18 Litre Resin
1–11 People
Metered Control
Unit Only — Hoses Sold Separately
Quick-Connect Bypass Included
UK Manufactured
5 Year Parts Guarantee
The Calmag CalSoft Midi is a medium-sized, fully automatic metered water softener suitable for households of 1–11 people — the largest capacity domestic softener in the Calmag CalSoft range. With an 18-litre resin vessel, the CalSoft Midi is designed to handle the water demands of larger households, hard water areas, and installations where long intervals between regenerations are desirable. Manufactured in the UK by Calmag, it features the same proven metered demand control system as the CalSoft Mini but in a physically larger cabinet at 900mm high × 330mm wide × 470mm deep.
This listing is for the unit only — the CalSoft Midi is supplied with the quick-connect bypass valve but without installation hoses. A compatible 15mm or 22mm installation kit must be purchased separately (see the Standard 15mm Install Kit or Hi-Flow 22mm/19mm hose listings). This flexibility allows the softener to be ordered to suit the exact pipework configuration of each installation.
1–11
people
Household Size
⚠️ Unit Only — No Hoses Included. The CalSoft Midi is supplied with the quick-connect bypass valve but does not include installation hoses. You must also order a compatible installation kit: the Standard 15mm Install Kit (for gravity/conventional systems) or 19mm/22mm Hi-Flow Hoses (for combi, unvented, and Megaflow systems). See the related products in this catalogue.
Key Features
📦 18L Resin — Maximum Domestic CapacityThe largest resin capacity in the Calmag CalSoft range at 18 litres — ideal for large households, multiple bathrooms, or hard water areas where a higher resin volume reduces regeneration frequency and ensures a continuous supply of soft water.
💧 Metered Demand RegenerationRegenerates only when required based on actual water consumption — not on a fixed time schedule. Automatically learns and adapts to the household's water usage patterns, using only the salt and water needed for each regeneration cycle.
🔗 Quick-Connect Bypass IncludedSupplied with Calmag's quick-connect bypass valve featuring quick-release fittings and ¾" or 1" BSP adaptors. The integrated water meter within the bypass body saves installation space and simplifies setup.
🇬🇧 UK ManufacturedDesigned and manufactured in the UK by Calmag — a company built on consistent investment in stringent design, production and testing programmes, with a complete range of domestic and commercial water treatment solutions.
🔌 Simple Electronic ControlEasy-to-understand electronics require minimal setup — adjust the water hardness level if required, and the unit handles regeneration automatically. Digital display provides clear operational status at all times.
🔒 5 Year Parts Guarantee5-year parts guarantee. Extended warranty options also available. All softeners are built and wet-tested before despatch to exacting manufacturing standards.
💰 Long-Term Running EconomyWith an 18L resin capacity, the CalSoft Midi regenerates less frequently than smaller units — meaning lower total salt and water consumption per month for equivalent softening performance. Estimated £200/year saving for an average household of four from reduced scale, cleaning products, and appliance maintenance.
🏠 Suitable for All Plumbing SystemsSuitable for all plumbing configurations when paired with the appropriate installation kit — gravity-fed vented systems (15mm kit), combi boiler systems, unvented pressurised cylinders, and Megaflow systems (22mm/19mm hi-flow hoses).
Technical Specifications
| Specification |
CalSoft Midi Detail |
| Resin Capacity |
18 litres |
| Dimensions (H × W × D) |
900mm × 330mm × 470mm |
| Household Size |
1–11 people |
| Max Flow Rate (15mm kit) |
50 l/min |
| Max Flow Rate (22mm kit) |
70 l/min |
| Max Pressure |
5 bar |
| Min Inlet Pressure |
1.5 bar |
| Max Water Temperature |
43°C |
| Inlet / Outlet Connection |
¾" BSP or 1" BSP |
| Preferred Salt Type |
Tablet |
| Installation Kit |
Not included — order separately (15mm or 22mm/19mm) |
| Bypass Valve |
Quick-connect bypass included (meter integrated) |
| Parts Guarantee |
5 years |
| Labour Guarantee |
12 months |
| Electrical Supply |
Standard UK mains supply required |
| Brand |
Calmag |
Frequently Asked Questions
What installation kit do I need for the CalSoft Midi?
For conventional gravity-fed or vented systems, order the Standard 15mm Install Kit (sold separately). For combi boiler, unvented, pressurised, or Megaflow systems, order the 19mm Hi-Flow Hoses (pair) or 22mm high-flow kit (sold separately). The bypass valve with integrated meter is included with the softener unit itself — only the hoses need to be purchased additionally.
How does the CalSoft Midi compare to the CalSoft Mini?
The CalSoft Midi has a larger 18L resin capacity (vs 12.5L for the Mini) and a larger physical footprint at 900mm high vs the Mini which fits under a kitchen sink. The Midi is therefore better suited to larger households (up to 11 people vs 8 for the Mini) and properties in hard water areas where a larger resin volume means fewer regenerations. The Mini is the more popular choice for typical domestic installations where under-sink fitting is important.
Can the CalSoft Midi be installed in a garage?
Yes — provided the installation space is frost-free. The CalSoft Midi should not be installed in locations where it may be exposed to freezing temperatures, as this could damage the resin and valve assembly. A garage with adequate insulation or heating is acceptable.
⚠️ Note: Unit only — no installation hoses included. Order the Standard 15mm Install Kit or 19mm Hi-Flow Hoses (PAIR) separately to complete the installation. Quick-connect bypass valve with integrated meter is included. A separate unsoftened drinking water tap is required under Building Regulations. Requires standard UK mains power supply.
