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Installing a power vent hot water heater exhaust pipe

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We are installing a power vent hot water heater (a richmond model#6GR50PVE2-42). We need to install one PVC exhaust going out the side of the house. We have a high efficiency furnace already venting through the wall - two PVC pipes with the exhaust approximately 12" above the intake.

It would be most convenient to run the water heater PVC alongside the furnace PVC in our basement. If we did this, the PVC for the water heater would exit the house right next to the intake for the furnace.

According to the Richmond instruction manual, the water heater exhaust has to be 3 feet above any forced air inlet.

Outside the house, would it be acceptable to:

> Install a 90 degree fitting on the water heater PVC

> Extend the water heater PVC to 3 feet above the furnace intake

> Install another 90 degree fitting at the 3 feet higher level and then immediately after it install the 45 that came with the water heater

This would be done with the understanding that the total number of 90's/45's would not reduce the acceptable vent distance beyond the standards stated in the installation manual.

I contacted the Richmond/Rheem helpline and the person I spoke stated this would be fine but I don't think they knew what I was talking about.
asked in Gas Water Heater by pherman (120 points)
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1 Answer

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Hi Pherman,
I couldn’t find installation manual for your Richmond water heater model but since it’s made by Rheem the information at this link - http://www.rheem.com/documents/power-vent-with-electronic-control-power-vent-use-and-care-manual will probably apply to it as well. 
It appears that Rheem doesn’t put any length limitation on the exterior vertical section of the water heater’s PVC vent pipe and your assembly should work fine.
But, there are a couple of things that might need attention and their importance would partially depend on your geographical location / climate zone.
Power vent equipped water heaters are not condensing type appliances / condensate formation does not occur during exhaust process. However, there are some conditions including ambient temperature, humidity, vent pipe length, and PVC vent pipe slope that might result in condensation formation inside the vent pipe. 
To prevent any possible condensation from flowing back into the power vent’s compartment the horizontal vent pipe section should be sloped down towards the exterior 1/8” – ¼” per foot (so it drains outside) or up if the appliance has been equipped with optional condensate kit.  
With that exterior vertical section installed (and especially in cold climates) the PVC vent pipe horizontal part must be sloped towards the power vent assembly and condensate drainage provided. 
There are also items #7&8 on page 14 of the Rheem's manual that are important for cold climates and additional support requirement for vertical sections longer than 24” (applies to above the roof installations but vertical is vertical – page 15, item #3)
I would also verify vent pipe clearances recommended by the high efficiency furnace manufacturer.
Just click “comment” below if you have additional questions.
answered by darekrudy (21,730 points)