is? - Anonymous by private email 2019/01/23

Reply: "energy savings" or heat extraction fins on a gas water heater: Safety hazards

Those fins on the exhaust vent were popular starting in North America during the Arab oil embargo in the 1970s and are still sold and installed on occasion.

The function of these fins on the gas water heater flue vent connector is to try to increase the transfer of heat from the water heater exhaust into the surrounding area - maybe to make it warmer, in a fantasy that we're cutting heating cost by exracting heat, perhaps in hope of preventing frozen pipes nearby.

Watch out: There is in my OPINION (there's no authoritative data I've found on this ) a subtle potential safety hazard of the heat transfer fin add-on.

**IF** the gas fired water heater is already venting into a chimney flue that is big, and perhaps sometimes cold (as in old buildings) and perhaps tall, THEN the heater may have trouble venting under all weather conditions, risking back-drafting and carbon monoxide poisoning hazards in the building.

That problem could be present with or without the heat transfer fins but would be exacerbated by the additional heat that the fins remove.

If there were any doubt about the chimney it would merit inspection by a certified chimney sweep, a check for signs of back-drafting. You probably already know those signs.

Thanks for the photo and question.

Watch out: reader MikeJC adds these additional safety hazards at your water heater:

On the photo with fins on vent pipe, that installation does not meet code for two reasons:

See also these examples of heat recovery methods using fins or devices attached to flue vents or other heater tuves:

On 2020-04-25 - by (mod) - gas fueled appliances vents and chimneys must slope up not down

... Typical water heater draft hood at InspectApedia.com

Not really, Monte.

Forcing a gravity-vented gas-fired water heater to vent "down" is defying gravity, impeding the draft, and risking dumping fatal carbon monoxide gas into the building.

Solutions:

- a shorter water heater

- moving the chimney flue vent connector thimble up higher (watch fire clearances from nearby wood or other combustibles)
or

- (only if the heater manufacturer agrees it's safe ) using a power venting system

Frankly if my water heater vent connection to the chimney sloped down 1/4" across a foot or two I'd not panic, but from your description, if the outlet at the top of the water heater is 49 1/2" above the floor you cannot possibly connect it safely to a chimney opening whose bottom is essentially at 50 inches, because you still need the additional height of the draft hood and the height required for the 90 degree elbow to make the bend to head over to the chimney.

You can see from this example of a 3-inch diameter metal flue vent 90 degree elbow from PelletVent that the elbow alone is going to need more than 5 1/2" of height to make the bend from vertical to horizontal - actually it's more like a total of 7" from the top of the heater.

Add to that the height of the draft hood,

On 2020-04-25 - by (mod) -

Not really, Monte.

Forcing a gravity-vented gas-fired water heater to vent "down" is defying gravity, impeding the draft, and risking dumping fatal carbon monoxide gas into the building.

Solutions:

- a shorter water heater
- moving the chimney flue vent connector thimble up higher (watch fire clearances from nearby wood or other combustibles)
or
- (only if the heater manufacturer agrees it's safe ) using a power venting system

Frankly if my water heater vent connection to the chimney sloped down 1/4" across a foot or two I'd not panic, but from your description, if the outlet at the top of the water heater is 49 1/2" above the floor you cannot possibly connect it safely to a chimney opening whose bottom is essentially at 50 inches, because you still need the additional height of the draft hood and the height required for the 90 degree elbow to make the bend to head over to the chimney.

On 2020-04-25 by Monte

If I install a gas hot water heater that has the outlet flue at 49 and one-half inches above the floor, can I attach to a chimney flue that opens at 50 inches above the floor? The connecting pipe would be tipped slightly down going to the chimney.

On 2020-03-10 - by (mod) - clearance to combustibles for gas heater venting

You could (better) of course ask Reem directly, but my interpretation is that 1-inch clearance to combustibles means just that - 1inch throughout the routing of the vent.

On 2020-03-10 by EngineerJohn

Do I need to maintain 1 inch clearance to combustibles in a vertical wall for a direct vented gas conventional water heater installed in a full basement that uses 3"/5" concentric double walled metal vent pipe through the floor, vertical wall, and ceiling?

On 2020-01-08 - by (mod) - water heater height off of floor

Dave

There's no single "right" answer to gas water heater height requirements.

If the heater is located in a garage, most codes want it elevated 18" above the level of the garage floor.

In other locations, such as a concrete slab basement, the heater may sit right on the slab.

In some jurisdictions the local code official (city, town, county) may want a drip pan under the heater.

On 2020-01-08 by Dave

How far off the floor do I need to raise a gas water in Oregon?
Or do I need to raise it??

On 2019-09-16 - by (mod) -

If you are describing a gas fueled water heater that is not vented to the outside, that is unsafe.

That's more basic and immediate concern then the assignment of to code or not to code.

The cost to cure should be trivial compared with the value of a home. It might be that you want to fix it immediately for your own safety.

On 2019-09-16 by Tom

Hi, I am selling home with original water heater (1988). Buyers want exhaust/ vent pipe replaced because it is not "code". Have code requirements changed since installation and am I required to do modifications?

