The SSF/x slow sand filter for use in treating drinking water for homes or rural villages with features providing simpler on-site assembly, preset maximum flow, easy monitoring of pressure head loss, protection of piping, and a harrowing system for cleaning. The filter employs a novel hydraulic scheme which places most pipe and plumbing within the filter vessel. The filter employs a novel device that combines flow control, pressure measurement, freeze protection, and anti-siphon features. This in combination with a relatively shallow supernatant level provides for consistent reliable operation, easy maintenance, and reasonably long filter runs as deemed very desirable in remote rural locations.