Concrete block wall with drain?

Rebuilding the wall is easier than cutting a drain channel? You can rent a gas powered saw. If you want to rebuild the wall, you could pour concrete about 4" high above the patio with PVC drain pipe set in it and then use block from there on up. Or just make holes in the existing wall for drain pipe. Me, I'd rent the saw.

I used a garage door threshold seal and some liquid nails.  Mike Holmes would tear out the slab and pour a new one.

There is if you build it that way.

That is the puzzle. I could remove the concrete block wall, install a series of drains, cover the drains with styrofoam blanks and then pour a new concrete wall which would then have pockets for the drains.

Go for it ! Don't let us stop you - after all you were looking for the "easiest solution " ... duh. John T.

If the wall is otherwise OK, why would you do all that instead of renting a concrete saw and cutting off the end of the patio where it meets the wall? It's one cut with the saw, no? And HD and similar have troughs and grate covers that fit 4" pipe.

What's on the other side of this wall? Where's the water going to end up going?

If it's just a block wall unless they infilled it, you can just poke the drains through it.

Certainly w/o seeing the situation it's difficult to say anything truly definitive...post some pics somewhere...

Yes, also unknown is how much water? If it's just 1/2" that's left after a rain, just drilling some holes to give it a way out might be enough.

They make a fart fan vent cover for 3" and 4" ducts that just have small fixed louvers. (Metal or plastic)