Abstract: A charging conduit extends from a source of grey water to a separate inlet of two tanks arranged in parallel. A discharging conduit extends from a separate outlet of each tank to the source of grey water for recycling the grey water. Upper and lower level-detectors are provided for each tank and a flow detector monitors the flow of grey water through the discharging conduit. Valves control the flow of grey water into and out of each tank and respond to the level of grey water in the tanks monitored by the level-detectors.

Abstract: An upstream conduit extends from a container containing reusable waste water to a junction and a downstream conduit extends from the junction to a destination for the waste water. There is a third conduit through which fresh water, under pressure, flows to the junction. The flow in the third conduit is controlled by a valve which is normally open but shuts when a flow switch in the downstream conduit detects the demand for the waste water at the destination. At that time the demand is satisfied by waste water from the container. However, should there be insufficient waste water in the container to satisfy the demand, a level switch in the container deactivates or overrides the operation of flow switch thereby causing the valve in the third conduit to open When the valve opens, fresh water from the third conduit satisfies the demand.

Abstract: A process of producing a plastic heat exchanger where a multiplicity of tubes are welded to tube headers having raised collars surrounding each of the tubes, using an infrared energy source such as a laser to melt-bond the tubes to the collars.