Plumbing an Earthan Bed is relatively simple. You have an inlet which you can control the inflow with a valve and an outlet which you can control the depth of water with a stand pipe. No different to plumbing a constant flow gravel bed in aquaponics.
The premise of an Earthan Bed is to incorporate soil into an integrated aquaculture system (aquaponics). Using good quality soil avoids many of the nutrient deficiencies associated with aquaponics. Using soil you will avoid nutrient deficiencies seen in inert media like sand, Perlite,Rockwool, Expanded Clay Aggregate and Vermiculite. For the larger commercial grower, easier entry to organic certification, but not without risk.