How far from the edge of the pool to cut open concrete deck?

I have a 18x36 vinyl in-ground pool constructed approximately 28 years ago and surrounded by a concrete deck. It's leaking on the return side and I'm thinking about repairing it myself. There is evidence of a previous repair where they cut a square out and rerouted another line back to the pool house. I thought I'd start there but if I don't find it there my thought is to open up a hole by the return fitting(s) to see if there a problem with those connections. If not I can then pressure test each section to isolate the section. Before I start cutting I was wondering if anyone knew how far back from the edge if the pool I should stay (how thick is the wall on average) I believe its a cement base but again was hoping someone could tell me based on the age and pictures what was normal back then. If all else fails I'm considering running flexible PVC through a trench cut in the concrete. In the mean time I have run a surface mounted ABS line to bypass the returns. Any advise is most welcome.
Pictures: https://picasaweb.google.com/radices...eat=directlink

Anybody able to help this poster?

Welcome to the Forum!

I don't know how I missed this:confused:

I'd stay 6" off the coping, just to be safe. It's easy enough to dig the 6" under the deck to check the inlet and the threaded connection.:)