Our house was built in 1997. The pipes are copper (including the city water supply pipe). Some time after the house was built, the previous owners installed a water softener. The softener parts are all plastic, so the city water supply is not part of the grounding path.
I dug up the installation manual for my softener (Kenmore Ultrasoft 100), and it says to bond the softener in/out pipes to provide a grounding path. This has not been done. It has been this way for ~10 years.
There is already a solid copper wire clamped to the cold water pipe that runs over to the breaker box. (This wire is attached to the plumbing after the softener.) Not sure the gauge of the wire. Presumably this wire grounds the cold water pipes. I would guess there is a grounding rod somewhere behind the breaker box, but I have not verified this.
Edit: Because of this grounding wire, it seems most of the cold water plumbing is already grounded. The only part that isn't bonded is the ~5ft of cold water pipe that comes into the basement before the softener.
I do believe my outlets are grounded because the "Ground" LEDs on all of my surge strips are lit.
Should I follow the softener manual's advice and bond the water softener in/out pipes?
If the breaker box is already grounded via a grounding rod, would this extra ground path hurt anything? It seems like a good idea to have second path, in case something happens to the first one.
However, I am not sure about the difference in potential between the two ground points. Could this cause a problem? (For reference, the cold water supply line is ~50ft from the breaker box.)
Follow-up question: Should I bond the hot water pipes to the cold water pipes? There seems to be some conductivity between the hot/cold pipes already (checked with a multimeter), but I can't find an actual bonding wire anywhere, so I may just be seeing some incidental conductivity via the water heater or faucets.