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can a direct vent water heater be replaced with a standard/natural vent WH?

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I have a old apollo hydroheat system where the water heater/boiler is located on the middle floor of a townhome next to an exterior wall (the closet is small and located in the kitchen area). the water heater was a direct vent model and vented thru the side wall a few inches above the WH. Can i replace the water heater with standard vent model (same as natural vent I assume)? I wanted to keep the direct vent model (State Select) but apollo is out of business and the new State model is taller. In the blog it seemed that you stated that a natural vent cannot go thru the side wall. Note we live in Illinois. I keep getting conflicting information so any guidelines would be helpful.

Thanks. Dave
asked in Plumbing by schorschman (120 points)
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1 Answer

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Hi Dave,
It seems to be an extremely popular concern and I did answer it a few times already smiley.
You cannot vent a natural draft water heater through a side wall.  One of the answers is at the following link - http://checkthishouse.com/qa/343/natural-draft-gas-water-heater-sidewall-venting
Let me know if you have additional questiones. Just click "comment" below
answered by darekrudy (21,730 points)

Thank you for your answer. 

You mentioned a water heater with draft hood is required to be vented in to a chimney. Can you point me to the required code section so that I can show to the contractor?  

I am being asked to use a State Select SL model GS650YRRTL (standard/natural vent which I believe is covered by your remarks) to replace an old Apollo A6 50 XBDS L (a direct vent model). It has been a nightmare finding a non-powered direct vent tank that is no larger (height, 61", so that old vent can be used; diameter is secondary but most seem to have 0" tolerance/clearance of side walls) than the Apollo tanks no longer being made. I am considering the State Select SL power vent models (GS6 50 YBPDT L) as they are the same height as the old Apollo but am worried about the fan noise as the WH is located on the second floor of the townhouse in a small closet off the kitchen/washer-dryer area.

thank you,


p.s. sorry if duplicated follow-up; also tried email reply.



Hi Dave,
Show the code section to your contractor? smiley
If he doesn’t know how to properly vent a natural draft water heater I wouldn’t hire him at all. Any appliance should be installed by following its manufacturer’s instructions and local codes. So if the water heater is Listed (approved) for the side-wall venting by the manufacturer, there are no local laws and building design obstacles preventing it, you can have it installed that way.
If the water heater is not Listed for side wall venting it should be installed as such because it’s hazardous. 
Venting requirements are based on the appliance’s category (there are 4 categories) and most of the natural draft type water heaters (including State Select SL model GS650YRRTL) are classified as Category I appliances where the exhaust gasses entering the flue are gravity-vented under non-positive pressure. 
Just like other 3 categories venting system of Category I appliance must follow certain rules so the exhaust gasses have proper environment to pick-up speed and discharge outside of the home. They simply require a chimney because horizontal venting will not provide that environment. 
"A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer’s installation instructions, and shall be constructed and installed to develop a positive flow to convey combustion products to the outside atmosphere."
There are 5 types of vents permitted to be used with Listed (UL) Category I / Listed appliances with draft hoods / appliances listed for B vent:
Based on IRC (International Residential Code) UMC (Uniform Mechanical Code)
  1. Type B gas vent – 2427.6 (IRC) and 802.6 (UMC)
  2. Chimney – 2427.5 (IRC) and 802.5 (UMC)
  3. Single-wall metal pipe - 2427.7 (IRC) and 802.7 (UMC)
  4. Listed chimney lining for gas - 2427.5.2 (IRC) and 802.5.1.3 (UMC)
  5. Special vent listed for appliance - 2427.4.2 (IRC) and 802.4.3 (UMC)
Type B vent MUST terminate minimum 5 feet above the draft hood so technically you could go through the wall and up / above the roof (if such installation is permitted in your area… since this is a townhome / association may not approve it) 
"Vents for natural draft appliances shall terminate at least 5 feet (1524 mm) above the highest connected appliance outlet, and natural draft gas vents serving wall furnaces shall terminate at an elevation at least 12 feet (3658 mm) above the bottom of the furnace." 
As for the noise, this water heater is considered as the most quiet one, but I’m not sure about the dimensions - http://www.gtaaire.com/pdf/GSW_SuperFlue_Wholesale_FINAL_PG202C_Oct0605.pdf
I hope this helps a little...