Why do gas water heaters require external venting while gas stoves do
not? Is there something fundamentally different in the combustions
byproducts (CO vs. CO2) that need to be vented for the water heater
and not the stove?
If the only reason is the volume (BTU rating) of byproducts, it
doesn't make sense. For example, a moderate water heater can have a
rating of 75,000 BTU, while a high end stove will have a total BTU
rating over 100,000.
Worse case, think about cooking a Thanksgiving meal, oven is on for
six hours and all the burners are going, all this is vented inside the
house. While downstairs the water heater just has a pilot light
going. Why is one required to have external venting while the other
In Minnesota at least, a gas cook stove does indeed require ,by code,
a vent which goes outside. I'm sure that's true of many other states
as well. I have seen unvented stoves but they have never been seen by
a building inspector, I bet.
Regardless of code, it is recommended and worthwhile to have a hood
for your gas range. I don't always use mine but that is what is
recommended by the safety pundits.
Minnesota is a very nice place to live and I don't ever want to
leave. I will agree that the State can be a bit paternal at time, as
We have long winters here where folk heat their homes continuously for
many months of the year. Every year ordinary people are killed here
by carbon monoxide poisoning. Its stuff like that that causes the
legistature to pass such laws. Grieving relatives are very hard to
say no to in a State like MN where even small things can make very big
I doubt if you can disagree that a hood is a good idea for any cook
stove. Your state may be less restrictive than MN but that won't
cause me to move there no matter where it is.
Our stove has four 15,000 BTU burners. This is on the high side for
residential cooktops. When I have all four burners running on max
(60,000 BTU) for any length of time (a minute or two is all it
takes), the kitchen gets hot enough that I have no choice but to open
virtually all of the windows on the first floor, particularly with a
houseful of guests, as likely would be the case with a big
Thanksgiving dinner. I can't imagine how uncomfortable 100,000 BTU
would be in that situation. The open windows are plenty of
I think the difference is in the fact that the kitchen range generally
operates while being observed and the water heater operates day and night
where no one can observe whether the flame is burning at all, whether it is
burning yellow and creating lots of carbon monoxide, or burning too high
because of a regulator malfunction.
No one recommends leaving the kitchen range burning unattended all night
while the house occupants are asleep, which is what the water heater does.
People have been killed by improperly vented water heaters and by using gas
ranges for heating the house but they are both very safe when properly
installed and used.
Good answer! Logical and concise.
I live in an 8500 DD climate and hate to see my heating $ go to
waste. So now I think I'll move the water heater to the kitchen/LR
where I can keep an eye on it, and install a timer so it doesn't run
at night :).
Actually I plan on looking into retrofitting a vent damper to isolate
the water heater from the vent stack when it's just on pilot.
Actually a 4 burner plus over gas range creates very little CO when
it's burning correctly. Also, as another poster mentioned, the stove
can be observed wihile a semi hidden gas water heater can not.
I've run my unvented gas oven consistently and have a CO detector in
the kitchen. My detector is one of those Nighhawk types that with a
push button, can give low level reading below the alarm threshold.
Rarely do I see even any trace CO from the range.
Occasionally during summer days, I've seen trace amounts of CO on the
detector that come from outside air. The ambient air due to distant
auto exhaust probably has more CO than a properly operating gas range.
I've never thought that range hood venting was even designed for CO
elimination. They are more often designed for odor and smoke
elimination. Many such range hoods are not even vented to the outside.
They are vented within the home after having the gases pass thru
BTW, the standard gas water heater has a burner BTU rating of 35,000
BTU/hr, that's nowhere near 75K/hr. The only gas water heaters that
I've seen with 75K or higher rated burners were commercial units used
in apartment buildings.
A good range hood vented to the outside WORLD to remove that oven heat is
lots more efficient than your AC !!
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