|I am planning to put a Diamond D130 discone on the roof, supported by a tripod and a 6' black iron pipe. The question here is mast grounding. The location is not anywhere close to the house grounding rod. Would it be OK to ground to the cleanout cap of the sewer line? The line is cast iron, buried, and runs under the ground 30' to the septic tank. The cap is exposed and it would be relatively easy to drill a small hole into the cap, which is just about directly under the antenna near the house foundation.