Ask Dr. Dave: Is there an adhesive that will seal pinhole leaks?
Dave Dunn's March 2019 column.
We have some pinhole leaks in an old fire sprinkler system in a large apartment block. Is there an adhesive that will seal those leaks?
Some people use patches on the outside of the pipes to solve the problem, such as an epoxy putty. However, this is only a temporary solution, and it is difficult to apply inside the walls of a building. Recently, a system has been approved to comply with the international fire code that involves using a two-part epoxy system that is mixed, blown into the pipes and forms a continuous sealant/coating on the inside of the pipes. Not only does this seal the pinhole leaks, but it also provides protection against future corrosion of the pipes and subsequent new pinhole leaks. Such a system often will give several years’ service before the pipes need to be replaced and is much more cost effective than pipe replacement.
The system involves drying the pipes with heated compressed air and then abrading the surface to ensure good adhesion, followed by blowing the mixed epoxy into the pipes. The International Code Council and large cities like Los Angeles have approved such a system as part of their plumbing programs. To comply with the international fire code, testing includes the severe Fire Test in UL 852, where coated pipes fitted with sprinkler heads are exposed to real fires with temperatures exceeding 1,600°F. The coating must be intact after the testing with no observations of cracking, flaking or other deformation of the lining material, and no fragments from the epoxy can negatively impact sprinkler flow.