Water Heater PVC Vent Pipe and Power Venting
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Water heater PVC pipe venting information below does not apply to tankless type water heaters.
PVC vent pipes can be used only with power-vent /exhaust motor equipped water heaters also known as an induced draft gas water heaters (also CPVC and ABS but some manufacturer and local restriction may apply to all 3 types).
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, always check your particular water heater model for the manufacturer requirements and contact local jurisdiction authority.
There are two types of PVC pipe water heater venting systems – single (single wall and concentric) and double pipe.
Water heater PVC pipe venting system (single wall PVC) discharges exhaust gases through that single pipe. However, it 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 that uses a single wall PVC vent pipe for venting in a closet, behind the solid doors / no air supplying vents or 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 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 PVC pipe venting system based on 2 pipes (direct vent) uses one PVC pipe to supply combustion air from the house exterior and second 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 concetric / single pipe), is that you can install this type of the water heater in the closet / behind the solid door, or crawlspace with no vents, etc.
Water heaters using double PVC vent pipe also come in high efficiency and condensing high efficiency flavors.
Water heater PVC vent pipe cannot be connected to the regular chimney or share venting with other appliance (e.g. power vent water heater and a high efficiency furnace cannot be venting through the single PVC pipe)
Types of pipes that can be used for power vent equipped water heater
Typical power-vent equipped water heater venting 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 Power-Vent Water Heater 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 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 manufacturer / check online.
- 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 instructions).
- All connections on the water heater 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.
Power-vent induced draft gas water heater PVC pipe exterior terminations – again check the manual, but some of the most common 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 installations.
- Power direct vent (water heater with 2 PVC vent pipes)
- PowerVent Induced Draft Gas Water Heater by RUUD / single vent pipe
- A.O. Smith single PVC pipe Power-Vent water heater
- SUPERFLUE - ultra-quiet power vent equipped water heater
Don’t be afraid to ask …
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