Masthead 1
Masthead 1
Masthead 1
Masthead 1
Masthead 1
Masthead 1

Hydro-Seal 75

For examples of Hydro Seal 75 in use, visit our photo gallery.

For a comparison of kits sizes, click here.


Hydro Seal 75Hydro-Seal 75 is a high strength, hydrophobic, breathing type, two-component, modified epoxy coating manufactured from a balanced ratio of fillers, and water extended resins and hardeners. Our exclusive formula combines flexibility with the hardness of epoxy resins.

During the curing phase, Hydro-Seal 75 polymers cross-link to create a macromolecule of extreme durability to provide optimum resistance to a wide variety of chemicals, severe below grade hydrostatic pressure, and other environmental conditions.

The Hydro-Seal 75 mixture penetrates deep into the surface capillaries, that when totally cross-linked, serve as a water insoluble lining on the sidewalls of the pores and voids in the substrate making them water repellant. This lining robs the water of its capillary action preventing moisture from entering through the masonry. Successive coats, each bonded to the previous coat, build up sufficient density, cohesion and strength to render the surface pinhole free and impervious to mass water penetration.

Physical Form

Hydro-Seal 75 is a heavy bodied, organic, solvent free, odorless, non-flammable, relatively non-toxic two part epoxy that is packaged ready to use in two equal component packages marked component A and component B.  These components are blended together just prior to use in equal proportions.  The colors range from standard white, gray and beige, to customized pastels.


Formulated for on site, two-coat spray or roller application, Hydro-Seal 75 forms a positive, high quality, integral protective barrier against mass water penetration. When minimum down time, high pressure resistance, coating strength and longevity are major factors in choosing coating suitability, Hydro-Seal 75 can be specified for use on all types of damp interior or exterior, above or below grade masonry surfaces including concrete, brick, various types of masonry block, mortar, stucco, adobe, cast-stone, or sandstone.



  • Wet leaky basements
  • Exterior Masonry
  • Foundations
  • Elevator Pits
  • Interior Masonry
  • Concrete Flooring
  • Swimming Pools
  • Plywood Floors and Decks

Protective Coating

  • Bridges
  • Concrete Slabs
  • Highway Barriers
  • Sewer Treatment Tanks
  • Manholes
  • Stucco
  • Chemical Containment area

Patching, Resurfacing

  • Crack Filling
  • Old Foundations
  • Floor Resurfacing
  • Floor Cove
  • Seawalls

Although the resulting finish may be installed as its own opaque decorative accent coat, Hydro-Seal 75 can also be installed as a masonry primer for a wide variety of coatings and finishes. Due to its exceptional durability, non-lift characteristics, high alkali-chemical and water resistance other coatings will have no effect, and will bond tenaciously to the prime coat of Hydro-Seal 75.

Hydro-Seal 75 is ideal as a multi-purpose material for renovation of old buildings or other edifices.


White Standard Grey
WhiteStandard GreyGrey


  1. Resists Hydrostatic pressure Interior, below grade walls with stands hydrostatic pressure of over 40 PSI without leaking, exceeding Federal Specification TT-P-001411.
  2. Water Resistance Will effectively protect substrate and prevent the absorption of exterior moisture as tested using Wind Driven Rain Machine in accord with Federal Specification TTC-001224
  3. Efflorescence Control The passage of water through masonry units dissolves free lime and other salts including sodium, calcium or potassium, carrying them to the outer surface. The salts then crystallize to form efflorescence, an objectionable discoloration of the surface. Hydro-Seal 75 prevents the major cause of efflorescence deposits.
  4. Alkali Resistant Excellent resistance to alkalis in accord with ASTM D-543.
  5. Non-Oxidizing Does not contain silicone or oxidizing ingredients such as marine oils, or vegetable oils. Will not oxidize in accord with ASTM D-822.
  6. Flexibility Retains ability to flex with movement of the structure. Passes 1/8th” Mandrel test as per ASTM D-822
  7. Solvent Free Contains water extended resins that cure by catalytic polymerization.
  8. No unpleasant odor Since there are no toxic or odorous solvents in Hydro-Seal 75 it can be used in occupied areas with no discomfort including schools, homes, and hospitals. It is also ecologically safe and acceptable.
  9. USDA Approved Hydro-Seal 75 is USDA Approved for use in food preparation areas.
  10. Vapor Transmission Does allow some vapor transmission in accords with ASTM D-1653. Perm 1.75
  11. High Solids Solids are 56% by volume. The high resin filler ratio give Hydro-Seal 75 superior waterproofing properties over a prolonged period of time. Thixotropic additives allow for uniform vertical spray applications with high film builds up to 30 wet mils without sag, surface checking or mud cracking.
  12. Labor Saving Sprayed with a minimum 2/3 gallon per minute capacity pump (Graco 433 or equal). Use a minimum .019 or .021 tip and 3/8” I.D. material hoses.
  13. Cleanable May be easily cleaned with normal cleaning compounds.
  14. Fast Dry @ 72 degrees, 50% relative humidity Hydro-Seal 75 sets to touch in one hour; dries hard in 3 hours - with a total cure in four days.
  15. Pot Life Mixed material will last about 45 minutes @ 72 degrees.
  16. Shelf Life Hydro-Seal 75 will last 6 months in unopened containers.


