A hotel, leisure centre, care home or busy commercial kitchen cannot run its softener like a café does. Before you choose a duplex water softener, a twin alternating set or one large single unit, you need to know three things: how much soft water the site uses in a day, how fast it draws it at peak, and whether it can ever go without soft water while the softener regenerates. This guide walks through the bigger Regal models, the Regal 500, Regal 750, Regal Twin 3672 and Regal Duplex 3072, and shows which question each one answers.
TL;DR
- A single softener stops softening while it regenerates. If your site can schedule that for the small hours, a single Regal 500 or 750 is often enough.
- A twin alternating set, such as the Regal Twin 3672, keeps one vessel in service while the other regenerates, so soft water never stops.
- A duplex water softener, such as the Regal Duplex 3072, runs both vessels at once to carry a higher peak flow.
- Compare flow figures on the same basis. The Regal 500's headline figure is a valve flow at a 1 bar pressure drop, not an operating rating.
- Check plant room height, floor loading and drain size early. The large twin sets weigh hundreds of kilograms and connect well above head height.
Planning a bigger site? Talk to Our Team with your hardness figure, daily use and peak flow.
Contents
- Single, twin or duplex: the core choice
- The four Regal models at a glance
- How to size a duplex water softener or twin set
- A worked example: a 120-bed hotel
- Plant room checks before you order
- Questions to ask any supplier
- FAQs
Single, twin or duplex: the core choice
Every ion exchange softener has to rinse its resin with brine from time to time. That rinse is regeneration, and during it a single-vessel unit cannot soften. Our Twin 3672 datasheet puts it plainly: hard water bypasses to service while a single softener regenerates.
For many sites that does not matter. A metered valve can delay regeneration until a quiet hour, so the bypass happens when nobody is drawing water. An office block, a school kitchen or a restaurant that closes at night usually fits this pattern.
It matters a great deal for sites that never stop. A hotel laundry running overnight, a hospital, a care home or a production line that runs in shifts will draw hard water every time the softener regenerates. A twin alternating set solves that by holding a second vessel in reserve.
A duplex set solves a different problem. It splits the flow across two vessels running in parallel, so the set can carry more water at peak than one vessel could. The Duplex 3072 datasheet frames it as double the flow for peak demand, and notes that the same vessels can be built as a twin set where uninterrupted supply matters more.
The four Regal models at a glance
These figures come from our current datasheets and match the live product pages.
| Model | Layout | Flow figure | Soft water between regenerations | Media | Brine tank |
|---|---|---|---|---|---|
| Regal 500 | Single vessel, separate brine tank | 6.12 m³/h at 1 bar drop | Not stated, depends on media chosen | Supplied empty: Ecomix or cation resin | 125 L |
| Regal 750 | Single bi-block | 3.5 m³/h operating, 4.3 m³/h maximum | 15 m³ | 75 L PC002 resin, loaded | 125 L |
| Regal Twin 3672 | Two vessels, alternating | 18.2 m³/h at 1 bar drop | Quoted to your water analysis | 700 to 725 L resin per vessel, quoted separately | 2 x 570 L |
| Regal Duplex 3072 | Two vessels, parallel | 15 m³/h duty (7.5 m³/h per vessel) | Quoted to your water analysis | 425 L resin per vessel, quoted separately | 2 x 570 L |
Two points stand out. First, the Regal 500 datasheet describes it as domestic and light commercial, while the Regal 750 datasheet lists hospitality, healthcare, estates and light industrial sites drawing 3 to 4 m³ an hour. Second, the 500's 6.12 m³/h is the flow its valve passes at a 1 bar pressure drop. It is not the same kind of number as the 750's 3.5 m³/h operating rating, so do not read the 500 as the faster unit.
Duplex builds are listed as an option on the Regal Twin 3672 page. The Duplex 3072 itself is quoted from its datasheet, so ask us for it by name. Not sure which layout suits you? Request a Quote and send us your site details.
How to size a duplex water softener or twin set
Work through these inputs in order. The first two are things you can find yourself.
Hardness. Your water company publishes a hardness figure for each postcode. Thames Water explains why much of its area is hard: rain soaks through chalk and limestone and picks up calcium and magnesium (Thames Water). Harder water fills the resin faster, which shortens the run between regenerations.
Daily soft water volume. Count only the outlets the softener feeds: calorifiers, boilers, laundry, kitchen equipment, showers if they are on the softened side. Meter readings over a busy week beat estimates.
Peak flow. Look at the worst ten minutes of the day, such as the morning shower peak in a hotel or a laundry filling several machines at once. The softener must pass that flow without too much pressure loss.
Hours of operation. If the site draws water around the clock, plan for twin alternating duty. If it has a reliable quiet window, a single unit with delayed regeneration may do.
Growth. The CE and Clack valves on these models can be linked. A Clack system controller can run 2 to 6 units in progressive flow, alternator, series or random mode, which leaves room to add capacity later.
