Nearly 24" to the just off the floor. I call them poop suckers as they remove everything off the bare floor. I like these vertical pipes so well, that I had eleven holes drilled on the top of the big tank to accommodate my mechanical filtration.
My pipes will be the only "decoration" in my undecorated tank.
Since I made these pipes for the big tank system, we had to jury rig the plumbing in the small tank when the fish broke another bulkhead. We just ran a pipe straight down through the hole without using bulkhead. It actually works better with no chance of breaking any bulkheads. I am actually going to redo two of these pipes, as we have no need from drawing water from near the top of the tank. I'm going to just run the PVC pipe down without a bulkhead. Drawing water from the bottom of the tank has a lot of advantages. It makes draining the tank a breeze (we just open a valve)--we do have to pay attention or we could drain the tank dry which I accidentally did one time when I got distracted with a phone call.
I do have two 4' external overflow boxes on the tank which I am going to use for redundant filtration. Again, I am so against drilling sides/backs of tanks, I am going to run a vertical pipe to just off the bottom of the sump to return the water to the main tank.