Rainbow's commercial 300-29X series of offline chlorinators are designed for large pools or pools with high chlorine demands. Works on the pressure side of the pump and is used with slow dissolving Trichlor tabs and sticks or bromine tabs and sticks. Holds approximately 3 times more than the 300 and will dispense 5 times the chlorine or bromine. Includes a heavy-duty 1/2 in. control valve and a replaceable 1/2 in. check valve.