You'd be better off with a proper, separate grounding of the SAT equipment. That means a ground from the dish itself and grounding blocks for each coax at the home entry point, in accordance with the NEC and any other local codes that may prevail. Check this link, pg. 31 (pg 35. of the pdf file)...
PS - Don't ground to any pipe you're not absolutely sure about! Use only a cold water pipe on the entrance side of any meter or other equipment. Depending on your geographic location, it's unusual for a water pipe to run through an attic due to the freezing possibility. The one you mention is probably a waste line vent...
PPS - Look at the second sheet in the pdf file where it mentions grounding the dish itself. This is also important. They show an example on pg. 30 of the manual (pg 34 of the pdf). I just ran a 10-gauge copper wire from a mounting bolt on the dish itself alongside the coax cables to the cable grounding block for that part. That should all be protected from corrosion with silicone grease or sealant, etc.
