Finally, four days later, I finished the project and we were back in business watering the lawn. The stainless cylinder in the foregroud is a centrifugal sand filter. For the time being I put a ball valve on the flush port so I can manually remove the sand. But, when/IF I ever get around to putting in a completely new and full-yard irrigation system, the ball valve will be replaced with a standard electric irrigation valve and it will flush itself via the controller.