Reverse osmosis systems require adequate water pressure to function correctly. Insufficient pressure reduces water production rate, decreases PFAS rejection efficiency, and in some cases can prevent the system from producing treated water altogether. Understanding pressure requirements is essential for installation planning and troubleshooting.
Minimum Pressure Requirements
Most residential RO systems require a minimum inlet pressure of 40 to 60 psi to operate effectively. Standard municipal water pressure typically falls between 40 and 80 psi, placing most homes within the acceptable range. Well water systems and homes with pressure regulators set low may fall below the minimum, requiring a booster pump to enable adequate RO operation.
How Low Pressure Affects PFAS Rejection
RO membrane rejection of contaminants including PFAS improves with higher net driving pressure. At very low pressures, the osmotic pressure opposing flow is a larger fraction of the driving force, reducing effective rejection. Studies of RO PFAS rejection under varied pressure conditions show measurably lower rejection rates when operating near minimum pressure thresholds. Installing a pressure booster pump when inlet pressure is below 50 psi is recommended for optimal PFAS removal performance.
Pressure Testing and Adjustment
Testing your cold water supply pressure with an inexpensive pressure gauge before installation identifies whether a booster pump is needed. Many RO systems include a low-pressure shut-off valve that prevents the system from producing water when pressure falls below a threshold — useful for preventing low-quality output when pressure temporarily drops, but a diagnostic signal worth investigating if the system shuts off frequently.