If you run a café, a commercial kitchen, a hotel bar or an office in Britain, someone has probably told you that you "need RO". So what is reverse osmosis, and does your site really need it? Reverse osmosis is a treatment process that pushes water through a very fine membrane under pressure, leaving most dissolved minerals and salts behind. It is excellent at a few specific jobs and unnecessary for many others. This guide explains how it works, what it takes out, what it needs in upkeep, and how to tell whether a softener or a simple carbon filter would do instead.
TL;DR
- Reverse osmosis (RO) strips out most dissolved solids, including the calcium and magnesium that cause scale.
- UK mains water is already regulated for drinking. RO is about equipment protection, consistency and specific process needs, not making tap water "safe".
- If your inlet water is very hard, it needs a softener before the RO, otherwise the membrane will block sooner.
- RO water is very low in minerals, so we either blend it with filtered inlet water at installation or fit a remineralisation cartridge to reach a target range.
- In UK regions with low hardness, an RO membrane typically lasts 1 to 3 years.
Not sure which route fits your site? Talk to Our Team with your postcode, equipment list and daily water use.
In this article
- How reverse osmosis works, step by step
- What is reverse osmosis water, and what does RO remove?
- Where RO earns its place in a UK business
- When you probably do not need RO
- Drainage and installation
- Membrane life and remineralisation
- Choosing a system
- Frequently asked questions
- Sources
How reverse osmosis works, step by step
Osmosis is the natural movement of water across a membrane from a weaker solution to a stronger one. Reverse osmosis turns that round. A pump raises the pressure on the incoming side so water is forced the "wrong" way, from the mineral-rich side to the clean side. The membrane lets water molecules through and holds most dissolved substances back. Those substances are flushed away in a separate stream, usually called reject or concentrate.
A commercial unit is never just a membrane. A typical layout in a UK back-of-house looks like this:
- Softener, where the water is very hard. Hardness minerals scale the membrane surface, so in hard-water areas the supply is softened first to stop the membrane blocking early.
- Sediment pre-filter. Catches grit and rust so the membrane does not clog.
- Carbon pre-filter. Takes out chlorine and chloramine. This matters because the disinfectant UK water companies use to keep mains water safe can damage common thin-film membranes over time.
- Pump and membrane. Where the actual separation happens.
- Blending or remineralisation. Sets the final mineral level of the water.
- Controls. Flow and quality readouts, filter-change alarms and leak protection on better units.
What is reverse osmosis water, and what does RO remove?
Reverse osmosis water, often shortened to RO water, is the "permeate" that comes out of the clean side of the membrane. It is very low in total dissolved solids (TDS). If you want the background on how TDS is measured and what the readings mean, our guide to TDS and ppm explained covers it.
In practice, RO removes most dissolved salts and minerals, including the calcium and magnesium that cause limescale. How well it performs at your site depends on the membrane, the pressure, the water temperature and how well the unit is maintained. A membrane that is overdue for replacement does not perform like a new one.
Two UK points are worth knowing:
- Hardness is not a safety issue in UK law. The Drinking Water Inspectorate (DWI) states that the UK drinking water regulations do not set standards for hardness, calcium or magnesium. Hard water is a scale problem for your kettles, boilers and steam ovens, not a compliance problem.
- PFAS is on the radar. The DWI applies a guideline value of 0.1 micrograms per litre for the sum of 48 named PFAS compounds, and your water company monitors against it. If PFAS is a concern for you, start with your supplier's published results for your area.
Where RO earns its place in a UK business
RO is the right tool when you need water that is consistently low in minerals, whatever arrives from the mains that week. Common UK examples:
| Site | Why RO helps | What to watch |
|---|---|---|
| Speciality coffee bar | Lets you set a repeatable mineral recipe for extraction and protects boilers from scale | Needs blending or remineralisation, as pure permeate makes flat coffee |
| Combi and steam ovens | Stops scale on steam generators, which is a common cause of callouts | Check the oven maker's water spec and warranty conditions |
| Ice machines | Clearer ice and less scale on evaporator plates | Size for peak summer demand |
| Glasswashers in bars | Spotless glasses without hand polishing | Often paired with a softener upstream |
| Labs and small production | Consistent low-TDS feed water | Some processes need validated water grades beyond a standard RO unit |
The reason is simple. In a hard-water area a steam oven or espresso boiler can scale up quickly, and a softener alone does not lower TDS. Your water company publishes the hardness for your postcode. For the coffee side, our article on how RO water changes coffee quality goes deeper.
