Is it permitted to run a horizontal water heater vent pipe along the ceiling rafters in the basement?

Home Maintenance Questions and AnswersCategory: Water Heater VentingIs it permitted to run a horizontal water heater vent pipe along the ceiling rafters in the basement?
Question by PhilD

I have a gas water heater located in a corner of my basement in Georgia. The vent goes out the top of the WH into a short S bend (8″)and then up through the first and second floors and out the roof. The WH is badly located for room renovations and I would like to move it about 15 feet into another section/corner of the basement. Utilizing the same vent is it permitted to run a horizontal(slightly elevated along the distance) vent tube along the ceiling rafters in the basement over to the existing vent port?


1 Answers
Dariusz Rudnicki Staff answered 1 year ago

Hi Phil,
There are two types of vent pipes used for natural draft water heaters – single and double wall. Both of them require 1/4″ per foot pitch between the WH and a chimney flue connection (always going up towards the chimney).

  • For the single wall pipe you need at lest 6″ clearance from framing and other combustibles, and max horizontal run must be smaller or equal to 75% of total vertical height. All joints fastened with screws and properly supported.
  • Double wall pipe (B-vent) requires 1″ clearance, and you can run it horizontally up to 100% of your vertical pipe – don’t use screws on this one except for the draft hood connection (it has special locks at each end) – if it is concealed inside the wall / ceiling – you have to use double wall type vent.

Keep the number of offsets and bends (S-bend?) to minimum because each one lowers capacity of your chimney. Other option is going through the side wall with an induced draft / PVC vent water heater.

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