Brands such as BWT and Calmag water softeners for hard water areas, complete installation kits, and drinking water filter systems — everything needed to protect your home's plumbing and appliances from limescale.
BWT Range Calmag Range Part G Compliant Hard Water Solutions Drinking Water Filters
Hard water affects over 60% of homes in England — including the majority of properties in the South East, East Anglia, the Midlands, and Yorkshire. It's measured in parts per million (ppm) of dissolved calcium and magnesium carbonate, and above 200ppm, the effects become significant: limescale builds up inside boilers, hot water cylinders, heat exchangers, pipework, and appliances; shower screens and bathroom surfaces develop white film deposits; soaps, shampoos, and detergents lather less effectively; and energy bills creep up as scale-insulated heat exchangers work harder to reach temperature. A correctly specified and installed water softener eliminates all of these effects at the point of entry, protecting the entire household water system downstream.
This collection covers the full range of products needed to specify, install, and maintain a softened water system — from the softener unit itself through to installation kits, drinking water filters (softened water is not recommended for drinking in its treated form), and replacement consumables.
BWT Water Softeners — The WS Range
The BWT WS range represents the current generation of BWT domestic water softeners — metered, salt-efficient, and engineered for UK water conditions. All three models share the same core technology: AMECS metered demand control, a Millennium Rotary Valve for durability, 72-hour memory backup, block and tablet salt compatibility, and Part G Building Regulations compliance. The differences are in flow rate capacity and resin volume — choosing the right model means matching the softener to your system's peak demand.
| Model |
Resin Volume |
Peak Flow Rate |
Install Kit |
Best For |
| BWT WS355 |
14L |
30 l/min |
15mm kit included |
Gravity-fed and conventional boiler systems, 1–6 people |
| BWT WS455 |
10L |
50 l/min |
22mm kit included |
Combi boilers, unvented cylinders, Megaflow — 1–6 people |
| BWT WS555 |
14L |
50 l/min |
22mm kit included |
Combi/unvented systems, larger households — up to 11 people |
🔑 Which BWT Softener Do You Need?
The key decision is flow rate, not resin volume. If you have a combi boiler, unvented hot water cylinder, or Megaflow system, you need the hi-flow WS455 or WS555 (50 l/min) — the WS355 at 30 l/min will restrict flow from a high-pressure mains-fed system. If you have a conventional (gravity-fed) boiler with a header tank, the WS355 is the appropriate specification. Between the WS455 and WS555: if your household is up to 6 people on a combi/unvented system, the WS455 is sufficient. For larger households (up to 11 people) or where maximum regeneration capacity is needed, the WS555's 14L resin volume provides greater capacity between regeneration cycles. All three models include a free @Home commissioning visit from BWT — register within 100 days of purchase for the extended 5-year parts / 2-year labour warranty.
Calmag Water Softeners — CalSoft Range
The Calmag CalSoft range provides an alternative to BWT with quick-connect bypass technology, a 5-year parts warranty, and models available both with and without installation hardware. Key features across the range include an integrated flow meter within the quick-connect bypass (saving 5" of installation space versus traditional bypass valves), metered demand regeneration, and compatibility with both ¾" and 1" BSP connections.
💧 CalSoft Mini c/w 22mm Hi-Flow Kit
The CalSoft Mini is the flagship domestic softener in the Calmag range — supplied complete with a 22mm hi-flow installation kit (70 l/min maximum) as standard, making it ready for combi and unvented systems straight out of the box. 12.5L resin, 2000L capacity at 300ppm, suitable for 1–8 people. The integrated quick-connect bypass with built-in meter saves installation space and simplifies servicing. Replaces the previous Calsoft M model.
💧 CalSoft Midi — Unit Only
The CalSoft Midi is the larger-capacity unit for households up to 11 people — 18L resin. Supplied as a unit only (no hoses) for installers who are supplying their own pipework or using existing connections. Pair with the Calmag Standard 15mm Install Kit for gravity-fed/conventional systems (max 50 l/min), or the Calmag 19mm Hi-Flow Hoses for combi/unvented/22mm systems (max 70 l/min).
Calmag Softener Installation Accessories
Standard 15mm Install Kit For CalSoft Mini and CalSoft Midi. Suits gravity-fed and conventional boiler systems. Max 50 l/min. Includes 15mm hoses and valves. Bypass valve not required — supplied with the softener unit.
19mm Hi-Flow Hoses (Pair) For CalSoft Mini and CalSoft Midi on combi, unvented, Megaflow, and 22mm systems. Inlet and outlet hose pair. Max 70 l/min. For full flow from high-pressure mains-fed systems.
Drinking Water Filter — CalFresh C System
Softened water replaces calcium and magnesium ions with sodium ions — it tastes different from unsoftened water and is not recommended for drinking, particularly for individuals on sodium-restricted diets, for preparing baby formula, or for filling kettles (sodium is harder to descale than calcium). It is therefore best practice — and in many installations a Building Regulations requirement — to maintain an unsoftened supply to at least one drinking water tap, typically at the kitchen sink.
Where an unsoftened drinking water point is available but water quality is still a concern — for taste, odour, chlorine, or trace contaminants — the Calmag CalFresh C Drinking Water Filter provides a complete under-sink filtration solution:
🚰 CalFresh C Drinking Water Filter Kit
Complete under-sink kit including filter housing, 10" Fresh C carbon block cartridge, dedicated drinking tap, and all fittings. Filters chlorine, taste, odour, sediment, bacteria, cysts, and heavy metals. No power required. Cartridge life 4–6 months. Lifetime housing guarantee on registration.
