I agree with Don. My experience with bell siphons is that you have to periodically tweek/adjust them. I now have constant flow and there is really no maintenance. Just replace the bell siphon standpipe with a smaller pipe set to the height that you want to keep the water in the GB. This offers the advantage that you can raise your water level when starting seedlings if your GB is very deep, and then drop it as the roots start to grow. Otherwise, if you have good wicking media and not too deep a bed, the capillary action will usually get moisture up to where you need it.

Don,

If you have thoughts of preferring a continual flow setup, you can readily convert...