You are generally safe if you stay between these numbers and have good pretreatment. If the membrane plugs prematurely the prefilter, not the membrane, may be to blame. If you are using TLC membranes, you need to use a carbon prefilter to remove oxidizing agents, even on nonchlorinated well water. Therefore, always use a carbon prefilter and use one that lasts. Again, the cost of a carbon filter is much lower than a TLC membrane element, so it pays to include a carbon filter.
Most systems also use a carbon filter downstream right before the tap.
Larger organics tend to foul the surface of the carbon media, allowing the smaller, often more harmful organics to pass. The RO membrane will reject the larger organic chemicals and other fouling contaminants, allowing the postcarbon filter to effectively remove the remaining, smaller organic contaminants by adsorption. On feedwaters with organics suspected of being carcinogenic or otherwise harmful, the post-carbon filter is crucial to meeting the consumer's needs and should always be included in the design. The importance of the storage tank is often overlooked, but it is vital to the proper design of the RO system. Lower quality water is produced and a higher percentage of water goes to drain.