🔄 Fresh C Replacement Cartridge (CART-FRESH-C)
Replacement 10" carbon block cartridge for the CalFresh C kit. Replace every 4–6 months depending on usage and local water quality. Cartridge only — the housing is reused. MPN: CART-FRESH-C.
Calmag Part L Compliant Heating Pack
While not strictly a water softening product, the Calmag Part L Compliant Heating Pack is the natural companion product to any new or replacement boiler installation in a hard water area. Building Regulations Part L requires that heating systems meet minimum efficiency standards — which includes inhibitor treatment and, in hard water areas, scale prevention. This five-component pack covers every requirement in a single order:
- 22mm central heating filter
- 500ml BuildCert inhibitor (central heating)
- 500ml system cleanser
- WRAS-approved filling loop
- 15mm electrolytic scale inhibitor
Suitable for systems up to 10 radiators / 100L. Covers the scale inhibition, inhibitor dosing, filter installation, and system cleaning requirements of Part L in a single product.
Why Install a Water Softener?
🔥 Boiler and Cylinder Protection Limescale on a heat exchanger acts as insulation — a 1mm layer of scale reduces heat transfer efficiency by approximately 7%. Over time, scale accumulation increases energy consumption, reduces hot water output, and ultimately causes premature boiler failure.
🧼 Better Lathering — Less Detergent Soft water lathers far more readily than hard water. Most households use 50–75% less soap, shampoo, and detergent after softener installation — a significant ongoing saving that partially offsets the cost of salt.
🪟 No Limescale on Surfaces Shower screens, taps, basins, and tiles stay clear of white film deposits. Cleaning time reduces significantly. Chrome and glass shower screens — notoriously difficult to keep clear in hard water areas — maintain their appearance indefinitely.
🧺 Appliance Longevity Washing machines, dishwashers, and kettles last significantly longer in softened water conditions. Heating elements, which are the most scale-vulnerable component in any appliance, are protected from the point of installation.
💧 Softer on Skin and Hair Many people with eczema, sensitive skin, or dry hair notice significant improvement after switching to softened water. Hard water reacts with soap to form an insoluble curd that remains on skin and in fabric — softened water rinses completely.
📋 Part G Compliance All BWT WS and Calmag CalSoft softeners are Part G Building Regulations compliant — they incorporate an unbypassable non-return valve to prevent salt contamination of the supply in the event of backflow. Required for any new installation in England and Wales.
Water Softener Installation — What to Know Before Buying
📍 Installation Position
A water softener should be installed on the rising main, after the stop tap and after any branch to a drinking water tap (or with a separate unsoftened branch to the kitchen cold tap). It must be installed indoors, in a frost-free location, with access to a drain for the brine discharge from regeneration cycles. Standard installation requires a 15mm or 22mm mains supply (depending on model), a power socket within range for the control valve, and adequate floor or cabinet space for the unit and salt block or tablet storage.
🧂 Salt — Block vs Tablet
All BWT WS and Calmag CalSoft softeners are compatible with both block salt and tablet salt. Block salt (two 4kg blocks per regeneration cycle) is the most convenient format — no measuring, no pouring, and less risk of bridging in the brine tank. Tablet salt is widely available and typically lower cost per kilogram. The WS555 uses 0.6–2.0kg of salt per regeneration cycle depending on water hardness; other models are similar. Running cost for a typical household is in the region of £50–100/year in salt.
Frequently Asked Questions
Can I drink softened water?
Softened water is safe for most adults but is not recommended as a primary drinking water source for infants, people on sodium-restricted diets, or for preparing baby formula — the ion exchange process adds a small amount of sodium to the water. Best practice (and often a planning requirement) is to maintain an unsoftened drinking water tap in the kitchen. For taste and purity improvement of the unsoftened supply, pair your softener installation with a CalFresh C under-sink drinking water filter.
How do I know if I have hard water?
Water hardness varies significantly by region and is determined by the geology of the local water source. A hardness level above 200ppm (milligrams per litre) is generally considered hard; above 300ppm is very hard. You can check your local water hardness on your water supplier's website, or contact us — we can advise on typical hardness levels for your postcode area. Visible signs include rapid kettle scale, white deposits around taps and showerheads, and poor lather from soap.
How often does a water softener need servicing?
BWT WS softeners are supplied with a free @Home commissioning visit and come with a 5-year parts / 2-year labour warranty when registered within 100 days. Beyond warranty, an annual service check is good practice. The main consumable is salt — this needs topping up periodically (frequency depends on hardness and household usage). The control valve may require periodic servicing after 5–10 years depending on water quality and usage.
Does a water softener reduce water pressure?
A correctly specified softener will not perceptibly reduce flow or pressure. This is why flow rate is the key specification criterion: the BWT WS455 and WS555 and the Calmag CalSoft Mini are all rated to 50–70 l/min, which is well above the peak demand of any domestic system. Installing a 30 l/min softener on a combi boiler system with 22mm pipework would restrict flow and should be avoided — use the WS455, WS555, or CalSoft Mini instead.
What's the difference between a water softener and a scale inhibitor?
A water softener uses ion exchange to remove calcium and magnesium ions from the water entirely — the water downstream is genuinely soft, lathers readily, and will not deposit limescale anywhere in the system. A scale inhibitor (such as the electrolytic type in the Calmag Part L pack) modifies the behaviour of calcium carbonate to reduce its tendency to adhere to surfaces — it does not remove hardness ions, and softened lathering benefits are not achieved. Inhibitors are appropriate for protecting heating system components; a softener is the correct solution for whole-house limescale elimination.
ℹ️ Not sure which softener is right for your system? The correct choice depends on your system type (combi, conventional, unvented), your household size, and your local water hardness. Contact us with these details and we'll recommend the right product — and confirm whether you need a 15mm or 22mm install kit for your pipework.
