Bonding of Metal Water Piping

[Dennis Alwon]

The pipes are currently bonded, via the bonding jumper from the switchgear to the water meter. Once the copper pipe water mains in the building are replaced with CPVC, the water piping in the dwelling units will not longer be bonded. Hence having to add a (3/0) jumper along the CPVC piping, to bond all of the copper stubs running into the dwelling units.

I get it but in one case you are using the street copper lines as a grounding electrode and the other case, where the copper is replaced outdoors, you are just bonding the copper pipes that could potentially get energized.

 

[iggy2]

No copper being replaced outdoors. The incoming water service piping (what ever it is...) will remain. It is just the water mains running through the building that are getting replaced. They run in the ceilings on the second floor corridor. 3/4" stubs come off the hot/cold mains to feed 4 apartments.

 

[wwhitney]

3/4" stubs come off the hot/cold mains to feed 4 apartments.

3/4" copper has an OD of 0.875" and an ID (if type L) of 0.785". As such it has a copper cross-sectional area of 875^2-785^2 = 149.4 kcmil.

That makes bonding it with 3/0 copper (167.8 kcmil) less ridiculous than I thought before doing the above computation.

Cheers, Wayne

 

[Dennis Alwon]

No copper being replaced outdoors. The incoming water service piping (what ever it is...) will remain. It is just the water mains running through the building that are getting replaced. They run in the ceilings on the second floor corridor. 3/4" stubs come off the hot/cold mains to feed 4 apartments.

I get it now. That changes things, imo, bonding the water pipes is not necessary since it is not a complete metal piping system.

 

[augie47]

I get it now. That changes things, imo, bonding the water pipes is not necessary since it is not a complete metal piping system.

I'm slower than Dennis.. From reading the posts I "don't get it". If the interior piping system (above ceiling, etc) is metallic, IMO, it needs bonding. IF ONLY the stub-outs at fixtures (water heater, sink, etc.) are metallic then I agree.. no bonding needed at all

 

[LarryFine]

No copper being replaced outdoors. The incoming water service piping (what ever it is...) will remain. It is just the water mains running through the building that are getting replaced. They run in the ceilings on the second floor corridor. 3/4" stubs come off the hot/cold mains to feed 4 apartments.

Are (or will) the supply ends be accessible where the new CPVC will transition to the existing copper?

If so, you should be able to tie to each units copper pipe there, and run back to the building's service.

You might need small access panels if the transitions would otherwise be covered by building finish.

 

[wwhitney]

Are (or will) the supply ends be accessible where the new CPVC will transition to the existing copper?

Obviously they will be at the time the CPVC is being installed. Good point about the access panels.

I think the OP's complaint is that if hundreds of feet of CPVC pipe are being installed (as I gather will be), then hundreds of feet of 3/0 copper will need to be installed. Basically running a 3/0 copper "bus" in parallel to the new CPVC pipe. Which seems like a bit of overkill, sizing all bonding jumpers based on the service size, vs say the sum of the sizes of the feeders to the 4 apartments that each newly isolated section of metallic piping would serve.

Particularly as if they were replacing a bit more copper pipe, so that now each apartment would be an isolated system, then the bonding jumper for an individual apartment could be sized based on the feeder size to that apartment, per 250.104(A)(2).

Cheers, Wayne

 

[Dennis Alwon]

I'm slower than Dennis.. From reading the posts I "don't get it". If the interior piping system (above ceiling, etc) is metallic, IMO, it needs bonding. IF ONLY the stub-outs at fixtures (water heater, sink, etc.) are metallic then I agree.. no bonding needed at all

I read it as the water lines in the ceilings on the second floor were being replaced with plastic. This creates 2 partial systems, one which is plastic and then changes over to copper. That isn't, imo, a metal piping system.

 

[LarryFine]

Obviously they will be at the time the CPVC is being installed. Good point about the access panels.

Thank you.

Particularly as if they were replacing a bit more copper pipe, so that now each apartment would be an isolated system, then the bonding jumper for an individual apartment could be sized based on the feeder size to that apartment, per 250.104(A)(2).

That's what I'm thinking; the greatest current that could energize each unit's piping.

 

[wwhitney]

I read it as the water lines in the ceilings on the second floor were being replaced with plastic. This creates 2 partial systems, one which is plastic and then changes over to copper. That isn't, imo, a metal piping system.

The ceiling in question I understand to be the common hallways. Each apartment has an entirely metal water pipes (and each apartment will still be interconnected by metal water pipes to 3 other apartments). That's not a metal piping system?

Cheers, Wayne

 

[mtnelect]

The ceiling in question I understand to be the common hallways. Each apartment has an entirely metal water pipes (and each apartment will still be interconnected by metal water pipes to 3 other apartments). That's not a metal piping system?

Cheers, Wayne

It's back to plan "B".

"Also, in buildings of multiple occupancy where the metal water piping system(s) installed in or attached to a building or structure for the individual occupancies is metallically isolated from all other occupancies by use of nonmetallic water piping, the metal water piping system(s) for each occupancy shall be permitted to be bonded to the equipment grounding terminal of the panelboard or switchboard enclosure (other than service equipment) supplying that occupancy. The bonding jumper shall be sized in accordance with Table 250.122, based on the rating the overcurrent protective device for the circuit supplying the occupancy".

 

[wwhitney]

It's back to plan "B".

"Also, in buildings of multiple occupancy where the metal water piping system(s) installed in or attached to a building or structure for the individual occupancies is metallically isolated from all other occupancies by use of nonmetallic water piping, . . ."

The issue is that if "occupancies" means "apartments" for an apartment building, then each apartment will not be metallically isolated from the others. Rather, they will be metallically connected in groups of 4.

Cheers, Wayne