An R.O. machine works best when it‘s running clean water through it. Otherwise, the membranes let nature take over. Then you have not reverse osmosis but osmosis. It’s better to have a small machine running twenty-four hours a day than a big machine running two hours and then shutting off. R.O. membranes should have a constant positive flow through them. Some industry leaders believe twelve to thirteen hours is the maximum you should run an R.O. unit a day. They think the machine will last longer.

Silica, iron, aluminum and bacteria cause irreversible damage to membranes and that’s why pre-filters are a must to keep membranes from fouling. Fouling results when particles suspended in the feed water are deposited within the R.O. unit. Fouling reduces permeate flow rate. Bacteria fouling usually doesn’t cause the permeate conductivity to increase until your system is extremely plugged. Other particles may cause permeate conductivity to increase.

Most biological and particulate silica foulants can be removed with the proper chemicals. Bio-fouling is a problem. Pre-treatment may have little impact on R.O. unit fouling. Simply killing the bacteria won’t work because the same number of fouling particles (living or dead) still enter the R.O. unit. The best way to handle bio-fouling is cleaning the equipment and the upstream pipes and filters. Chlorinated water will be bad and should be un-chlorinated before entering the R.O. unit. Fouling by non-living particles is handled by your pre-filters, or additional sediment filters or cartridge filters with a nominal filtration rating of five microns or less. This can be complicated stuff and you can call your franchsior for a telephone number of a fair and honest local or regional water purification consultant.