I need a little "Water Heater 101" here.
We may need to replace our gas water heater soon. We have an unusual setup,
due to the people who owned the house before us. It's a normal gas fired
water heater, but it vents out through the nearby foundation wall. There is
an external blower on the outside of the house that turns on with the water
heater to suck the exhaust gas out. Odd arrangement, and sometimes the
heater goes out and I need to relight the pilot.
Anyway, we may replace it soon with either a power vented unit or a direct
vented unit. From reading manufacturer's web sites, I know *how* they
difffer. I just don't know the pros and cons of each choice. What's
considered "better"? And why?
Thanks in advance!
If you have a power vent on your exhaust now, you will probably
continue to need it. The only time that a power vent is used is
when it is impossible (or at least extremely difficult or expensive)
to direct vent. A direct vent must be almost vertical all the way
to the roof. Can you do that from your current water heater?
As far as pros and cons go, direct vent is preferable due to the
fact that there are no moving parts to break down or fail. If
everything stays in place, then the vent will function. When it is
not possible to do this, or if this would put a vent pipe through
the center of your bedroom (as an example) then you would go with
the power vent.
A power vent unit has a 110v fan on it that has to prove operation before
the gas burner will fire. A direct vent unit (DV) requires no electricity.
It sounds like the OP had neither, just a cobbled together POS.
Terminology gets a little confusing. Direct vent water heaters are
capable of horizontal venting within a limited range. Power vent
units can horizontally vent to a greater distancee, usually through
properly rated PVC. Atmospheric or conventional venting is what we
are all familiar with and requires a vertical stack to function
A power vented heater has a blower attached to it, simular to what you have
now, but all built into one unit.
A direct vent heater is very simular to a standard natural draft heater, it
differs in that it has "closed" combustion. It draws the combustion air from
outside and vents the burnt gases to the outside through a double wall vent.
No power vent needed, it works on convection. No electricity needed either!
I would go with the direct vent, less to go wrong. I believe a direct vent
needs to be set right at the outside wall, the vent is very short. A power
vent can run many feet, so this may make a differance in your case.
Thanks for the replies!
The distance from the center of the water heater to the inside of the
foundation wall is only 33 inches, so direct vent would be a good choice?
The direct vent draws in the outside air for combustion, right? (well, at
least the Bradford White model that I looked at does)
I will definitely call a licensed plumber to do the work, but I just like to
understand the issues.
Again, thanks for your help!
My direct vent doesn't draw outside air. The other thing to consider is,
direct vents are pretty loud from outside the house. Don't put it anywhere
near your deck, for instance, unless you want to listen to it every time it
Mark, it sounds like you WH is actually a power vented unit.
It can be a little confusing, but a power vent and a direct vent both go out
the side of the house. The main difference is the power vent uses a PVC
vent and has a fan on top to force the flue gases out. A direct vent has a
pipe inside a pipe and has sealed combustion.
Yep, you're correct. I was thinking "power vent" not "direct vent"
My furnace has a power vent, the wall mounted propane heater in my shop is
direct vent -- there's no fan on that one, and it does pull air from
outside. Sorry about that.
I just had a direct-vent installed; a GSW, identical (I think) to a
John Wood. Bradford-white makes 'em too. Go to their websites and
My direct-vent has a flexible coaxial stainless(?) steel pipe, outside
diameter 6" or 7", that goes out through the house wall just above the
sill, between the floor joists, so it definitely exits horizontally.
In fact, from the top of the unit, it bends a bit west, runs
diagonally a bit, then bends south to get to the wall. Total run is
maybe 5'. (The manufacturers have strict rules about this; it's on
their websites.) The exhaust is darned hot, far hotter than from my
power-vented sealed-combustion boiler. If I had light-coloured vinyl
siding I'd expect some discolouration above the vent, but I have dark
aluminum siding so I'm not too worried.
Although it draws outside air for combustion, the combustion chamber
is not sealed. It is accessible to light the pilot, and it is still a
I *believe*, in contrast, that power-vent units may have fully-sealed
chambers, slightly higher nominal efficiencies, and way less strict
venting options. Of course they require power.
I went direct-vent because I didn't want to depend on electrical
power, and I (really) didn't want to put in a flue liner (I replaced
an old electric unit).
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