The patio looks like in the picture. I have no idea if this is standard practice but it looks dumb to me. There is a very small space between blocks and that is filled with dirt. Virtually the patio holds the water in heavy rain when the runn off water should go over the edge of a graded patio. I am wondering what would be the best way to improve the situation. I am thinking about drilling holes like below, one per block. I have no idea how easy it is. The other option would be to enlarge the spaces between the blocks.
The cement blocks are beveled, the maximum diameter of a hole can be 0.5"
Best Answer
One easy solution is to rent a grinder, and a diamond blade, and cut (from the top) channels into the slab (where your drill holes are positioned). then you can insert your runoff pipes and then fill the holes with fresh cement.
Unfortunately, I don't see any practical way to drill at the angles which you propose, you will have to remove paving and create space to drill at those angles.