Negative ground for new External Pump Install

[PRW]

Hi All,
I'm about to replace the submersible pump with an external Shurflo. Read through various posts on here and other forums to work out the procedure. However, there's differing scenarios of how to attach the -ve ground wire from the new pump to the existing system depending upon your van model & layout etc. This is due to accessibility of the existing ground wire for the existing submersible pump.
In my system I'm removing the existing whale pressure switch and fitting the Shurflo pump in its place. The +ve wire from PSU via EC700 to the pressure switch can simply be re-used and connected to the +ve wire on the new pump. However, the ground wire in the existing system is inaccessible due to its location.
Others who've had the same problem have found another ground to use. I have two options and wanted to ensure my thinking was sound.
Option1: Nearby is the solenoid and electrical connection for the Whale automatic filler socket. Thinking is to use a piggyback spade connector on the -ve connection here in order to connect the -ve wire from the new pump.
Option2: The original Solar controller has been removed and new SC put in place with it's separate wiring bypassing the Sargent EC700. However, the original wiring that connected the original SC to the EC700 is still in place. There is both a +ve and -ve wire and both are no longer used but still connected to the EC700 (fused at 10 amps for this connection). Thinking is to use the -ve wire as the ground for the Shurflo pump.

Are both options valid and anything else to consider?

 

[pappajohn]

Any earth will do.
I would use both pos and neg from the old solar controller as the wires from the old pressure switch may be too thin for the currant a pump can draw.
But....you do need a means of turning off the pump if needed

 

[ctc]

Use some contact paste, stops the connections corroding so quickly.

 

[PRW]

Any earth will do.
I would use both pos and neg from the old solar controller as the wires from the old pressure switch may be too thin for the currant a pump can draw.
But....you do need a means of turning off the pump if needed

Thanks for the confirmation. I could use the wires from the old pressure switch as it's fused for 10 Amp, well within the limits of the new pump, however I think your suggestion of using both wires from the old solar controller is a neater solution which I hadn't considered.