Hot water heaters that are fueled by gas need to be vented properly. One of the most common types of hot water heaters is the chimney vented style. So what is a chimney vent water heater?
A chimney vent water heater is simply a gas-fueled hot water heater that is vented through a chimney. Also referred to by the pros as an “atmospheric vent” water heater.
This type of hot water heater is by far the most common of all water heaters in a residential setting. If your home was built in the 1900’s and you have a chimney then most likely your water heater is vented through the chimney. On most new homes if you have a conventional vent gas water heater it could just be vented through a metal flue pipe and go out through the roof where it’s then terminated. More on that throughout this post.
Why do you need to vent the water heater?
Because when you burn gas or fossil fuel it creates combustion and exhaust gases that absolutely need to be vented properly to remove them from your home. When you have a hot water heater that runs on natural gas or liquid propane (LP) gas, your hot water heater will need to be vented properly. Of course, we recommend you check your hot water heaters specification sheet and install manual for your specific hot water heater venting requirements.
Not only do you have to follow the guidelines for venting the water heater in your basement but depending on what kind of water heater you have, the termination of the vent outside of your home as certain requirements as well – for example, the vent might have to be so far away from a window or corner of a home. However, if its chimney vented that won’t be an issue for you.
What is atmospheric venting?
Simply put it’s the process of the exhaust gases naturally rising into the atmosphere. The hot water heaters exhaust gases are channeled through a vent and rise into the Atmosphere. An atmospheric gas hot water heater actually vents through a metal pipe. The metal pipe goes from the top of your hot water heater and travels upward through your home. It then vents out the top of your roof where it is then terminated.
Since we know that hot air works on the principle of rising upward, that is exactly what the atmospheric vent is for. It is critical that the venting is channeling upward and if not totally vertical then sloping upward. By sloping upward it will ensure the gases are flowing out of the house and through the metal vent pipe.
It is my recommendation that you consult with a professional plumber or inspector for any local code questions. Remember safety is first!
What venting material is used on a chimney vented heater?
The venting material is a metal pipe that typically transitions into a chimney liner. The first few feet of venting material before it reaches the chimney is most likely going to be a single-wall metal vent pipe or even a “B vent” pipe.
A “B vent” is used for venting gas appliances. It’s a double-wall metal pipe. That means it has two layers – an outer wall and an inner wall. The double-wall “B vent” does three things:
1) It helps radiate the heat better
2) It doesn’t get as hot
3) It adds another layer to help keep any fumes or exhaust gases from leaking out
Normally you will see a ninety degree bend and then a section of straight metal pipe that leads into the chimney. The length will vary depending on how far away your chimney is from the hot water heater.
The size of that metal venting will be 3″ or 4″ in diameter depending on the water heater venting requirements. Once it reaches the chimney it’s then connected to either a “B vent” metal venting or a chimney liner that will travel all the way up the chimney and terminate at the top.
Functionality of the venting
Since the chimney vent, hot water heaters exhaust gases naturally rise and travel through the venting. The room air gets pulled in through the draft diverter that sits on top of the water heater. The venting then connects to the draft diverter. As the air travels through the venting it carries the exhaust gases with it. It then exits through the chimney and out the top.
Another reason contractors vent through the chimney is because sometimes that’s the best option. If you’re pressed for space, venting through the chimney makes the most sense. If you think about it, that’s one less hole coming out of your house. Who wants to see a bunch of roof terminations anyway. If you’re like me and value the aesthetics of your home you would appreciate that.
I’m sure if you have a chimney vented water heater you’ll see that the hot water heater itself is probably placed really close to the chimney, or at least as close to it as feasible. That just makes the most sense to have the heater’s footprint as close as possible to the chimney.
You wouldn’t really want the heater to be more than just a few feet away from your chimney. There’s nothing wrong with that, it’s just more pipe to run and more pipe in your basement. Which could just take up that precious basement space that we all need.
For the aesthetic and functionality of your mechanics, it makes the most sense to put the water heater as close as possible to the chimney. There’s a good chance your furnace is vented into your chimney as well.
Safety considerations
Venting gas appliances properly is very important. That starts with the install. If you have your water heater installed per the manufacture specs you will be good to go. Keeping your venting clear of any debris is also just as important. If you happen to have a missing flue cap or screen that can be an access point for debris and that can be a problem that you will want to address right away.
I’ve had many plumbers send me pictures of vent pipes that were severely clogged. Sometimes with just nesting debris and sometimes with dead squirrels or birds… it’s not a pretty picture.
This can cause major problems and pose a safety concern for you and your family. You see if the venting is blocked it will create a backdraft and then the exhaust gases will come back into the house. Having your chimney inspected every so often would be a good idea.
Have a carbon monoxide detector
It’s definitely a best practice to have a carbon monoxide detector in your basement and if possible on every level of your home. If there was ever an issue with your hot water heaters venting you would be alarmed by the carbon monoxide detector. I personally really like the combo ones that are a smoke detector and carbon monoxide detector in one.
The next time that you have a plumber over for any maintenance or plumbing project you could ask them to just check out your water heaters venting to ensure that it’s venting properly and that it’s clear of any debris. Their experts and should have no problem taking a look at that for you.
If you want to do a quick test to see if you’re getting proper venting flow. Just put your hand close to the draft diverter that’s on top of your water heater. You should feel the cool air being pulled up into the vent. If you feel warm air pushing out of the vent then that is a problem and you should call a professional plumber right away. The safety of yourself and your family is always the number one priority.
Lastly, I want to thank you for taking the time to learn about chimney vent water heaters and some of the venting options that apply to conventional atmospheric hot water heaters. Please consider taking a look at my other articles and please share this post if you think someone could benefit from this.