On 2019-07-13 - by (mod) - venting a Tkagi tankless water heater

Let's get the model number of the water heater - then we can make an authoritative remark or two by seeing what the manufacturer permits for that specific heater.

I agree that dryer duct, per se, is not likely to be proper nor safe. But there might be a flexible metallic vent pipe rated for use with gas heaters that could be ok.

On 2019-07-13 by davidponter

my son had a Tkagi tankless water heater installed what kind of venting should he have it looks like dryer venting was used

On 2019-04-26 by (mod) - steel brackets that are sold for securing metal chimneys and vent pipes to building walls.

Gas water heater venting up through a roof  at InspectApedia.com excerpted from Whirlpool gas water heater manual cited in this articleJim

Indeed there are steel brackets that are sold for securing metal chimneys and vent pipes to building walls. If you need to hang from overhead you may find the length of perforated steel strapping will also be adequate.

Remember also check your fire clearance distances.

On 2019-04-26 by Jim Bunton

how do I support the double walled vent pipe? do they make some type of bracket? Thank you for the article, very helpful

On 2019-03-02 by (mod) - Is a ULN natural gas water heater required for Chatsworth,CA.

Gurb

I am doubtful that any communities in California dictate the kind of water heater that you are permitted to install.

On 2019-03-01 by Gurbux Singh

I an ULN natural gas water heater required for Chatsworth,CA.?

On 2019-02-23 by (mod) -

Sorry but i don't understand the situation.

Certainly without combustion air the heater would be unsafe, risking fatal carbon monoxide poisoning

On 2019-02-22 by Judy

I have a gas hot water tank and there is a big dent on the floor which brings him lots of cold air does that have to be left open or can I cover it

On 2019-01-24 by (mod) -

Chris

Probably not. Any obstruction close to the exhaust vent risks of fatal carbon monoxide Hazard inside and other improper operation of your heater.

the wind problem is one that's been reported before. And in fact we have an article on the topic here at inspectapedia.

Sometimes we can create a Wind Block that's sufficient distance away that the manufacturer will accept it.

Let's get the brand and model of your direct vent system and see what the manufacturer considers safe.

PLEASE see this article

DIRECT VENT WIND PROBLEMS

where we address your question in more-detail

On 2019-01-23 by Chris Hodge

I have a gas water heater vented through a side wall. When the wind blows through the vent it blows out the pilot light. Is it safe and to code to place a vent cover on the outside end of the vent?

On 2018-11-15 by Anonymous

What is the correct distance between the bottom of the cone vent to the top of the hot water heater

On 2018-11-13 by Brian

Thanks so much for the info.....this is very helpful. I will only be painting the vent above the roof boot and the vent cap.
I will paint the vent above the roof line, which will reasonably be below 350 degF with metal primer as you suggested
and plain common Rust-Oleum paint.

I would hope that this finish (primer/finish coat) would not blister with temperatures under 350 degF.

That was my main concern that the paint might blister or even for that matter catch on fire.
Thank you so much for all your detailed advice.

On 2018-11-13 by (mod) - Rust-Oleum high temperature-resistant paint

Brian

The Rust-Oleum high temperature-resistant paint that I've used was a spray-on engine paint that bakes in to a durable finish beginning at 600 degrees F.

At the hottest point in a gas water heater flue - the flue-vent-connector right above the heater top - the temperature is not likely to rise above 350 degF.

It is reasonable to assume that higher in the flue temperatures are much lower. Not only do you thus not need a high temperature paint above the rooftop, but the high temperature paint may fail from not having ever reached a temperature high enough to "bake it" in to durable form.

Watch out however: if you are spraying a typical B-vent, until the surface has weathered and oxidized a bit the paint is not likely to remain adhered. Before painting a new galvanized steel such as at a B-vent chimney top I would

1. lightly wire-brush the surface

2. wipe down the surface with vinegar to give a slight etch to the surface

3. clean all that off and let the surface dry

4. paint it, perhaps first with a metal primer then the finish coat.

If your metal chimney is stainless steel you should eschew painting it at all as the paint won't adhere and the chimney will look horrible.

On 2018-11-13 by Brian

Do you need high heat resistant paint for the vent pipe from the roof boot to the vent cap (including metal cap) on on the roof.
Example: Rustoleum high heat paint or engine enamel. Does the vent stack get that hot outside?

On 2018-10-22 by (mod) - extending the vent pipe higher at a mobil ehome

Steve,

Thank you for an interesting question.

It's possible that extending the vent pipe higher will help with the downdraft problem if that is in fact what's blowing out your pilot. It's also possible that the cap on top of that metal chimney is not the proper one or is not properly designed to stop downdrafts.

On 2018-10-22 by steve

i have a mobile home home with a natural gas hot water heater that goes out on windy days. my vent pipe extends about 2 feet above roof and has a round cap on it. it does not appear to be as high as the peak of the house. could this be the reason the water heater goes out on windy days and what can i do to correct the problem. thank you


...

Continue reading at GAS FIRED WATER HEATER VENTING CODES - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Chimney & Water Heater Venting Articles

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GAS FIRED WATER HEATER VENTING CODE FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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