A worked example: a 120-bed hotel
These numbers are an illustration only. Use your own meter readings.
- Softened side: hot water calorifiers, laundry and kitchen.
- Daily soft water use: about 18 m³ on a full night.
- Peak flow: about 4 m³/h during the morning shower rush.
- Operation: laundry runs until 2am and starts again at 6am.
A single Regal 750 rated at 15 m³ would need to regenerate more than once a day on this load, and each regeneration would leave the hotel on hard water for a spell. Its 4.3 m³/h maximum is also close to the peak. A twin alternating set gives the hotel soft water through every regeneration and far more flow headroom. The exact media volume, and so the run between regenerations, is quoted against the hotel's hardness.
A smaller guest house with 6 m³ a day and a quiet night-time window is a different story. A single Regal 750 set to regenerate at 3am may be all it needs.
Plant room checks before you order
The big sets are serious pieces of plant. Check these with your building manager before you commit.
- Height. The Twin 3672 connects at 2395 mm, give or take 30 mm, with the drain at 2540 mm. The Regal 750 stands 1585 mm tall.
- Weight. Dry weights are 100 kg for the 750, 220 kg for the Duplex 3072 and 280 kg for the Twin 3672. Media, water and salt add a lot more in service.
- Drain. The twin and duplex sets use 2 inch class connections and a large drain line, so the drain must take a backwash flow of up to 26.1 m³/h on the Twin 3672.
- Power. Each valve needs a 230 V supply. The Duplex 3072 accepts 100 to 240 V.
- Inlet limits. The 500, 750 and Twin 3672 accept water from 4 to 30 °C at 2 to 6 bar. The Duplex 3072 is rated from 4 to 43 °C at 1.4 to 8.6 bar.
- Feed water. The datasheets cap hardness at 750 mg/L as calcium carbonate and iron at 0.2 mg/L, with a 100 micron sediment prefilter ahead of the Regal 500.
Keep drinking water off the softened side. The Drinking Water Inspectorate advises keeping a tap supplied with unsoftened water for drinking (DWI), and the installation must meet the Water Supply (Water Fittings) Regulations 1999. Our commercial water softener specification guide covers bypass, backflow and drain details in more depth.
Questions to ask any supplier
- Is this flow figure an operating rating or a valve flow at a stated pressure drop?
- How many cubic metres will it soften between regenerations at my postcode hardness?
- What happens to supply during regeneration?
- How much salt does each regeneration use, and how often will I be filling the brine tank?
- What media is quoted, and why that one for my water?
- Who services the valves, meters and resin, and how often?
The Regal 750 datasheet, for example, gives 7.5 to 12 kg of salt per regeneration. On a big twin set the brine tanks hold 570 L each, so plan where the salt is stored and how it gets to the plant room.
If your site is smaller, our guide to sizing the Regal 100, 150 and 200 is the better starting point. For kitchen equipment, see our post on scale prevention in a commercial dishwasher. You can compare every model in the duplex water softener and Regal range, and our Comprehensive Maintenance plans cover the servicing.
FAQs
What is the difference between a duplex and a twin water softener?
A twin alternating set runs one vessel at a time and keeps the other in reserve, so soft water never stops. A duplex set runs both vessels together to carry a higher flow. Our datasheets quote the same vessels in either layout.
Do I need a twin softener for a hotel?
If the hotel draws softened water around the clock, usually yes. A single unit leaves the building on hard water each time it regenerates.
Is the Regal 500 bigger than the Regal 750?
No. The 500's 6.12 m³/h is a valve flow at a 1 bar drop and it ships without media. The 750 comes loaded with 75 L of resin and is rated at 3.5 m³/h with 15 m³ between regenerations.
Can I add another softener later?
Yes, on the right valves. A Clack system controller can link 2 to 6 units, so a site can grow from one or two vessels.
How much space does a Regal Twin 3672 need?
Allow for two tall vessels and two 570 L brine tanks, a connection height of about 2.4 m and a drain at about 2.5 m. We confirm the layout during the chargeable site survey.
Ready to size your site?
Send us your postcode hardness, a week of meter readings, your peak flow and a photo of the plant room. We will tell you whether a single unit is enough or whether you need twin or duplex duty. Get in Touch with our team.
Sources
- Thames Water, Hard water: https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
- Drinking Water Inspectorate, Domestic water filters and softeners: https://www.dwi.gov.uk/consumers/learn-more-about-your-water/domestic-water-filters-and-softeners/
- The Water Supply (Water Fittings) Regulations 1999: https://www.legislation.gov.uk/uksi/1999/1148/contents
- Sovereign Water datasheets: Regal 500 (SWC-REG500-25-R0), Regal 750 (SWC-REG750-26-R0), Regal Twin 3672 (SWC-RF3672TW-26-R0), Regal Duplex 3072 (SWC-RF3072DX-26-R0)
