Model # WBA50

Internet #100396973

Store SKU #559722

Store SO SKU #1000683931

null Water Based Mastic Half Gallon Tub

Water Based Mastic Half Gallon Tub

  • Creates air-tight seals on duct seams and joints
  • Meets or exceeds most energy codes
  • Fiber reinforced, water based, low odor
$1195 /each
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Product Overview

Master Flow Water Based Air Duct Sealant helps seal all types of air ducts to reduce the risk of conditioned air leakage. Sealing air duct plenums, takeoffs, elbows, and vent boots where they connect and sealing the seams, per product instructions, may help save energy. The sealant is fiber reinforced and easy to apply by brush, gloved hand, or putty knife to flex duct, duct board, and sheet metal air ducts. It dries to a tough, flexible, and weather resistant seal. It adheres to many surfaces like: drywall, foam and fiberglass insulation, galvanized steel, aluminum, masonry, and wood. This product is also available in 10.5 oz caulk tubes.

  • Fiber-Reinforced
  • Weather Resistant
  • Non-Flammable
  • Low Odor
  • Earns LEED Credits
  • UL Listed

Info & Guides

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Product Depth (in.)
Product Height (in.)
Product Size (oz.)
Product Width (in.)


Full cure (hours)
Minimum Temperature (F)
Product Weight (lb.)

Warranty / Certifications

Manufacturer Warranty
Free from Manufacturer Defect at Time of Delivery.

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Customer Questions & Answers

after it dries how can I remove any of it to improve the looks of a sloppy installation?

Asked by: niagara
I worked in the sheet metal union in Cleveland Ohio and installed a lot of duct work and used a product simmilar to this very often. If we used this in a visible area and one of the apprentices done a sloppy job we put 2" Aluminum Foil Tape over the section to make it look presentable.
Answered by: ChuckTaylor
Date published: 2016-09-27

Is this like putty where you can mold it?

Is this like putty where you can mold it?
Asked by: diy
Answered by: Marty
Date published: 2017-07-21

Do I have to leave the HVAC system off for an amount of time after using the mastic?

Asked by: Dwhite
I'm no HVAC professional, but I would highly recommend leaving the system off and not disturbing the product while it's curing. Integrity and adhesion could certainly be compromised. When in doubt I always error on the side of caution.
Answered by: RaamChamp03
Date published: 2017-07-04

Do you sell this product in red deer ab

Asked by: Chet
Is this product in the reddeer store
Answered by: Chet
Date published: 2016-08-23
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Customer Reviews

Water Based Mastic Half Gallon Tub is rated 3.8 out of 5 by 46.
Rated 5 out of 5 by from This mastic works well I am using this mastic to get all the duct work and plenum sealed prior to blowing insulation into my attic. This mastic product works well to seal HVAC duct work and the plenum. I planned on just sealing a couple seams on the plenum but after checking some of the flex duct connections, I decided to seal every connection from the plenum collar to the vent runs. (Check YouTube videos on "how to seal flex duct ") This will definitely stop the system from sucking dust out of the attic and blowing into my house and will increase overall HVAC efficiency. This mastic works very well, applied with a 1" brush. Wear rubber gloves, gets messy. Water clean up.
Date published: 2014-11-11
Rated 2 out of 5 by from This sealant got the job done but it really doesn't measure up to the quality of other sealants I... This sealant got the job done but it really doesn't measure up to the quality of other sealants I've used. I'm not sure how it will hold up over time but it certainly didn't leave me with much confidence. Other sealant spread and cover so much smoother, thicker and quicker I don't know why HD carries this at all.
Date published: 2016-11-10
Rated 3 out of 5 by from Not HVAC grade I bought a bucket of this stuff in a pinch on the weekend to seal ductboard as part of a coil changeout job. While I can say that it works, it is nowhere near what I expect from an HVAC mastic. It is not fiber reinforced. It doesn't coat as well as real duct mastic. It shrinks and thins a lot when it dries and turns an ugly tan color instead of staying white. It is time consuming to get a "nickel thick" application. I'm comparing it against my experiences with Carlisle CCWI-181. I'm going to have to go back in a few days and go over all of the joints with Carlisle mastic in order to finish the job right. I don't know why HD cannot stock UL-listed HVAC stuff like this. It's not like it cost me any more at the supply house (actually cheaper oz-for-oz).
Date published: 2015-11-19
Rated 5 out of 5 by from Best Sealant Ever I used this EXACT product from Home Depot in 1990 when I redid my condenser duct work. I used aluminum tape at the duct seams and then put on some rubber gloves and hand applied this over all the seams. It stuck to everything, metal, tape, foam insulation, etc. My A/C drip pan just rusted out 10/24/2013 and this stuff was STILL stuck tight and STILL flexible. I used a box cutter and cut this rubbery stuff and pulled on it HARD to get it off. This stuff is still GREAT after TWENTY THREE YEARS!!
Date published: 2013-10-25
Rated 1 out of 5 by from Totally inerfior mastic. Go to an HVAC supply and get some professional mastic (or have it ordered). I got this junk on the weekend because HVAC place was closed. It'll take 4x as long to apply, has poor adhesion, shrinks, cracks, doesn't dry evenly, can't be worked into cracks well, and just seems cheap. It's also more expensive than the professional product I bought from HVAC supply house, which has UL 181 cert, LEED cert, and made my life so much easier. I will give it a "fair" on quality, though, as it would be far far better to use this mastic than the cheap tape out there (Butyl tape would have an edge, but not the foil faced acrylic tape...). I'm actually going to remove some of this stuff and do it over again with the good stuff...
Date published: 2014-11-29
Rated 1 out of 5 by from Poor product. I used this mastic to seal ducts around the plenum of our furnace. It says that is can be spread using a brush so I used a brush. The mastic was so thick and hard that I could not use the brush, instead using my hands with disposable rubber gloves on. Like a clay this mastic balled up and would stick to me much better than the ducts. The next day I went down to check some other things and looked at the mastic. It was all cracked like a dry lake bed. Not a good seal. I would recommend getting Airseal 22. I wish Home depot would carry some quality stuff...
Date published: 2012-10-12
Rated 5 out of 5 by from Tough, tight duct sealant I used this mastic to seal most of my HVAC duct. Simply brushed it on. It creates a very tight and tough seal. Obviously, it also locks the duct in place, i.e., 90 degree adjustable elbows. My only concern about the product is when I have had the occasion to replace duct work. I find the mastic has caused rust under it, but it seems to be surface rust . I hope it is not an ongoing process. Duct is so thin, I would prefer no rust but I haven't found an oil-based mastic. Do be aware that it can be fairly messy and even drippy so protect any finished surfaces nearby.
Date published: 2015-02-25
Rated 5 out of 5 by from good product product works well for sealing up ductwork. the ducts under my house had holes the size of a quarter in every spot where a connection was made. TIP : use mesh drywall tape around the joints, then apply the mastic. works great. easily filled in the holes and gaps I had in my ductwork and supply box
Date published: 2012-06-30
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