I am bringing up this old post only to tell you what the local inspector required when I installed a new whirlpool bath with heater in a house with copper piping. This was a new inspector, just of college with a four-year electrical engineering degree but little or no practical experience with home wiring. (He saw the dead-front GFI's I was using and thought I had somehow filled up the plug slots on them! He also had never seen the 12 - 2 - 2 w/g wire I ran from the breaker box to feed the pump and heater from separate breakers.) He later admitted that he thought the job of inspector would be easy since he only had to follow the NEC, but now realizes that the application of these guidelines is not as easy as he had expected. Still, he listened carefully to my comments and concerns, and did not have the "I'm the expert here" attitude I have had with other inspectors.
According to the directions for my new whirlpool tub (and confirmed with the American Standard help line), the lug on the whirlpool motor is to be used to bond the heater (if used) to the whirlpool motor. The heater also has a ground lug on it, and the directions call for a #8 or larger copper wire from the bond screw on the heater to the bond screw on the pump. American Standard even ships a short length of #8 solid uninsulated wire for this use. However, they also state in a disclaimer that all wiring must conform to the local requirements.
My issue was that traditionally the local authority wanted the pump lug bonded to the incoming (metal) cold water pipe. (This was included in a notebook of "issues and decisions" the previous inspector gave to the new one when he retired.) If piping had been all plastic in the house, this would not be required. He also insisted that the heater lug also be bonded to the cold water pipe. (The "bond everything" philosophy mentioned in an earlier post.) However, he also insisted that the directions of the manufacturer had to be followed, which said I had to run a bond from the pump to the heater directly. At issue was the fact that the heater lug can only accommodate a single #8 copper ground wire, so it is impossible to have two ground wires attached to it (as the inspector wanted). He would not buy off on changing the lug since it was part of a factory engineered system, unless American Standard offered a suitable replacement part.
Finally, he came out and we discussed the issue. He said he would accept two bonding arrangements, provided all ground wiring was #8 copper or larger.
1 -- A separate bond wire from the heater to the water pipe connector and another from that same water pipe bond to the pump. OR 2 -- A wire from the heater to the pump, and then from the pump to the copper water pipe bond. This could have been done with a single continuous wire, but the location and design of the lug on the pump prevented the wire from passing through from one side to the other -- so a second wire would be required. He would accept using a second wire provided the lug on the pump was "Listed" for at least two #8 wires. While there was room for two #8 wires on the pump, it was not marked in any way so he said the installation instructions which implied only a single #8 wire in this lug precluded the use of two wires in this lug. Nobody at American Standard could provide me with "Listing" information on the lug, since they said it was not needed on the lug since the entire pump assembly, including the lug was listed as a unit. This forced me to use the first arrangement.
My point in this post is to reinforce that while the NEC does include sections about grounding and bonding of whirlpools, the exact means are still subject to interpretation and the preferences of your local inspector. Like most regulatory documents, the NEC is a work in progress, and as new technologies and materials become available, it takes time to develop all-inclusive details on how these things should be used.