I am having problems with my auto siphons. I am thinking I don't understand exactly how they work. My GB are about 1 meter wide, 2.25 meters long and 230 mm deep. The water is distributed into the GB from a tee bar at one end. It has 5mm holes every 25mm along the bar. My auto siphon is centered at the opposite end of the GB. I have a 25mm stand pipe with a small hole (3mm) drilled into it at the bottom. It is 30mm shorter than the GB depth. The bulkhead is 25mm reduced to 20mm back to 25mm PVC pee trap then dumping back into the tank within 300mm of the bulkhead. The bell is a 70mm ABS pipe with cut outs around the bottom. I used a 40mm hole cutter and cut 6 holes around the pipe, then cut it in half to make two bells. The bell is 220mm high, sealed with an end cap at the top. I used a drip tee fitting mounted into the top of the side 25mm from the top, then a piece of 5mm pipe 170mm attached to the side of the bell. The bell is surrounded by a 100mm ABS pipe with a couple hundred 3mm holes to allow the water in around the bell. My pumping system fills the GB in about 15 minutes. The system was filling, starting the siphon then stopping about 1/4 the way down. I thought the gravel wasn't letting the water drain to the siphon fast enough so I added a half round ABS drain pipe down the middle of the bottom of the GB. It has about 1000 3mm holes in it. That didn't help. Then I discovered my air vent pipe, which I had cemented in with epoxy, leaked. I fixed that, but then the GB filled without the siphon starting at all. I then cut out the end cap and replaced it with a plexiglas window. Now I can see the the level inside the bell does not fill as fast as the GB. Am I filling the GB too fast? Is my stand pipe too tall? I would appreciate any and all advice you could provide. Thanks in advance, Grant