A pressure or float switch senses the storage tank conditions and starts or stops the system as needed. A few systems flush the membrane with treated water at shutdown to reduce mineral deposits and extend the life of the membrane. RO systems should be monitored to ensure proper operation. A major problem with many home water treatment devices is that the user does not know if they are working. Reverse osmosis is easy to monitor with a conductivity or total dissolved solids meter.
Some systems have a built-in monitor, and portable meters are available.
When the meter reading increases, the operator knows that ions are getting past the membrane, and it is time to change the membrane. Pressure gauges, which are common with large units, allow the user to know when the filters and membrane are plugged and need cleaning or changing. Equipment Available Home RO units come in various sizes, styles and types. These units produce as little as a gallon to perhaps 20 gallons per day and the reject water usually flows down the drain. The storage is usually 1 to 3 gallons and may be a built-in pressure tank or a separate container.