best method of sealing metal ducts

[Bob Slater]

Just got all the ductwork overhead last night. I haven't bolted anything down yet, and was wondering if there is any kind of paint on sealant for the joints. It seems to me this would be neater than slobbering caulking or silicone on it. I might also use aluminum tape if that is preferable. I think I will be painting the ductwork to blend in with the ceiling if that makes a difference. I have new respect for duct specialists, as that was one time consuming job that would have been easy to knick a finger doing. One piece of ducting fell off my bench and cut right through my jigsaw's power cable.

[Prashun Patel]

Have you google'd 'duct mastic'?

[Ted Calver]

Bob,
I used the aluminum tape where I could and silicone where the tape wasn't practical. I did not paint though, and don't know how well paint would stick.

[Rod Sheridan]

Duct sealing compounds that are applied by brush are perfect, since they're designed for sealing seams on ductwork....Rod.

[Dan Keeling]

+1 for using mastic to seal ducts
I don't know how paintable it would be, but there are certain brands that are white instead of the usual gray. Masking tape about an inch or so on either side of a joint to leave clean edges.

[Bob Slater]

Thanks for the tips. Rod, have you seen the duct paint locally? At Home Despot I am hoping.

[Michael Peet]

I just did a bunch of metal ducting in my basement not too long ago. A bead of silicone caulk and then a wrap of aluminum tape at each joint is what I did. Some people screw theirs together so they can take em apart easier.

[Jim McFarland]

Thanks for the tips. Rod, have you seen the duct paint locally? At Home Despot I am hoping.

Bob, not sure if same thing Rod uses but I found this (DP 1030 water based duct sealant) at the local Lowe's and seems to seal the dust collector ducts just fine:
http://www.pacificduct.com/vendorSub...oly/dp1030.pdf

[Lewis Cobb]

I have painted galvanized duct successfully - here's the "trick" that an expert put me on to -

1) degrease it first - and do it several times - I used MSP and a sponge for the outside, then used a mop swabbing the inside (just to be sure there was nothing inside that would possibly leach out around the ends or wick through the seam (I was doing spiral pipe)

2) After degreasing - I flooded the surface with water and wiped it down until dry. The surface was very shiny but "squeaky" clean.

3) "UMA" made by a company X.I.M - it's a water based primer that will go on and stay on the galvanized surface.

4) Top coat with what you want - I used an acrylic semi-gloss paint

Cheers,
Lewis

[Bob Slater]

Jim and Lewis, and Michael, great tips. There are no Lowe's nearby, so hopefully HD has the same stuff.

[Sonny Edmonds]

I used S&D drain pipe and fittings.
So it was sealed without adding anything. But I did use 2" pipe wrap tape to make sure it didn't move.
My buddy who did our HVAC replacement used this mastic stuff that sealed up any seams in the metal parts. Good stuff, Maynard!
Keeps the ducts sealed for a wide range of heating and cooling.
Tapes will eventually come loose.

[Jim Becker]

Heavy aluminum HVAC tape for straight seam sealing and HVAC mastic for adjustable elbows, etc. You can use silicone caulk in lieu of the HVAC mastic with similar results.

[Chip Lindley]

My *double-edged GLOAT* on duct pipe. When I bought my used Oneida 3hp for $1100, it included a whole shop-full of galvenized thin-wall ducting. All the joints had been sealed with great gobs of BROWN silicone! The nastiest looking mess I ever saw. Clear would not have been nearly so bad. I will now use a side grinder with wire brush to get off all the BROWN before I configure my own DC ducting! Oh Well, ya can't have it ALL!

[Bob Slater]

My *double-edged GLOAT* on duct pipe. When I bought my used Oneida 3hp for $1100, it included a whole shop-full of galvenized thin-wall ducting. All the joints had been sealed with great gobs of BROWN silicone! The nastiest looking mess I ever saw. Clear would not have been nearly so bad. I will now use a side grinder with wire brush to get off all the BROWN before I configure my own DC ducting! Oh Well, ya can't have it ALL!

Good deal, because when I added it all up , the darn ductwork and gates cost about as much as the DC. If I did it again, I would probably use plastic. For some reason, the place I bought it off of sold me about $100 more pipe than my design called for on paper.

[Joe Chritz]

I doubt plastic is really that much more affordable since everything (especially the fittings) adds up very quickly.

Since it is almost inevitable that you will change the layout in the future I would just go with silicone (paintable if you will paint) and foil tape. Silicone on the inside is really really hard to get apart when you need to.

This is one of those "DOH!" moments I am so fond of having.

Joe