American Polywater® FST™ Foam Duct Sealant

Protect Your Cable Runs with Closed-Cell Foam

Low Price Guarantee


What's special about this foam duct sealant?

  • Made to keep water, sewer gases, and rodents out of conduit for safe cable runs
  • Compatible with all types of cables and conduit, great application flexibility
  • Designed for harsh environments and permanent or semi-permanent applications
  • Holds 15 ft water-head pressure for an extended period of time while keeping your cables safe
  • Click for More Features
Made in USA

Running cable run in a hostile environment is no easy task. Sometimes conduit, no matter how rigid, is simply not enough protection for your cables. Water, gas, and even rodents can get into the conduit and damage your wires if the conduit is not properly sealed. FST Foam Duct Sealant plays a key role in such applications by completely sealing conduit, equipping it to handle events that most open-cell canned foams can't protect against.


AP-FST-250 FST Duct Sealant 8.5 oz Caulking Tube Style 
AP-FST-250KIT1 FST Duct Sealant 8.5 oz Caulking Tube Style - KIT
AP-FST-DAM 24" Foam Damming Strip
AP-HP-P158ID Conduit Pre-Treating Cleaning Wipe

  • Great adhesion to metals, plastics and, PVC, for a firm grip and tight seal
  • Easy to remove in case the need for a new cable run arises
  • 8.5 oz tube works with a regular caulking gun for easy application
  • Foam tolerates cable movement, allowing for removals if necessary
  • Quickly expands and cures even in the presence of water, reducing application time
  • Once cured, foam is strong, resilient and chemically resistant
  • Made in the USA USA


FST-250KIT1 includes:

  • (1) 8.5-oz Two-Part Foam Sealant, caulking tube style (FST-250)
  • (4) 24" Foam Damming Strips (FST-DAM)
  • 3 Mixing Nozzles
  • 1 Pair Disposable Gloves
  • 1 Positioning Rod for foam dam
  • 1 Pre-Treating Wipe (HP-P158ID)
  • 1 Resealing Cap
  • 1 Instruction Sheet


Foam Duct Sealant Specifications (PDF) PDF


Cured Properties
Appearance Light yellow color with small, even cells
Closed Cell Percentage 98%
Density 6 lbs/cubic ft.
Compressive Strength (ASTM D1691) 330 psi
Tensile Strength (ASTM 1623) 270 psi
Flexural Strength (ASTM D790) 460 psi
Seal Strength Water 40 feet intermittent - 15 feet continuous
Seal Strength Air >5 psi


CURE RATE - Reaction Time (minutes)

MATERIAL 40° F (4° C)  70° F (21° C)
Foaming, Expansion Complete 8 - 9 minutes 4 - 5 minutes
Hard, Non-Sticky Skin Formation 15 - 18 minutes 7 - 9 minutes






Q:Polywater FST 250

I have three 3" pipes to seal with cables. Will one FST-250Kit1 be sufficient? Do I also need the Tool-250 or do I use a caulking gun?

Asked by Anonymous user on


  • - Thank you for your question. One kit should be enough and yes you can use a regular caulking gun.

    Fernando M. on

Do you have any question about this product?
Let our experts and customers resolve all your doubts

Did you know that we can give you a quote for most of our products, including shipping?

You can also call us toll free 866.222.0030

What can make this page better?

We do everything we can think of to provide you with the product specs, images and ordering info you need, but if we're missing something or still have room to improve, please let us know. Your comments, suggestions and questions are the best tools we have for serving you better!