Author Topic: Flue replacement & combustion air duct for water heater?  (Read 3404 times)

Ashyukun

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Flue replacement & combustion air duct for water heater?
« on: February 20, 2014, 02:10:59 PM »
My house is finally headed toward selling, and I've got a short list of repairs that the buyer wants done before the closing mid-March. Many are simple things that I know just how to handle, a few are certainly beyond my skills and I am arranging for pros to handle- but there are two that are things that are in a grey area where I'm not sure whether they're things I should just handle myself or get a pro to do.

First- the furnace flue in the lower of the two attics (house is a tri-level) "Furnace flue in the attic show signs of rusting
and deterioration at the lower attic. Small holes are developing."

The full report has a small picture that somewhat shows the flue in question- I've not had the chance to get over and look at it in person yet, but I'm wondering is this something someone who's reasonably handy should be able to handle themselves? Or is it something that I really need to have a pro do? (and if so, what kind of contractor? HVAC?)

Second- For the gas hot water heater: "Combustion venting appears to be inadequate. This can starve the unit of needed
oxygen and may allow spillage of flue gases into the living area. The addition of combustion air vents are needed to remedy this deficiency."

For reference, this hot water heater is installed in the small half-bath in the house's basement. The room is roughly 5' by 10'. The furnace is located elsewhere (in the crawlspace).

I did a bit of reading up on this, and as I'm understanding this just means that I need to have some kind of ducting to the outside (or into the crawlspace, according to my reator) that allows more air from outside of the house into it. I really think this is unnecessary as it's worked just fine for the 50 or so years that the house has been standing without it, but they have asked for it. Can I just install a vent through the drywall next to the HWH into the crawlspace and call it good?

Thanks!

Greg

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Re: Flue replacement & combustion air duct for water heater?
« Reply #1 on: February 20, 2014, 03:34:06 PM »
There are a few options.  You could install two louvered (for privacy) vents in the bathroom door, one high one low, so that the heater has the whole basement to draw from.  Some places don't allow this.

You could install a intake vent close to the bottom of the water heater.  If it's in a closet this would be ok, if it's just in the bathroom this could create a chilling draft.

If the heater draws from the bathroom, another option is a louvered door for the bathroom.  This would reduce sound privacy for the bathroom but it would certainly allow enough ventilation.

Another Reader

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Re: Flue replacement & combustion air duct for water heater?
« Reply #2 on: February 20, 2014, 04:21:20 PM »
You could have liability issues with a DIY involving combustion products.  I would call in a pro.  Plumber and/or HVAC.

Ashyukun

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Re: Flue replacement & combustion air duct for water heater?
« Reply #3 on: February 21, 2014, 06:46:30 AM »
I've got to have a plumber do some work on the water heater (pressure relief system) and they'll be looking at it this afternoon, but it sounds like from talking with them that they wouldn't be the ones making a call on the vent but will look at it anyway. It's a bit of a head-scratcher to me why it's an issue... I've read up a good bit on the combustion air ducts, and I can't see how one is really necessary in this situation. The room is definitely not a closet, and the house itself is roughly 50 years old and is nowhere near as air-sealed as more modern houses. I really have to wonder if the door to the bathroom had been left open when the inspector came through if he'd have still flagged it. :P

Exflyboy

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Re: Flue replacement & combustion air duct for water heater?
« Reply #4 on: February 21, 2014, 10:48:47 AM »
You can call your local building inspector and have them fax (or you can probably go in to the office) you the current code requirements for the vented water heater.. Simply have that on hand and point to where the existing vents are (if they exist) or add a vent pipe of louver as required.

You just need to be able to show the house inspector how the installation meets code.. In fact you only have to show that it met the code at the time it was installed, but finding out historically what that was can be tricky if it was more than a few years old. Its normally so many sq inches of opening required per 100,000 BTU's/Hr or in a room of "x" sqfeet.

This is all well within the scope of DIY to add an opening if required as Greg mentioned... no plumber or HVAC tech is required.

Frank

Ashyukun

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Re: Flue replacement & combustion air duct for water heater?
« Reply #5 on: February 21, 2014, 01:17:49 PM »
Well, the plumbers thought that the combustion venting shouldn't be an issue, but also said that and HVAC company would be the better authority. They also said that the relief valve gravity drain was not truly required given the install had been inspected and signed off when it was installed- but I may have no choice but to have it changed depending on what it seems like the buyer will sign off on. The good news is that the actual inspection agreement form didn't specify that anything had to be done and signed off by a code inspector or the likes, so if I put in an air vent to the nearby crawlspace it will likely pass their looking it over.

I got the chance to look up in the attic at the flue pipe, and I'm 99% certain that I can replace that myself- it's just a matter of taking out a few sheet metal screws holding the pipe section in place, taking it to Home Depot and getting a replacement, and then screwing that back into place. Easy as pie.

Exflyboy

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Re: Flue replacement & combustion air duct for water heater?
« Reply #6 on: February 21, 2014, 02:04:06 PM »
yup.. Class B flue vent if memory serves.

Frank

Ashyukun

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Re: Flue replacement & combustion air duct for water heater?
« Reply #7 on: February 24, 2014, 08:26:43 AM »
So I spent the better part of the weekend working on the inspection items around the house, including replacing the flue pipe. I lucked out and found that among some of the 'debris' that I needed to clear out from the crawlspace that had been left behind likely from when the furnace was replaced was ducting of the right size to replace the flue pipe. It generally went well other than a minor incident when putting the fixed pipe back into place that required climbing up onto the roof to reposition the rooftop 'stack' on top of the flue pipe.

Haven't done anything yet with the combustion duct, but I'm currently leaning toward putting a vent on the door into the bathroom- I noticed yesterday that there is a similar setup on the door to the furnace room in the Sunday School wing of our church. There will be the opportunity to put one in going through to the crawlspace since I'm going to have to cut out a portion of wall for the plumbing work that needs to be done, but I really worry that doing so will result in a lot of problems controlling the temperature in the basement since it would essentially be open to the crawlspace.

Overall though I was quite happy with the work I got done over the weekend- saved a LOT of money doing all this stuff myself and just have a few things left to be done as far as inspection items before the closing in two and a half weeks.

Exflyboy

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Re: Flue replacement & combustion air duct for water heater?
« Reply #8 on: February 24, 2014, 05:25:37 PM »
nice..well done..:)