Bricks, Masonry, Asphalt and Concrete - copper pipe in masonry wall

My house is made of cinderblock and concrete. I need hot water in my utility room.

I want to run 1/2 copper pipe from under my kitchen sink, thru the wall to the outside, along the outside wall to the back of the utility room, and thru the wall again. The outside run is about 18 feet long.

A friend told me that I can use a circular saw with a masonry blade to cut a trench for the outside run. Then lay the pipe in the trench, and refill the trench.

Does this sound feasible? What size saw do I need? Any special masonry blade? What should I use to refill the trench: concrete, mortar?

So, I think I know how to do this, I just don't know the specifics. If I could get some assurance, before getting started, that I won't ruin my saw, or (worse) my house, that would be greatly appreciated.

Geo.

18 feet with a circular saw? Not me. You'll be there all day, maybe longer.
I would rent one of ----> Partner K950 Gas Ring Saw THE WORLD?S FIRST 14 GAS-POWERED CUTTER WITH A 10" CUTTING DEPTH (968307101), Cut Off Saws - Toolfetch.com (http://www.toolfetch.com/p-k950.shtml) if I were going to do it at all.
BUT
Is it necessary to run the pipe outside and if it is can you use PVC or Pex instead?

Wow, helluva saw! Can't run the pipe inside, too much stuff in the way (two inside walls, cabinetry, shower stall, etc). So it will go outside. Copper was my choice, simply cause all the pipe in the the house is copper, but I guess it doesn't have to be. Do you mean to lay the PVC in the concrete? Or just leave it exposed and attached to the wall?

Now that I see you're in the caribbean, I guess you don't have to worry about freezing, so you can leave it explosed.

Well, I know I can leave it exposed and that would be the easy route. It would also be the least aesthetic for when we sell the house.

I think I'll go back to original plan, which, with the help of these forums, has been refined a little.....
a) rent concrete saw to cut trench,
b) cut copper pipe,
c) wrap pipe in insulation for expansion/contraction,
d) lay pipe in trench,
e) re-pack trench,
f) re-paint.

A couple of more tweaks should do it -- What should I re-pack with? concrete? morter? And is there any kind of reinforcement I should use when re-packing?

I guess I would use Portand cement mixed with sand. 3 sand to 2 portland would be good. I don't know what you painting though.