Cartridge pre-filters installed ahead of a reverse osmosis unit serve what purpose?

• A. They remove dissolved minerals
• B. They remove suspended matter to protect the membrane
• C. They increase system pressure
• D. They are optional and have no effect on performance

Answer: (B)

The main idea is that cartridge pre-filters protect the reverse osmosis membrane by removing suspended solids before water reaches the membrane. These filters trap dirt, sediment, rust, and other tiny particles that would otherwise accumulate on the membrane surface, causing fouling, reducing permeate flow, and increasing energy use and maintenance. By filtering out this particulate matter, the RO system can operate more efficiently and the membrane life is extended.

This isn’t about removing dissolved minerals—that’s what the RO membrane itself does. It also doesn’t increase system pressure; a clogged pre-filter can actually cause a pressure drop. And they’re not optional if you want consistent performance—the pre-filter dramatically helps protect the membrane and maintain production.