The following information does not apply to a tankless type water heater power vent systems.
PVC vent pipes can be used only with water heater power vent /exhaust motor equipped hot water heaters also known as an induced draft gas water heaters.
The following information may also apply to CPVC and ABS pipes if such installations are permitted by the manufacturer and local authorities. Check water heater inspection for more information about water heater installations.
For the rest of this post I’ll be using “PVC vent pipe” just to make it easier. When installing a new or altering your existing water heater vent pipe installation, always check your particular water heater model for the manufacturer requirements and verify installation with local jurisdiction authorities.
There are two types of PVC pipe water heater power vent systems – single (single wall and concentric) and double pipe.
Power vent equipped water heater discharges exhaust gases through that single pipe. However, requires combustion air for fuel burning process and this must be supplied in sufficient amounts from the house interior or exterior.
You cannot install the water heater power vent system that uses just a single wall PVC vent pipe for exhaust discharge purposes in a closet, behind the solid doors, with no air supplying vents, or in any type of room that doesn’t conform to the combustion air requirements for fuel burning appliances.
Inadequate amount of air will cause incomplete combustion, and one of the bi-products of that is Carbon Monoxide, which could be deadly.
There are also single-concentric water heater power vent / PVC vent pipe systems used by a high efficiency and high efficiency condensing storage / tank type water heaters. They have combustion air supplied from the exterior (some water heater PVC vent pipe systems might be 2 pipes starting at the water heater and converted into one concentric pipe before wall / roof penetration).
Water heater power vent systems utilizing double PVC vent pipe also come in high efficiency and condensing high efficiency “flavors”.
PVC vent pipe water heater power vent system cannot be connected to the regular chimney or share venting with other appliance (e.g. water heater power vent and a high efficiency furnace cannot be venting through the single PVC pipe)
Typical water heater power vent equipped system utilizes (unless otherwise specified by the manufacturer and/or by your local jurisdiction) 2″, 3″ or 4″ diameter, schedule 40 PVC, CPVC or ABS pipe. Size of the vent pipe depends on model, BTU rating of your appliance, length of the entire horizontal and vertical pipe section, and the number of installed elbows.
Example (based on A.O. Smith Water Heater Power Vent requirements):
GPVH-40 and GPVH-50 model (40 and 50 gal / 40,000 and 50,000 BTU) water heaters.
Max water heater PVC vent pipe length would be:
40’ for 2” pipe
120’ for 3” pipe
160’ for 4” pipe
However, for every installed 2”&3” elbow you have to deduct 5’ from the maximum distance, and for a 4” elbow – 8’ of the pipe.
Always check water heater power vent system PVC vent pipe requirements that apply to your particular model. If you are missing the water heater PVC vent system installation manual, contact the appliance’s manufacturer / check online if possible.
Again check the manual, but some of the most common water heater power vent PVC pipe requirements are:
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This article was written by Dariusz Rudnicki
I'm a retired Illinois home inspector, founder and editor of checkthishouse.com, a blog which attracts around 2 thousand readers daily and is dedicated to answering the many questions of home owners and home buyers. Connect with me on Google+ Find me on Google+ Local