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In-Slab Duct Damage
We noticed that our laundry room and downstairs powder room were cold this winter, and when the heat was on, minimal airflow was coming from the vents. I used my borescope to check out and it looked like there was damage, so we called in our local HVAC company with a better quality camera, and sure enough, right where the bathroom line tees off, it's rusted out completely.
In my crude diagram below, the break is at "3". The area between the heater and the tee (around "1") is the family room, with in-floor vents that work just fine.
This is under the slab, and I'm trying to weigh my options:
1. Cut into the slab and repair the tee at '3'.
2. Re-line the duct "non-invasively" (is this even a thing?)
This is the only part of the duct that is damaged, and presumably the only part that would need replacement. Also, in the summer, there is a damper that is closed to minimize the A/C into those areas (they don't get uncomfortable).
Re-routing into the attic isn't an option given the "geography" of where the ducting is located - it would require running up a narrow external wall that has a window taking up approx 90% of the width of the wall.
Thanks in advance.
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Your attachment isn't there.
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Post Likes - 1 Likes, 0 Dislikes
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That's weird, it shows up for me. I'll add it here...
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If the rest of the duct work is good personality I'd saw cut at #3
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Basically an access hole, replace the tee and fill in?
Is this a days work, two days, etc? Just trying to figure out time off...
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I expect the rusting of the rest of the duct isn’t far behind. I suggest you consider alternatives, such as ductless.
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Some plumbing companies offer pipe liners installed with no excavation. Not sure if this would work in your situation, but may be worth exploring.
“A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.”
― Robert A. Heinlein
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Is your drawing to any kind of scale or just a pencil drawing for a general idea. I ask because by the drawing it appears the duct after the branch is bigger than what is coming from the heater. Generally it is bigger off the heater and reduces from there. Has the rust created a flap that is clocking the air flow then.
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How far from the tee to the bathroom outlet?
What you could try in the short term is to use a big shop vac to suck the fallen-in dirt out of the failed-tee area to allow air flow.
The in-floor duct systems were fine (although they are not heat-conserving-efficient as the direct-earth-couple creates an infinite heatsink) IF they were solid plastic ducts or if the metal ducts were elevated above the soil so concrete could flow all the way around them.
Most that I have seen were neither and so end up eventually failing as yours have. Along the same lines of logic as "you don't put one new tire on your car" - the single fail-point you have is likely to be just the first manifesting of the problem.
I don't like mini-split systems as a general go-to - so if this was my house I would be looking ahead to install a high velocity ducted system. The 2" air ducts are easily to route, the quality of the equipment is high, and their performance is excellent. They also provide far better air cleaning and conditioning options. Plus; they are not some ugly grafted-on looking BS on the walls or ceilings. <g>
BTW: What is your heating fuel?
PHM
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Originally Posted by
dmolavi
That's weird, it shows up for me. I'll add it here...
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
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Post Likes - 1 Likes, 0 Dislikes
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Does that system have a name?
Is it a solid line which gets pulled into the existing soil line?
Is it some kind of coating which gets applied and then hardens to form a pipe liner?
How does it work?
PHM
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Originally Posted by
Juan Madera
Some plumbing companies offer pipe liners installed with no excavation . . . .
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
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Post Likes - 1 Likes, 0 Dislikes
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Liner is put (blown) in as an epoxy saturated fabric tube, inflated and heated to cure the epoxy. Pretty slick operation.
“A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.”
― Robert A. Heinlein
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Post Likes - 1 Likes, 0 Dislikes
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Originally Posted by
Juan Madera
Some plumbing companies offer pipe liners installed with no excavation. Not sure if this would work in your situation, but may be worth exploring.
Yeah, I'm hoping this is an option. Cutting into a slab is...meh..in my mind. The engineer in me says a monolithic slab needs to stay that way.
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Originally Posted by
BNME8EZ
Is your drawing to any kind of scale or just a pencil drawing for a general idea. I ask because by the drawing it appears the duct after the branch is bigger than what is coming from the heater. Generally it is bigger off the heater and reduces from there. Has the rust created a flap that is clocking the air flow then.
Very much not to scale. Done in paint as a quick 'n' dirty. The line coming from the heater is 12 inches, and I'm guessing drops to the 6-8 inch mark by the time it tees off. I do have a picture from the camera that was run. I'll post shortly.
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Originally Posted by
Poodle Head Mikey
How far from the tee to the bathroom outlet?
What you could try in the short term is to use a big shop vac to suck the fallen-in dirt out of the failed-tee area to allow air flow.
The in-floor duct systems were fine (although they are not heat-conserving-efficient as the direct-earth-couple creates an infinite heatsink) IF they were solid plastic ducts or if the metal ducts were elevated above the soil so concrete could flow all the way around them.
Most that I have seen were neither and so end up eventually failing as yours have. Along the same lines of logic as "you don't put one new tire on your car" - the single fail-point you have is likely to be just the first manifesting of the problem.
I don't like mini-split systems as a general go-to - so if this was my house I would be looking ahead to install a high velocity ducted system. The 2" air ducts are easily to route, the quality of the equipment is high, and their performance is excellent. They also provide far better air cleaning and conditioning options. Plus; they are not some ugly grafted-on looking BS on the walls or ceilings. <g>
BTW: What is your heating fuel?
PHM
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My heat is forced air natural gas. Can these "high velocity" systems be installed in tandem with what's there? The furnace,etc are not old and do not need replacing.
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Here are some pictures from the scope. Pardon the scrawl - it was my wife's attempt to annotate the image on her phone prior to emailing it.
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The one in me says: edge-pinning and concrete glue works wonders. <g>
Originally Posted by
dmolavi
Yeah, I'm hoping this is an option. Cutting into a slab is...meh..in my mind. The engineer in me says a monolithic slab needs to stay that way.
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.