Failing to cap a crack properly before injecting epoxy resin can cause a leak that wastes costly resin. Why do setups leak? Usually it's because of incorrect capping methods. Using the right method prevents leaks.


  1. Clean the surface: To bond well, caps must be applied to a sound, clean surface.
  2. Select the right cap material: For most work, a high-modulus, gel-type epoxy should be used. Also, a fast cure time--2 to 3 hours--is desirable if you want to cap and inject epoxy on the same day.
  3. Carefully batch and mix the epoxy cap material: Accurately batch the two components for the cap. If the ratio is off by 10%, presume that the strength will be short by at least that much.
  4. Avoid skips and thin spots in the cap: Skips are areas at the surface of the crack where the cap doesn't bond. These voids allow injection resin to flow under a larger area of the cap, often lifting it off and causing a leak.