Dspark, the reason that the h2o is according to 250-66, and not allowed smaller is in the fact that a mettalic water pipe system IS the lowest impedance electrode usually avaliable. ( with Ufer's a close second)
the NEC does not, however, differentiate bettween a city system and an isolated residential system .
[This message has been edited by sparky (edited 06-05-2001).]
