I would like to setup a subsurface irrigation system for my garden. I have several beds which, while I made each one perfectly level, are at different elevations (about 1 or 2 feet between each) . The source of the water will be a permanently mounted bucket, barrel or cistern of some kind, with a single valve to open to feed the system. I will have garden hose that goes from the cistern to the various beds in the garden. One inch below the surface of each bed will be a perfectly level PVC tube, with holes drilled in the top. The water source hose will go into one end of these tubes, and the other end will either be capped, or lead to a lower bed. Water will push out of the top holes to water the beds. QUESTION: Is there a simple way for me to ensure that the amount of water delivered to each bed will be the same? If I just run a hose to each bed, the beds at a lower elevation will get more water per minute than the higher beds, (due to greater water pressure at the holes in the tube), which I would like to avoid. Or, is this incorrect? Ideally I could let a higher bed’s PVC pipe feed a lower bed’s PVC pipe, so I don’t need to run a hose to EVERY bed, just every ROW of beds using a "mainline". More info: Other than my well pump, which is used to get water into the cistern, everything else is gravity fed. The bottom of the cistern will be about a foot above the highest bed. My thoughts so far: Could this be done by simply making the LAST hole in a bed’s PVC pipe larger, and use that to feed the next tube? If each bed has N holes, of radius R, how large would that last hole have to be to ensure the water that flows out of it is equal to the water flowing out of all the previous holes in the pipe? To complicate it, what if I have 2 or 3 beds below the first? Also, would a change in the water source pressure, as it drains, throw this hole-size ratio off? I am hoping to get an answer as simple/brilliant as: "drill holes" in this section of pipe, to let air in, or something like that.