Part # CH100; For permanent installation in return line on the pressure side of the pump, downstream of all equipment, in new or existing pools or spas. Standard with 2-inch slip PVC fittings and adapters for 1½ inch. External fine control valve adjusts the feed rate to meet specific pool or spa needs. Top-load large or small Trichlor or Bromine slow-dissolving tablets enables an effective, trouble-free way to sanitize pool or spa.