Our range of reverse osmosis systems runs from a 60 litre per hour unit for a single coffee bar up to engineered industrial plants. Three that suit most hospitality and office sites:
Want a second opinion on sizing? Request a Quote and tell us your peak hourly demand and which machines the water feeds.
When you probably do not need RO
RO is not a default upgrade. It adds a pump, a drain connection and a membrane to replace. Skip it, or at least start elsewhere, if:
- Your only complaint is limescale throughout the building. A commercial water softener treats every outlet and costs less to run. Check with your coffee machine maker whether it accepts softened water.
- The issue is taste or chlorine smell at a drinking point. A carbon filter handles that at a fraction of the cost.
- You run a small office with a water dispenser. A filtered mains-fed dispenser is usually enough. RO only makes sense if you specifically want low-mineral water.
A useful rule: decide what problem you are solving first, then pick the treatment. Our guide to filtration versus treatment walks through that thinking.
Drainage and installation
Every RO system produces two streams: the clean water you keep and the reject water that carries away what the membrane stopped. That means every unit needs a drain connection close by. Points to plan for:
- A drain point near the unit, and a route for the drain line.
- A flood alarm and automatic shut-off.
- A softener ahead of the RO if your water is very hard.
- Fittings and installation that comply with the WRAS water fittings rules.
Membrane life and remineralisation
How long a membrane lasts depends on your inlet water. Scale, organic fouling and chlorine damage all reduce output. In UK regions with low hardness, membranes typically last 1 to 3 years. In hard-water areas, soften the supply first, or scale will block the membrane sooner. Pre-filters need changing on time too. Our article on RO membrane maintenance explains the warning signs, such as falling flow or rising TDS on the readout.
Setting the final water. Permeate is so low in minerals that it can taste flat and does not suit every machine. There are two ways we set the final water:
- Blending. During installation our team blends the RO water with filtered inlet water, adjusting the mix to reach your target characteristics.
- Remineralisation cartridge. We supply a cartridge that brings the output into a target remineralised range.
Our maintenance plans cover scheduled filter and membrane changes, so you do not rely on someone remembering.
Choosing a system: a short checklist
Before you request prices, gather:
- Your water supplier's hardness figure for your postcode (or your own test results).
- A list of equipment the RO will feed, with each maker's water specification.
- Peak demand in litres per hour, not just daily totals.
- Available space, power and a nearby drain.
- Who will change filters and membranes, and how often.
Frequently asked questions
What is reverse osmosis in simple terms?
It is a way of cleaning water by pushing it through a very fine membrane under pressure. Water passes through, while most dissolved minerals and salts are held back and flushed away.
What is reverse osmosis water used for in business?
Mostly coffee, steam ovens, ice machines, glasswashers and some production processes, where low and consistent mineral levels protect equipment and give repeatable results.
Is RO better than a water softener?
They do different jobs. A softener stops scale across a building. RO lowers almost all dissolved solids at one point of use. In hard-water areas the two work together, with the softener protecting the RO membrane.
Does a reverse osmosis system need a drain?
Yes. Some water always goes to drain carrying what the membrane removed, so the unit needs a drain point nearby.
How often does an RO membrane need replacing?
It depends on your inlet water. In UK regions with low hardness, 1 to 3 years is typical. Very hard water shortens that unless it is softened first. A readout showing rising TDS or falling flow is the usual sign.
Talk to Our Team about reverse osmosis
If you are weighing up RO for a café, kitchen or office, send us your postcode, the equipment the water will feed and your busiest hour of demand. We will recommend whether RO, a softener or a simpler filter fits, and size it properly. Get in Touch.
Sources
- Drinking Water Inspectorate: water hardness
- Drinking Water Inspectorate: PFAS and forever chemicals
- WRAS: Water Regulations Advisory Scheme
- Sovereign Water product specifications: Noble RO 60, Imperial RO, Majestic RO