I'm going to be installing a TV antenna with a mast.

I want to make sure I ground everything properly. As far as I can tell, I need to ground the antenna via the coax and a grounding block, and then ground the mast separately.

My house was built in 1969 and has no ground rod. The breaker box is in the center of the house and has a ground wire wound round a cold water pipe in a crawl space. This is nowhere near my antenna installation.

I have cable internet. The coax from this is attached to a grounding block, which is in turn attached to the thermal expansion outlet pipe from my tankless water heater.

It seems I have two options. The first is to follow Comcast's lead and use the thermal expansion outlet pipe for everything. The second is to buy one (or two?) ground rods and use them instead.

Which one is correct? Or are neither correct?

Edit: here's a plan view of the current situation: enter image description here

  • 1
    If you drive your own ground rods, you'll have to bond them to the electrical service.
    – Tester101
    Feb 21, 2016 at 4:55
  • You'll have to bond the mast to the electrical services grounding system. You'll have to install an Antenna Discharge Unit (ADU), that also has to be bonded to the grounding system. The coax from the antenna will connect to the ADU, before entering the home.
    – Tester101
    Feb 21, 2016 at 5:01
  • I'm not entirely sure what an " electrical services grounding system" is, but the only grounding at the moment is the copper wire attached to the cold water pipe in the crawl space and the copper wire attached to the hot water pipe on the external wall. Can you be more specific about what I need to do? Feb 21, 2016 at 15:59
  • It's difficult to say for sure without being on site, but it sounds like the main water line is being used as the grounding electrode. So you're going to have to bond the mast and ADU to there. However, without more details, it's difficult to say for sure how to accomplish that. The grounding wire for the mast and ADU has to be as short as practicable (less than 20'), and run in a straight line. There may be a way to install an Intersystem Bonding Termination (IBT) near the mast/ADU, I'm just not sure of the proper way to bond that back to the grounding electrode (water pipe)
    – Tester101
    Feb 21, 2016 at 16:07
  • I've attached a plan view picture (imagine the purple squiggle is a copper wire). If I bond to to the hot water pipe (like Comcast has) I guess it gets to the house ground eventually. Would that work? Feb 21, 2016 at 16:57

1 Answer 1


The main grounding electrode conductor (the wire running to the cold water pipe) is required to be terminated with a ground clamp. Wrapping it around the pipe is not a good connection.

After fixing the ground clamp add an inter-system bonding block to the main ground wire (they sell these and the ground clamps at any big box store). It clamps onto the ground wire without cutting it. It will have a terminal strip for attaching the ground wires from your cable TV and the TV antenna. Attach those there. The cable TV isn't properly grounded either from what you said.

The TV antenna ground wire can't be smaller than #14 AWG copper wire.

This all in addition to the ADU that Tester mentioned.

  • Yeah, the wire wrapped around the pipe didn't look good even to me. Excuse my ignorance, though - why is the existing coax not grounded properly? Doesn't it get to the same place as the electrode conductor eventually? Feb 21, 2016 at 17:26
  • It will work. The new requirements are for all communications to be grounded to the inter-system grounding block. Cable and phone companies never were much for proper grounding.
    – ArchonOSX
    Feb 21, 2016 at 21:02
  • There should be a bond jumper across the water heater for the continuity of the grounding electrode system. Normally, you are supposed to bond to the water pipe within 5 feet of its entrance to the building and jumper the water meter if there is one between the bond and the entrance.
    – ArchonOSX
    Feb 21, 2016 at 21:07
  • There's no jumper across the water heater. I guess I'd better add one fairly soon. Feb 21, 2016 at 21:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.