Folks:
w_tom is slipping. I keep throwing random refs to surge protectors into Usenet and private-forum posts, and he never comes in to reply. Such neglect.
Correct me if I am wrong, but there was a time when the NEC allowed one to ground equipment to a nearby water pipe. Of course, there was also a time (look at the 1899 code, which is posted online somewhere) when they allowed one to use a gas pipe as a grounding electrode. The time for either of those is not today.
Back when men were men and jackets were braided, one could safely assume that all pipes were metal. Metal pipes full of water from the ground to the might well provide a nice low-impedance path to ground. But we can't assume that now. My own house has all metal pipes. Were I to open up a 2nd floor wall, and install a ground clamp on a cold water pipe, and test the ground, it would probably be excellent. But then the wall is closed, the clamp forgotten.
Down the road, somebody replaces sections of the copper cold water pipes with plastic. Now I have a ground connected to a pipe, connected to nothing, and unless somebody tests the ground before and after plumbing, nobody is going to know about it. One day there is a direct short to ground. Fixtures have been replumbed with plastic supply connectors, except one old sink with separate hot and cold faucets. The cold faucet is now hot. The hot faucet is still bonded to ground at the water heater. Somebody turns one on, and reaches for the other...
In any case, a falsely advertised ground is bad enough; a ground that goes to unbonded metal is worse, and that's what grounding to a water pipe can get you. Sometimes I see washers or dryers that had been grounded to a nearby pipe. This isn't as bad in an unfinished basement; you can see all the pipe, but it's also the situation where putting in a run of grounded cable and a new receptacle is very easy.
Besides, if you're going to pull a single conductor into a space, you might as well pull in a cable, as somebody up there pointed out.
G P