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Water heater vent pipe sizing

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If replacing a 50 gallon+75 gallon water heater piped together-natural vent with one 75 gallon heater, any mismatch issues with current diameter vent?
asked in Gas Water Heater by gmanbox (120 points)
edited by darekrudy
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1 Answer

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smileyHi Gmanbox,
I really have no idea; you didn’t tell me a few important things:
  1. What is the current diameter of the chimney flue liner?
  2. What are the BTU’s of the old and your new water heaters (it should say on their labels)?
  3. What are the vent pipe diameters at the draft hoods / draft hood collar diameters?
  4. What else is currently venting into the same chimney? If there’s another appliance what are its BTU’s, vent pipe size, does it have an induced draft motor to push exhaust gases into the chimney? 
  5. Approximate vertical length of the chimney measured from the top of your water heater to the top of the termination point above the roof.
Please answer my questions so I can figure it out for you. Just click "comment" below.
answered by darekrudy (21,730 points)