Other than a chain saw is there an easy way to remove the sprayed on foam?

Depends on the density. If you're talking 60lb density, closed cell, a chainsaw would be appropriate.

However, 2lb closed cell, probably the claw end of a hammer/ a big flat-head screwdriver, and a drill with a wire brush attachment. (The wire brush is very easy on plumbing lines..the hammer, well, be carefull!)

1/2 density open cell, your hands could just scoop it out.

What make is the hot tub?

It's a 1992 Coleman Horizon 400. The system shut off during the VERY cold winter and now I have leak(s). I know where one of the leaks is and it is in one of the flex PVC pipes. I have to dig quite a bit to get at it and given the age of the tub and the possibility that there may be more leaks, I am considering digging it all out and re-running all new pipe. Given that the system turned itself off and appears to be flaky, I will probably also be replacing the system board and heater.

Thanks for the suggestion. The hammer claw is something I never thought of. Given your description, it appears I have the 2 lb closed cell. It looks like yellow styrofoam.