Venting issue with gas hot water tank

16 years ago

We recently gutted a few rooms for a major kitchen remodel, and in one of the walls we found the vent for our gas hot water tank. It takes up about a 3 foot by 2 foot space in the wall. We were thinking of switching to an electric hot water tank tank, removing the vent, then using the space for a built in pantry for our kitchen. (we could use the extra storage) Here is a view of the "ductwork" from the kitchen side:

Here is a view from the dining room side:

I am posting my question here because someone on another board recommended looking into different venting materials that may be possible here. Something less intrusive that could allow me to create the pantry AND keep the gas hot water heater.

I would also appreciate any other alternatives anyone may have. We are considering going from gas to electric with the hot water heater.

The vent goes up through two floors and creates another annoying bump-out in our upstairs hallway (which is already on the small side, so not having that vent would help)

Any thoughts?

Featured Answer

houndhandler

16 years ago

I did the math in my area and electricity @ .12 KWH is slightly more expensive than propane @ $3.50 per gallon, but if you use more than baseline electricity (which you would to heat water) electricity becomes more expensive.(.17 KWH)
Natural gas is unavailable to me, but if it was available @ the regional cost of about $1.30 per therm (roughly equivalent to a gallon of propane in BTU's) it is about 1/3 the cost of propane !
Math formulas available upon request.

BTW, the flue shown in the pictures appears to be in violation of code because it has too many 90 and 45 degree elbows.
A power vent or a direct vent would be an option, I like direct vent as it uses outside air for combustion.

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Comments (6)

Brewbeer
16 years ago
Some gas fired water heaters can be vented through a 3 or 4 inch PVC pipe, but it is unlikely that your existing gas fired water heater could be vented in this manner. If you want a gas water heater, you would prolly need to replace your existing with a higher efficiency unit.

If you did replace it with a higher efficiency unit that uses a power vent and PVC piping, you many be able to vent it through a sidewall in the basement.
jamesk
16 years ago
If you replaced your current atmospherically vented gas water heater (which I'm assuming is in your basement) with a direct-vent model or a power-vented model, you could eliminate the vent pipe snaking up through your walls altogether.

The vent pipe on a power-vented water heater would simply go out horizontally through the top of the basement wall. A power-vented water heater doesn't even have to be near an outside wall. You'd just run the vent pipe from the water heater to the outside wall.

Click on the link below then see page 6 in the pdf file that comes up. It will explain the different types of vent systems for gas water heaters.

With a power-vent water heater, you can simply remove all of the existing vent pipe that's in your way. Problem solved!

Here is a link that might be useful: Water Heater Information
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Both the 22v50 and the direct vent 22dv50 have the same energy factor of .58 with a estimated av energy cost of $235. The 22v50 is your basic 50 gal gas water heater. Unless you don't have combustion air available, there is no reason to go with the direct vent. The direct vent would also require redoing all of your venting since they get their combustion air through a coaxial vent. Their largest tankless unit with 35 degree inlet water would put out just about 4.7 gal a minute at 105 degrees. That is about 2 showers at the same time. There are other units out there that can heat more water You are right about the gas line-- it needs to be 3/4". More importantly from a reasonable installation cost standpoint is that you need to keep the flue short since it is a special stainless steel vent. If you can relocate the heater to an outside wall and then vent through the wall it works best. You cannot reuse your existing vent if you were to go with a tankless. Your plumber might have the best idea, just keep it simple and cheap. Insulate the tank with a $15 tank insulation kit and insulate the pipes then call it good. Put your money towards saving energy somewhere else.
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gardenwebber
Original Author
16 years ago
This probably isn't the area of expertise here on the plumbing forum, but I'll ask anyways:

Are gas hot water tanks that much more efficient than electric ones that investing in the power vent option would make more sense in the long run than simply switching from a gas hot water tank to a larger electric one?
Brewbeer
16 years ago
When you say "efficient" do you mean "cost effective"?

The answer depends on what you are paying for gas vs. what you are paying for electricity.

Also note that you can't compare a 40 gallon gas water heater to a 40 gallon electric model, because they don't have the same capacity to make hot water. You need to look at the first hour rating and the recovery time of each. To get a similar supply out of an electric water heater that you are now getting with the gas water heater, you will likely need a water heater that is 50% to 100% larger than the water heater that you have now.
jakethewonderdog
16 years ago
Okay, Let me first say that I don't think the vent, as its currently constructed, meets code. Just a wild guess...

Second, as BrewBeer pointed out, you really need to compare the price of gas to electricity. In many locations, gas costs about half the price of electricity.

I would second the powervent or direct vent idea. However, for similar money, you could also potentially get a tankless. If you can install the heater with a short vent, a tankless would cost about $1000-1200 in materials. You would need to size it properly and determine if your gas supply is sufficient. A power vent water heater is about $1200 also.

A gas tankless is about 35% less to operate than a standard gas tank heater. (Energy Factor of .60 compared to .83)

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