This chart assumes the masonry to be in good general condition. Old masonry, however, often becomes more porous after long exposure and weathering. Steam cleaning, sandblasting, and acid etching will also make masonry more porous. These recommendations will have to be adjusted on the job to the condition of the masonry. When estimating coverage, allow 10% for overspray. Winds of over 15 MPH will result in further loss of material.

Lightweight block, Cast-stone, Sandstone, Open textured block 50 - 100
Concrete, concrete block 100 - 150
Stucco 130 - 190
Clay Brick (porous) 60 - 110
Clay Brick (dense) 100 - 150
Cement Asbestos Products 75 - 100
Concrete (dense) 175 - 250
Plywood 100 - 130


Hydro-Seal 75 is available in 10 gallon kits (2 five gallon pails marked A and B), 6 gallon kits,  1 gallon kits and in 55 gallon drums. Colors available include white, gray and beige.


This material should not be applied at temperatures below 50 degrees. Do not apply if there is a threat of rain within three hours of application. Hydro-Seal 75 should not be applied over other paints or coatings.

General Precautions

Do not mix more material than can be applied in 40 minutes @ 72 degrees. Warmer temperatures will decrease material pot life. Under no circumstance should the mixed material be tempered by adding water. Clean tools, hands, spillage or drippings immediately or it will be extremely difficult to remove.

Surface Preparation

See manufacturers general preparation and application instructions for recommendations on preparing different substrates. For new or uncoated masonry wash surface with Tri-Sodium-Phosphate to clean and open up the surface to accept the prime coat of Hydro-Seal 75. The concrete can then be neutralized with clean water. Pools need to be acid etched and neutralized before Hydro-Seal 75 can be applied.


Before treating interior below grade walls it may be necessary to relieve excessive hydrostatic pressure by drilling through concrete block at the base of the wall. Once all the water has drained out of these holes, and the Hydro-Seal 75 has been installed, the holes can be filled with Hydro-Epoxy Mortar (a mixture of Hydro-Seal 75, dry cement and sand). In some cases, if this is not done, Hydro-Seal 75 can be washed away before it sets and bonds. Excessive wet surfaces will result in an over thinning of Hydro-Seal 75.


Hydro-Seal 75 is a two-component material that requires the mixing of an A and B component together. Care should be taken to mix each part in their own independent container before blending them together. Try to always mix the B component into the A component.

Hydro-Seal 75 is a one to one ratio mix, it is easy to use by simply mixing equal amounts of the A and B together.

We recommend mixing material with a Jiffy type mixer or power drill (not over 150 RPM) with a basket or “T” type mixing blade. Care should be taken to mix the base and the catalyst for three minutes or until the material reaches the consistency of heavy cream.

Bonding Mortar

Hydro-Seal 75 can be combined with different Portland cement mixes to create a trowel applied smooth mortar. This material makes an excellent crack filler, leveling or tuck pointing material for masonry joints. Hydro-Seal 75 Epoxy Mortar possesses tenacious bonding qualities as thin as required.


Northern Industries Inc. warrants that Northern Industries products will be free from manufacturing defects and conform to specifications. Sellers make no other warranty, expressed or implied, and all implied warranties of merchantability and fitness for a particular purpose are hereby disclaimed.

Due to a lack of control, Northern Industries Inc. will not assume liability or responsibility for installation. No representative, distributor, or approved applicator of Northern Industries Inc. is authorized to change or modify the date or standard warranty in any way, or add conditions, provisions, and/or amendments to the sale.

Buyers are urged to read the data outlined to assure product matches proposed application, and are encouraged to call Northern Industries Inc. with any questions. All other information supplied by Northern Industries Inc. is considered accurate but is furnished upon the expressed condition that the person receiving it shall make his own test to determine its suitability for his particular purpose. Warranty is limited to replacement of product.