RBM's Rinox family covers four adjustable pressure reducing valves, all from G1/2" to G2", all rated to 80°C. On a quote sheet they look interchangeable. They aren't: the adjustment ranges, internal design, certification and even the thread gender differ, and those differences decide which one belongs on the job.
The four valves side by side
| Rinox Plus M (2581.A) | Rinox Plus Smart M (2581.B) | Rinox Due (87.B) | Rinox First HP (51.A) | |
|---|---|---|---|---|
| Operation | Diaphragm, compensated cartridge | Diaphragm, compensated cartridge | Compensated piston, single SS seat | Diaphragm, compensated, double SS seat |
| Outlet adjustment | 80–700 kPa (preset 500) | 80–700 kPa (preset 500) | 50–700 kPa | 600–1,000 kPa |
| Nominal pressure | 25 bar cold / 16 bar hot | 25 bar cold / 16 bar hot | 25 bar | 40 bar (max inlet 25 bar) |
| Body | Anti-dezincification (CR) brass | Anti-dezincification (CR) brass | Nickel brass | Nickel brass |
| Built-in filter | 800 micron, removable cartridge | 800 micron, removable cartridge | — | — |
| Connections | Female x female | Male x male | Female x female | Female x female |
| WaterMark | Lic. 26790 | Lic. 26790 | Not listed | Not listed |
| Price (1/2" / 3/4") | $105.59 / $105.59 | $200.00 / $222.00 | $142.00 / $142.00 | $362.00 / $379.00 |
All four have a F1/4" gauge port and ISO 228 parallel threads.
Rinox Plus M — the default for drinking water services
The Rinox Plus M is the one to reach for on a standard residential or commercial cold water service. It's WaterMark licensed, comes preset at 500 kPa, and its compensated seat means the outlet setting holds steady as mains pressure moves around. The internal cartridge and 800 micron filter can be pulled for inspection and cleaning without removing the valve body from the line — the most common PRV service call is a dirty filter or seat, so that matters over the life of the install.
Rinox Plus Smart M — same valve, set without a gauge
The Smart M is the Plus M with a graduated calibration knob, so you can dial the outlet pressure without a gauge or tools. Handy for maintenance staff on commercial sites who need to adjust pressure without a plumber's gauge kit. Watch the connections: the Smart M is male x male, where the Plus M is female x female. Swapping one for the other on an existing line means changing the fittings either side.
Rinox Due — simple piston valve
The Rinox Due is a straightforward compensated-piston valve with a stainless steel seat, the widest low-end adjustment (down to 50 kPa) and a lower price in the larger sizes. Its listing describes it for general water conveyance and does not show a WaterMark licence, so check its certification before installing it on a drinking water service in Australia. It suits process water, irrigation and other non-potable lines well.
Rinox First HP — first-stage reduction from high pressure
The Rinox First HP is a different tool. Its outlet range starts at 600 kPa, so it isn't designed to deliver a final 500 kPa service on its own. It's built to take high inlet pressure (up to 25 bar) down in a first stage, with a double stainless seat and an anti-water-hammer function. Like the Due, its listing doesn't show a WaterMark licence — check certification for potable use.
When to use two-stage reduction
Every PRV has a practical limit on how far it should drop pressure in one step. Ask one valve to take very high inlet pressure all the way down and you get noise, wear on the seat and a less stable outlet. RBM's guidance is to use the First HP where upstream pressures approach 25 bar. A typical arrangement is:
- Stage 1: Rinox First HP drops the high inlet pressure to somewhere in its 600–1,000 kPa range.
- Stage 2: A Rinox Plus M downstream takes it to the final service pressure (preset 500 kPa).
Fit gauges on both valves' F1/4" ports during commissioning so you can see each stage working.
Sizing: don't just match the pipe
A PRV sized to the pipe isn't always sized to the flow. Oversized PRVs running at very low flow can hunt and chatter; undersized ones drop too much pressure at peak demand. Check the manufacturer's flow charts against the job's peak flow before ordering the larger sizes (G1" to G2" step up significantly in price across the range).
Installation tips
- Install with isolation valves either side so the valve or cartridge can be serviced. Our press ball valve guide covers union valves, which make removal easier.
- Flush the line before fitting so construction debris doesn't end up in the filter or seat.
- Respect the arrow on the body and leave access to the gauge port and adjustment cap.
- Hot water use is fine up to 80°C, but note the Plus M and Smart M nominal pressure drops to 16 bar on hot water.
Browse the full RBM range, including ActivFlo water conditioners and T08/T55 tempering and thermostatic mixing valves, or the wider pressure reduction valves collection. For a compact 20mm boundary option, see our piece on the AVG PRVB20-BV20 combination valve.
Frequently Asked Questions
Which RBM Rinox PRV is WaterMark licensed?
The Rinox Plus M (2581.A) and Rinox Plus Smart M (2581.B) list WaterMark licence 26790. The Rinox Due and Rinox First HP listings don't show a WaterMark licence, so check certification before using them on drinking water.
What is the difference between the Rinox Plus M and the Smart M?
The Smart M adds a graduated calibration knob, so outlet pressure can be set without a gauge or tools. It also has male x male connections, while the Plus M is female x female.
When do I need the Rinox First HP?
For first-stage reduction from high inlet pressures (RBM recommends it where upstream pressure approaches 25 bar). Its outlet range is 600–1,000 kPa, so follow it with a second valve such as the Plus M for the final service pressure.
Can the Rinox Plus M be serviced without removing it from the line?
Yes. It has an inspectionable internal cartridge with an 800 micron filter that can be removed for cleaning or replacement while the valve body stays in place.