Has anyone made a grid of PVC pipe or something similar that would be dual purpose as a grid for a square foot garden and as an irrigation system?
Go for it. What made you think of a grid? Usually planners use coverage of the heads or soil plume pattern in conjunction with available pressure and flow rate as the designing factor. There is nothing to limit you from do it except cost concerns. JMHO Aloha
Square foot gardens have a grid that divides a bed into 1 ft squares for planting. The beds seem really busy if I put a grid and a drip line in them. What about combining them?
It can be done but it is the expensive way to go. It is your money though. Are you talking about drip-tape across the squares or placing micro-drip lines with drippers in each square with a grid pattern of crossing mainlines? Tell us the flow rate of the T-tape drip line per foot or per dripper? Aloha
I have seen exactly what you are asking about!
Here is a link that might be useful: SFG Supply