SEWAGE DEPARTMENT TRAINING PROGRAM
How to Build a Free Access Gravity Sandfilter
Install the tank lid. The tank lid may be of metal, exterior plywood, or other durable material that would allow the owner easy access to the tank. Do not use concrete lids as the weight would be too heavy for access without power machinery.) Because of the cold winters, it is recommended that the lid be insulated by attaching foam insulation to the underside.
