SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

The setup is this, The pump, pump start relay, and existing controller are all next to the water source, a pond. It is a 10 acre piece of land that has all been irrigated except for behind the homeowners house. App. 4 rotor zones and a drip zone are needed.
The house and the pond are on opposite ends of the property, quite a distance. I can get the water I need from the closest valve manifold located in the front yard of the house. Whoever installed it ran 2 ea. 13 strand, 18 guage multi-strand and I have access to two spare wires in that manifold as well.

I was wondering if I could use one of those spares for the pump relay and mount a second controller on the house to accomodate the additional valves i need to install. Will power run back through the existing wire hooked to the relay and possibly back into the controller at the pond. The alternative is to use the existing controller (there are 6 open terminals) and pull wire a very long distance.I'm just concerned of the possibility that I may fry that expensive controller. Wanna do the right thing.
Thanks in advance for any thoughts. Hope I worded it so the question is understandable.

Thank you sir for the response. I'm not familiar with much of the golf course type pump systems technology.. I get conflicting answers from my suppliers and nothing concrete. Have a good friend that worked on irrigation on golf courses for many years and I will call him tonight. Sounds like it might be as cost effective to pull the wire I need. It's a ****uva distance. I just need to put real options into the hands of the homeowner.

Thanks again for your response.