Duct work question

[MartyMcFly3]

The way my home is set up, I have a 3" duct from the water heater meeting up with a 4" duct from the heater which goes through a 6" duct leading up the chimney. The way it was originally connected made it look like all three met in a "tank". Well the tank fell apart on me while installing a new water heater.

I tried going to home depot and the best I could come up with was a 6"x6"x6" wye fitting and would be using reducers. The problem with using these reducers is it makes the duct go past the water heater. Due to this, I pieced together the best I could using the old tank and taped it up there. No leaks but I can't imagine it being a permanent solution. Any ideas how to replace/fix this? I called one HVAC guy for an estimate and was quoted at $300 which seemed high. Any input is greatly appreciated.

I have included some pictures and can take more if needed. Thanks!

 

[drnickriviera]

Is that all single wall hvac ductwork used to vent a gas appliance?

 

[MartyMcFly3]

Yes. I am in Illinois if that means anything. I believe in some states that violates code, but this was how my house essentially was before I installed the new water heater and before I moved in (meaning paased code, at least at the time)

 

[MartyMcFly3]

I found a special order part at Menards. Think that'll do the trick.

 

[Red Squirrel]

What is the other duct for, is that the furnace? Single duct furnaces are really inefficient as they create a draft and suck cold air into the house. Well hot water heaters too, but furnace runs way more so it's more significant. I would consider budgeting to replace it with a high efficiency at some point, worthwhile in the long run, they have two ABS pipes for exhaust, one for intake one for exhaust. For now I'd say what you have is "ok". It is against code in most places, as it could cause gas from one appliance to spill out the other. But if it's code where you are then it works but do make sure you have a CO detector in that room.

I would maybe change it so the two small ducts only meet up at the very end, vertically, less chance of spillage that way since heat rises. you could probably fabricate a can for them to connect to, and seal it very good with some kind of high temp sealant. Foil tape might work too but I'd keep an eye to make sure it does not peal off. There is a gray stuff that is painted on that I've seen used to seal ducts too, but sure what it's called. That could maybe work better.

You can probably fabricate a "can" of sorts to have the two ducts meet up to then use aluminium tape to seal it. Make sure you have a CO detector in that room.

 

[MartyMcFly3]

Found a wye fitting that'll work. Will definitely keep your suggestions in mind, Red Squirrel. Thanks!

 

[slashbinslashbash]

Yeah I've never seen two appliances sharing the same exhaust vent. Probably it's not code compliant at this point, at least here in Texas. Whenever you re-roof the house, get the roofers to put an extra vent in the roof, and run a separate duct for each.

 

[NetWareHead]

Its code where I live to allow appliances to share the same exhaust vent/duct/flue, they just have to be the same fuel burning appliances. E.g. you cant share a flue with an oil boiler and natural gas water heater or vent either of those into a flue servicing a wood burning fireplace for instance. In our house we have 2 boilers and 2 water heaters (all natural gas) and all use the same masonry chimney.

Its also impractical and not cost effective to give a separate and dedicated flue to each and every appliance

 

[slashbinslashbash]

Its also impractical and not cost effective to give a separate and dedicated flue to each and every appliance

It's what all the houses do here... even though they're all natural gas (furnace and hot water heater) and often the appliances sit right next to each other. Literally you can drive around and see the roof vents within a couple of feet of each other. Must be SOME reason for it. *shrug*

 

[NetWareHead]

It's what all the houses do here... even though they're all natural gas (furnace and hot water heater) and often the appliances sit right next to each other. Literally you can drive around and see the roof vents within a couple of feet of each other. Must be SOME reason for it. *shrug*

If you are talking about those high efficiency units that use PVC pipe to exhaust, that's a notable exception. The last time I shopped for a boiler, you could not share those exhausts with other units. Plus, you can hide PVC in any wall and the route can take bends or horizontal runs unlike a traditional masonry chimney or stainless flue types which needs a direct rise to the roof

 

[Humpy]

It's what all the houses do here... even though they're all natural gas (furnace and hot water heater) and often the appliances sit right next to each other. Literally you can drive around and see the roof vents within a couple of feet of each other. Must be SOME reason for it. *shrug*

Poor design, laziness, low cost, and lack of skill is mostly the reason.

Just run everything straight up poking as many holes in the roof as you want and assume the roofers will make it work.

 

[NetWareHead]

Poor design, laziness, low cost, and lack of skill is mostly the reason.

Just run everything straight up poking as many holes in the roof as you want and assume the roofers will make it work.

 

[natto fire]

Poor design, laziness, low cost, and lack of skill is mostly the reason.

Just run everything straight up poking as many holes in the roof as you want and assume the roofers will make it work.

Not sure where that poster is located, or if they can tell the difference between roof vents. Around here, we usually use masonry chimneys for flues that have natural gas furnace and water heater vents together. These are on older houses. All the newer stuff around here uses high efficiency gas combustion and vents out the side with PVC, or mainly uses electric.

We still have normal vents for plumbing stacks and fart fans. Perhaps the vents next to each other they are seeing are just plumbing, HVAC vents and not the bigger flue vents.

 

[slashbinslashbash]

Not sure where that poster is located, or if they can tell the difference between roof vents. Around here, we usually use masonry chimneys for flues that have natural gas furnace and water heater vents together. These are on older houses. All the newer stuff around here uses high efficiency gas combustion and vents out the side with PVC, or mainly uses electric.

We still have normal vents for plumbing stacks and fart fans. Perhaps the vents next to each other they are seeing are just plumbing, HVAC vents and not the bigger flue vents.

Nope, I used to be a roofer, I know the difference between a pipe jack and a combustion vent. But again my experience is limited to Texas, where pretty much everything is natural gas. I took all of these photos myself. I probably have 30 more examples that I could show you as well.

http://imgur.com/a/l4vgL

These are all from the Houston area. In each of them you can see 2 combustion vents in relatively close proximity, with 2 appliances almost certainly sharing the same attic or closet space.

The first 2 pics are actually of the same house and taken back-to-back, so those 4 vents are within about 10-15 feet of each other. It was a 2 story house and probably had 2 hot water heaters and 2 furnaces. 3rd pic, they're not super close but the appliances are probably within about 10 feet of each other in the attic -- certainly close enough to have the vents mated if they had wanted to. 4th pic, about 5 feet from vent to vent.