What to Look for When Buying an RO System

There are several items to consider when buying an RO system. Follow this guide so you are sure to select the right system for your facility.

Materials of Construction

Materials of construction (MOCs) are vitally important for a robust RO unit. Do not skimp on MOCs when buying an RO system.

  • Feed piping (feed to the high pressure pump) is often made out of PVC, but PVC can become brittle and crack easily. Caloris recommends using Schedule 10 304 stainless steel instead.
  • Permeate piping also is usually made out of PVC. Make sure it is Schedule 80 PVC.
  • Skids are often e-coated or painted steel, which can corrode in the event of any imperfection, leading to rust dripping on everything below. Caloris recommends bead-blasted 304 stainless steel instead.


When buying an RO system, be sure your new unit consists of top-of-the-line, readily-available parts to save headaches down the road.

  • The feed pump should be made out of all stainless steel wetted parts (NO iron).
  • Cartridge filter housings should meet ASME design standards.
  • Chemical pumps – it pays to invest in high-quality, robust dosing pumps. Losing anti-scalant or anti-oxidant injection can quickly ruin membrane elements.


  • Pressure transmitters are typically only feed and concentrate, but Caloris recommends having feed, intermediate and concentrate pressure transmitters for an indicator at individual stage. Fouling is best diagnosed by knowing which stage has a pressure drop.
  • Temperature transmitters — Caloris recommends a temperature transmitter prior to the membranes. High temperatures can quickly ruin the membranes.
  • Flow transmitters are usually in a paddlewheel configuration, which can bind easily. Caloris recommends feed and concentrate magmeter style, which have no moving parts instead.


Many membrane system suppliers do not include CIP.

  • The CIP process should be easily conducted, so that it gets implemented before a degradation of performance becomes excessive and recovery becomes more difficult.
  • Caloris recommends a system with a CIP tank and skidded CIP pump, sized 40 gpm per housing.
  • Valving is typically limited. Caloris recommends including valving to individually clean each RO stage.
  • Heating is typically not included. Caloris recommends CIP heating and controls, including a temperature transmitter for membrane high temperature protection.
  • CIP is most efficient at greater than 90 degrees F.

Energy Savings

  • Capture energy saving by using a variable frequency drive (VFD) for the feed pump — avoid using a feed throttling valve for feed pump control.
  • Discuss energy savings with your system vendor. Depending on the quality required, the supplier may offer many membrane options for energy savings. The higher quality membranes usually pay for themselves within a year.

Plug & Play

RO systems often arrive ready to install. Make sure that your new RO system will include:

  • Your new unit should arrive fully tested
  • Single 120V connection
  • Single 3-phase 460V connection
  • VFDs and MCCs not supplied loose
  • VFDs configured and tested before commissioning
  • Single 80 psig instrument air connection
  • Instrumentation configured and tested prior to shipping
  • Automated valves tested prior to shipping
  • Piping pressure tested prior to shipping


Your vendor should offer the following:

  • Commissioning services and operator training
  • Commitment to you doesn’t end at end of commissioning: follow-up training and support as needed
  • Pretreatment chemicals, cartridge filter and membrane replacement services
  • High level of communication for at least 2-3 months after commissioning

A Better Process

At Caloris, we offer all of the above and more on all of our RO membrane filtration systems. Contact us today to discuss your filtration needs. Call 410-822-6900 or send email to problem.solved@caloris.com to be connected to a membrane system specialist.


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About Caloris

Caloris transforms process systems design for the better with unexpected, future-focused solutions that solve real operational problems. We engineer efficient, dependable and productive solutions that also improve environmental sustainability where practical. Designed with the end user in mind to drive plant productivity. Caloris offers evaporation, membrane filtration and spray drying process systems for food and dairy industries, as well as for water reuse and wastewater treatment applications. Both Caloris’ custom and pre-engineered packaged systems are designed to meet our customers’ specific concentration/purification needs utilizing the most cost effective and energy efficient technologies available. Whether concentrating dairy, food or juice products at a high-volume production facility, or processing industrial wastewaters to reduce transportation and treatment costs and recover re-usable water, Caloris provides a range of options and technologies.