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Master Flow

Model # WBA50

Internet # 100396973

Store SKU # 559722

Water Based Mastic Half Gallon Tub

This item has been discontinued.
The Home Depot no longer carries this specific product.

$11.95 /each


Model # WBA50

Internet # 100396973

Store SKU # 559722

Store SO SKU # 755578

Master Flow Water Based Mastic is a water-based adhesive that creates an air-tight seal on duct seams and joints. By eliminating air leakage, sealant increases the overall efficiency of the duct system, which can cut energy costs. Available in tubes or tubs.

  • Meets or exceeds most energy codes
  • VOC content is 18.5g/l
  • Seals duct systems to eliminate air leakage and conserve energy
  • Use where ever duct fittings connect
  • Always insulate ductwork for greater system efficiency and comfort

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.) 
5.7 lb 
Warranty / Certifications
Manufacturer Warranty 
Free from Manufacturer Defect at Time of Delivery. 


Rated 3.7 out of 5 by 38 reviewers.
Rated 5.0 out of 5.0 by 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. November 11, 2014
Rated 5.0 out of 5.0 by Best at what it does! For nearly a hundred year old home with some pretty old duct work, we were heating and cooling our basement as opposed to the rest of the home. Duct tapes didn't hold up well and new air leaks would form sooner than expected. The mastic did a great job at durably holding up and sealing. Since it was an unfinished basement space, we weren't so concerned with the, shall we say, less than aesthetically pleasing final look. January 14, 2014
Rated 5.0 out of 5.0 by 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. February 25, 2015
Rated 4.0 out of 5.0 by Good duct sealant Purchased to seal dust collection ducting. Worked very well. August 11, 2015
Rated 5.0 out of 5.0 by Good product I like the way the product is packaged, easy to store on our trucks. So far it has held up good on our hot trucks. Still does a good job. August 4, 2015
Rated 5.0 out of 5.0 by 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!! October 24, 2013
Rated 5.0 out of 5.0 by Great Purchase Easy to apply with my hands, a better visual for thickness of application is about a nickel thick. Does a great job. January 31, 2015
Rated 1.0 out of 5.0 by 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... November 29, 2014
  • 2015-08-29T12:15:28.645-05:00
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