Do I really need to replace this flex duct...or can I just be cheap?


Old 07-14-13, 11:58 PM
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Join Date: Oct 2012
Location: USA
Posts: 10
Lightbulb Do I really need to replace this flex duct...or can I just be cheap?

Our water heater blew last July and flooded our downstairs. My wife and I were both at work when it happened so there was a nonstop flow of water into our house for probably a good 6 hours. After ruining our ugly "straight out of the 80s" parquet floor, our "used to be white" vinyl kitchen, and our lovely 6 month old chestnut hardwoods in the living/dining rooms; the water proceeded to find our air registers on the ground and dump down into the HVAC ducts in the crawlspace. The water accumulated in one 6" insulated flex duct and caused it to tear off of the register.

I got the house all dried out and the ducts cleaned, then went into the crawlspace and remembered that the duct was still down. I quickly realized that the insulation was still soaking wet and the duct needed replacing. Its other end was connected to the trunk line so I took it off the collar and planned to go to Lowes and replace it later that day. I didn't want my AC pumping into the crawlspace until then so I looked around and happened to find the circular piece of the trunk line that was cut out in order to install the collar connection onto the trunk. So, using all the ingenuity I could muster I crammed the cut out into the collar, thus solving everything.

To make a long story short, I didn't replace the duct that day and it's been about a year since this happened. The cut out is still in place and when I looked at it today, I could only feel a tiny bit of cold air getting past the cut out. I haven't noticed that my energy or gas bills have increased since then so I'm wondering if it's even worth replacing the duct.

I only need 8ft. of 6 inch insulated flex duct, but Lowes and Home Depot only sell 25ft. at a time and it's around $30 for just the duct. Then I have to buy mastic, HVAC tape, a worm clamp, supports, and zip ties. Only the worm clamp is cheap (about $2). And since you can't buy small quantities of anything else or the product is just expensive ($11 for HVAC tape), I would be spending about $70 to fix something that I'm not convinced is a problem, and I would have a whole lot of extra material that I really doubt I would use anytime soon.

Since the duct connected to a return in our hallway near the front door, I don't think I would notice its absence. And if I went into the crawlspace and really sealed up the collar (or removed it and sealed up the trunk), wouldn't it be like there was never a hole there? Wouldn't the AC/heater just blow the air that would have gone into that duct throughout the rest of the house?

Sorry this was long winded but if anyone has any thoughts on this I would love to hear them.

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Old 07-15-13, 01:01 AM
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,400
You can do whatever you like but I assure you that no duct was ever installed on a whim. You could be doing the equipment harm with either high pressure on the discharge or low air flow on the return, or both.
Old 07-15-13, 05:26 AM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,671
Why do you need tape? flex, hangers and tie straps
Old 07-15-13, 01:50 PM
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 10
I thought that after you put the flex on the collar you used the tape to seal/connect the flex to the trunk.

Even without the tape it's still about $60, and I still would rather not spend that if it's not necessary.
Old 07-15-13, 02:01 PM
Gunguy45's Avatar
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Join Date: Dec 2007
Location: USA
Posts: 21,045
You might want to check with a few HVAC contractors and see if they'd be willing to sell some leftover duct from a job. They probably throw away scraps like that every once in a while when they don't get used. Prob sell you that length for $5 or so. Heck...maybe a dumpster dive is in order? As to the foil tape (if you want to use it, apparently not really needed) I see it at Lowes and HD for $8. I always have a roll around and it rarely gets used for HVAC purposes.

So, looks like less than $20 most likely.

I'd fix it.

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