Abstract: The invention addresses the problem of preventing a buildup of water conditioning chemicals in a swimming pool water circulation system in the event of a circulation system failure. The invention involves providing a control for the chemical regulation system which is responsive to the water pressure in the circulation system and determinative of the output of the chemical pumps of the chemical regulation system as a function of the pressure of water in the circulation system. The chemical injection pumps may be disabled when circulation pressure falls below a predetermined threshold, whether caused by power failure, mechanical pump failure, or obstruction of the intake pipe. Related apparatus, systems and methods are disclosed.