Water filtration and purification units and replacement cartridges and filters therefor; Water filters and components thereof, namely, filter cartridges for reduction of hard water, acid water, iron, lead, dirt, rust and sediment from drinking water supplies, hot water systems, and household appliances and humidifiers, for domestic and industrial use; Water sterilizers; Water softening apparatus; Water filtration systems comprised of a filter cartridge, tubing, connectors and brackets; Reverse osmosis water purification system