SEAL-TYTE Boiler Sealer

Liquid boiler sealer for all steam systems.  SEAL-TYTE is recommended for sealing leaks in new or old low pressure steam boilers including all one or two pipe house heating systems, and vapor vacuum systems. SEAL-TYTE saves time and money in repairing small leaks caused by sand holes, defective castings, and imperfect pipe threads.  The sealer can also be used in sealing leaks above the boiler water line (See the Directions for Use).  SEAL-TYTE prevents the formation of scale and rust which can both decrease boiler efficiency and increase fuel consumption. This unique pressure sensitive product is formulated to go directly to the source of the leak and quickly seal without gumming up zone valves or other working mechanisms. SEAL-TYTE is designed to seal leaks, while conditioning and lubricating the system for top performance.  Due to SEAL-TYTE’s superior strength, boiler systems require less SEAL-TYTE than most all other sealing compounds on the market. See SEAL-TYTE Boiler Sealer recommendation chart.

SEAL-TYTE will mix instantly with the water in the boiler. When water in the boiler leaks through the crack or fault in the system, the mixture will begin to vaporize. The oxygen in the air will create a reaction with SEAL-TYTE, which will cause it to form into a solid. The heat from the boiler strengthens the reaction, further reinforcing the seal. Once the reaction is completed, SEAL-TYTE will expand and contract with the metal of the boiler.


Approximate BTU Equivalent
Boiler Rating Square Feet of Steam
SEAL-TYTE Required (Quarts) 
350 85,000 ½
600 144,000 1
1,200 288,000 2
2,400 576,000 4
3,000 720,000 5
8,000 1,900,000 8
12,000 2,880,000 10
15,000 3,600,000 12
20,000 4,000,000 16
50,000 12,000,000
Number of
Square Feet of
1-4 800 1
8 1,200 2
16 2,200 3
30 4,000 5
70 10,000 8
120 17,000 14


SEAL-TYTE fills and seals holes and cracks in steam boilers.  If the leak is excessively large, seal cracks on the boiler with Heat-Tyte Furnace Cement and seal threaded joints with Steel-Unyte Thread and Gasket Sealer.

Not for use in boilers containing anti-freeze.

Made in the U.S.A.

Safety Data Sheets


Spec Sheets

Product Name Product Code Size Container Items Per Case Case Weight UPC Code
SEAL-TYTE STS32 Quart (.95 L) Plastic Jug w/ Spout 12 40 lbs. (18.1 kg) 688544320350
STS1 Gallon (3.785 L) Metal Can w/ Handle 4 46 lbs. (20.9 kg) 688544010350


  • BOILER-AIDE 2-N-1 All Purpose Boiler Cleaner and Treatment
  • FREEZE-FIGHTER Anti-Freeze Concentrate
  • FREEZE-POINT-100 Anti-Freeze Solution
  • FREEZE-POINT-100 Anti-Freeze Solution
  • HEAT-TYTE Furnace Cement
  • TALON Epoxy Putty