Gas Water Heater PVC Vent Pipe and WH Power Vent

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Gas water heater power vent and water heater PVC vent pipe

The following information does not apply to a tankless type water heater power vent systems.

Water Heater PVC Vent Pipe - induced draft ventingWater heater power vent PVC pipe - induced draft venting 2Water Heater PVC Vent Pipe - induced draft venting 3

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.

PVC vent pipe water heater power vent system (single wall PVC)

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).

PVC vent pipe water heater power vent system based on 2 pipes


This system is called direct vent, uses one PVC pipe to supply combustion air from the house exterior and second PVC vent pipe to discharge exhaust gases beyond the house. Both PVC vent pipes MUST terminate on the outside.
Advantage of the 2 PVC pipe water heater venting system (and a concentric / single pipe), is that you can install this type of the water heater power vented system in the closet / behind the solid door, or crawlspace with no vents, etc.

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)

Types and sizes of pipes that can be used in water heater power vent sytems

Water heater power vent PVC pipe - SCH 40 PVC, CPVC and ABS pipes are used for ventingTypical 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.
Water heater PVC vent pipe clearances at side wall penetrationWater heater power vent PVC pipe connections must be air tightWater heater PVC vent pipe roof clearancesAlways 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.

  • Gas water heater power vent / induced draft gas water heater PVC pipe can be installed vertically (through the roof) and horizontally (through the wall). For horizontal installations is should be supported every 3’ – 3 ½” to avoid sagging along the run (or per manufacturer’s instructions).
  • All connections on the gas water heater power vent system PVC vent pipe must be air tight (require primer and cement for PVC/CPVC/ABS pipe)
  • Slope of the pipe – always check manual, but for non-condensing installations (not high-efficiency water heater) level or slightly up-slope towards the exterior should be OK.

Gas water heater power vent / induced draft gas water heater PVC pipe exterior terminations

Again check the manual, but some of the most common water heater power vent PVC pipe requirements are:

  • Horizontal exhaust outlet 12” minimum above the ground or expected snow level (for cold climates)
  • Vent riser – 24”(if pipe penetrates the wall lower that 12” from the ground)
  • Minimum 18” above the highest point where it penetrates the roof
  • Minimum 6” away from the vertical wall
  • Exhaust pointing down with rodent screen at the end
  • min 36″ above the forced air inlet if closer than 120″ horizontally to the inlet
  • min 9″ -12″ from the window / door opening (depending on BTU rating)


Below are links to some of the manuals available online showing different types of water heater power vent installations.

Did gas water heater maintenance ever crossed your mind? It’s very important for your safety and to maximize your appliance’s performance.

Also, follow this link –  garage water heater installation if you’re planning it, or to check on an existing one.

Feel free to ask if you have any questions about the gas water heater power vent system and water heater PVC vent pipe.

Search existing Q&A in Gas Water Heater Answers

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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

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