If it is the manual version, just open the flush valve for a few minutes every week or so while running water in as normal. While this is open, the pressure gauge on the RO, if you have a gauge, should drop to zero and zero (or close to it) "pure" water should be coming out, showing that no water is being pushed through the membrane thus all the water is passing rapidly "along" the outside membrane wall, flushing the trapped bad stuff out the waste water tube. When finished, just shut the valve and the pressure gauge should go back to it's normal reading and "pure" water should start to flow again. At least that's how mine works
HTH. JME.
