For many years, PRIMUS has strongly and repeatedly advocated for the installation of a reverse osmosis system to provide pure water to PRIMUS integral and standalone boilers.

Impure feedwater is the root cause of a host of easily avoidable sterilizer downtime issues, including fouling of steam valves, chamber discoloration, and check valve failures.

While purchasing the reverse osmosis system (Option P30) when ordering a PRIMUS sterilizer is easier and more cost-effective, it is relatively simple and inexpensive to install a reverse osmosis system in the field.

Introducing PRI-Pure Reverse Osmosis System from PRIMUS Sterilizer

A field installation should only take 2 – 3 hours if accomplished by a PRIMUS Authorized Service Agent (ASA) or an experienced in-house technician who has completed the PRIMUS Steam Sterilizer School.

The information below outlines the basic steps required to accomplish an aftermarket installation. PRIMUS service associates can also help via phone or e-mail if unexpected issues arise.

Preparing the Sterilizer for the New Reverse Osmosis (PRI-Pure) System

  1. Turn off all power and water to the sterilizer.
  2. Follow all facility lockout/tag-out requirements.
  3. Disconnect city water to the boiler.
  4. Remove the feed water pump and motor.

Installing the New R/O System

  • The R/O filter system is usually mounted on the back of the sterilizer but can be mounted on the side if there is sufficient room. Some end users also prefer mounting the system on an adjacent wall
  • The water tank for the R/O system should be mounted just below the filter system. This tank holds approximately 10 gallons
  • Place the new pump and motor in the same place as the pump that was removed

The original pump and motor are a two-piece design.

The R/O System pump and motor is a one-piece design

  • Connect city water to the incoming port of the R/O system
  • Connect the R/O water from the filter to the top side port of the water tank
  • Connect the R/O wastewater to the floor drain
  • Connect the bottom port of the water tank to the boiler feed pump
  • Connect the feed pump to the boiler feed water solenoid
  • Connect the tank overflow to the floor drain
  • Note that the R/O tank has two floats:
    • The top float is mechanical and shuts off the flow of R/O water when the tank is full
    • The bottom float is electronic and removes power to the boiler contacts if the tank runs low on R/O water
    • The R/O low-water float connects in series with the boiler low-water cut-off (LWCO) probe to prevent the pump from running dry for an extended period of time (see the included boiler electrical drawing for the proper wiring configuration)

Returning the Sterilizer and Boiler to Service

  • Turn on the water to the R/O system
  • The R/O system for PRIMUS vertical door sterilizers produces approximately 100 gallons every 24 hours
  • The RO system operates best at 70 to 80 PSIG water pressure but will work with water pressure as low as 40 PSIG. At 40 PSIG, the output is about half that at 70 PSIG
  • Once the tank is full, turn On the sterilizer and the boiler
  • The boiler should be blown down to remove residual sludge from operating on untreated facility water. Additionally, boiler elements with hard scale should be thoroughly cleaned or replaced
  • The sterilizer can now be returned to service

More Information

Water quality: Why is it so important in a sterilizer?

Steam quality

PRIMUS water quality testing laboratory

Does my water have to be pure?

Have a question, or having difficulties? Talk to Dave Schall, our PRIMUS sterilizer expert, who is here to assist you anytime at 877.679.7800 extension 1212 or email at

Visit us at

Back to Blog