One of the consequences of over specialization is that in areas where disciplines overlap things may be omitted.  One example of this is the bonding of metal systems to the electrical grounding system in the home.  Without getting overly technical regarding "grounding" and "bonding," every home has a grounding system and all metallic systems in the home (metal  water supply pipes, metal drain pipes, metal heating pipes, gas pipes etc.) must be "bonded" to the house grounding system.  This prevents life threatening shocks to persons touching these systems if the pipes were to become energized for some reason.

     In older homes where the original drains and water supply pipes are metal, problems can arise when the pipes are replaced.  In the picture below we see the bonding clamps that connect the galvanized drain and the two abandoned clamps that should have been re-installed on the new copper supply pipes (above and not in the picture).  But, because plumbers are not electricians it didn't get done.

     A much more serious, but similar issue is when the old galvanized water pipe from the street is replaced with plastic pipe.  If that pipe was the entire grounding system for the house (no ground rods etc), the only path to ground becomes the service support wire and back to the transformer ground.  When the water supply to the home is replaced with plastic it is very important that proper grounding of the house electrical system be verified, maintained and/or upgraded for electrical safety. 

     Replacement of any of the house plumbing with plastic can negate the continuity of the bonding of the metal pipe system and continuity must be restored by means of metallic jumpers across the plastic component (I will save this issue for another blog).

Charles Buell

www.buellinspections.com