You can also switch to Constant Flood and just not use siphons. This is an option that many people here use when they want to expand their systems and don't want to get a larger sump tank. Basically in CF the grow beds retain water if the power goes out (so there is no weep hole near the bottom of the standpipe). All you'd need to do is switch to a standpipe without a weep hole and remove the bell from over the standpipe. Water will just flow over the top of the standpipe so this sets the water depth in the grow beds. See "BYAP Trials" thread if you have questions about how well this works.
Just noticed that your plumbing is cast into the system
- you've got some leeway as far as the water depth (surface shouldn't stay wet, usually water is about 1.5 to 2 inches below the surface). If you cut the plumbing too short is there room to put a connector with a short length of pipe on the stub - I change the water level occasionally and this is how I do it (I occasionally like to seed the surface of a grow bed so I'll raise the water depth temporarily, to make the seeds stick to the moist media a bit higher up)