Overview | Is this right for me? | What it reduces | How it works | Specs | What's included | Installation | Maintenance & costs | FAQs | Reviews

• How Hard is My Water? - find out how hard your water is and what it means for your home.
• OneFlow Anti-Scale System FAQ - the questions we get asked most about OneFlow, answered.

Overview

The Boiler Descaler 18 Lpm is a compact, salt-free limescale protection system for smaller homes in hard water areas. Using template assisted crystallisation (TAC), it conditions hardness minerals so they're less likely to form hard scale on boilers, water heaters, pipework and appliances; without actually softening the water.

• Helps protect boilers and hot water systems from damaging limescale build-up.
• 18 litre per minute flow rate, suitable for homes up to 3 bedrooms with 1-2 bathrooms.
• Salt-free TAC technology retains naturally occurring calcium and magnesium while controlling scale.
• No salt, chemicals, electricity or wastewater - simple to run with no brine tank or backwashing.
• Low maintenance - replace the OneFlow cartridge approximately every 1-2 years, depending on water usage and quality.

Live in a hard water area? - If you've had to buy a new kettle every year or two, your boiler is quietly suffering the same fate.

Is this right for me?

Choose this if

You live in a hard water area and want to protect your boiler, hot water system, pipework and appliances from limescale without installing a conventional water softener. The 18 Lpm model is best suited to smaller homes with up to 3 bedrooms and 1-2 bathrooms, where scale protection rather than softened water is the priority.

Not ideal if

You have a larger home or need a flow rate above 18 litres per minute, in which case one of our higher flow OneFlow systems will be more suitable. It's also not the right choice if you want soft water, as TAC controls limescale without removing the calcium and magnesium that cause hardness. In this case a water softener would be the better choice.

If you also want to reduce chlorine and improve taste and odour, choose a system that combines carbon filtration with OneFlow scale protection.

What to check before buying

• Property size: Designed for homes up to 3 bedrooms with 1-2 bathrooms.
• Flow rate: Maximum recommended flow rate is 18 litres per minute. Choose a larger system if your household regularly requires more.
• Available space: Allow approximately H 47cm x W 20cm x D 22cm, plus room for pipe connections and future cartridge changes.
• Connections: The housing has 1'' BSP female ports. Choose a 15mm or 22mm connection kit, with or without isolating flexis, or select no connections if you're supplying your own.
• Water hardness: OneFlow is designed for hard water up to 427 ppm (25 grains per gallon) as CaCO3. If you're unsure how hard your water is, check with your water supplier or contact us before ordering.

What it reduces and what it doesn't 

The Boiler Descaler is designed specifically for limescale control in hard water areas. Using OneFlow TAC technoloty, it conditions naturally occurring hardness minerals so they're less likely to attach to boilers, heating elements, pipework and appliances as hard scale.

The Boiler Descaler helps reduce:

• Limescale formation - on boilers, water heaters, immersion elements, pipework, valves and appliances.
• Hard scale build up - caused by calcium and magnesium in hard water.
• Existing scale deposits over time, as treated water can help loosen scale already present within the plumbing system.

The Boiler Descaler doesn't reduce:

• Water hardness - calcium and magnesium remain in the water, so it isn't a water softener.
• Chlorine, taste or odour - there is no activated carbon filtration stage.
• Fluoride
• Bacteria or other micro-organisms
• Sediment, heavy metals or other drinking water contaminants

OneFlow is a scale control system rather than a water softener or drinking water purifier. It retains naturally occurring calcium and magnesium and requires no salt or chemicals to control limescale.

How it works

The problem: scale is costing you money

In hard water areas, naturally occurring calcium and magnesium can form limescale when water is heated. Over time, scale can build up on boiler components, heating elements, hot water cylinders, pipework and appliances.

This hard deposit can restrict water flow and act as an insulating layer on heat-transfer surfaces, making water heating equipment work less efficiently. It can also contribute to premature wear and increase the amount of cleaning and maintenance needed around the home.

Preventing scale from forming is therefore much easier than dealing with heavy limescale once it has built up.

The solution: template-assisted crystallisation

OneFlow uses template assisted crystallisation (TAC) to control limescale without removing the calcium and magnesium from your water.

As hard water passes through the cartridge, hardness minerals interact with specially designed nucleation sites on the TAC media and form microscopic crystals. These crystals detach from the media and remain suspended in the flowing water, making the minerals much less likely to attach to surfaces as hard limescale.

The process requires no salt, chemicals, electricity or wastewater, and because the hardness minerals aren't removed, the water isn't softened. You retain the naturally occurring calcium and magnesium while helping protect your boiler, hot water system, pipework and appliances from scale.

Specifications

Technology	Template-assisted crystallisation (TAC) for salt-free limescale control
Cartridge	White canister containing 750ml of OneFlow anti-scale media
Cartridge size	4.5" x 10"
Recommended flow rate	Up to 18 litres per minute
Suitable for	Homes up to 3 bedrooms with 1-2 bathrooms
Maximum water hardness	427 ppm (25 grains per gallon) as CaCO3
Maximum operating pressure	125 PSIG (approx 8.6 bar)
Operating temperature	10ºC - 52ºC (50ºF - 125ºF)
Connection size	Standard 1" BSP female ports; 15mm and 22mm connection kits available
Dimensions	H 40cm x W 20cm x D 20cm; allow H 47cm x D 22cm when installed, plus space for port connections
Salt required	None
Electricity required	None
Wastewater	None
Certification	Tested and certified to NSF/ANSI Standard 42 (materials only); FDA grade components and materials
Maintenance	Replace the OneFlow cartridge every 1-2 years

Performance depends on local water chemistry, flow rate, system design and application. Performance claims apply when installed as a complete system connected to a pressurised water supply.

What's included

Everything you need for the main filter assembly is included, with a choice of connection kits to suit your plumbing.

• 1 x 4.5'' x 10'' big blue filter housing with 1" BSP female ports
• 1 x white mounting bracket
• 1 x OneFlow cartridge containing 750ml of TAC anti-scale media
• 1 x housing spanner
• Fitting instructions

Choose your connection kit when ordering: 15mm or 22mm fittings, with or without isolating flexis, or select no connections if you're supplying your own.

Installation & placement

The Boiler Descaler is installed inline on the incoming cold water supply, before the boiler or hot water system, so the water is treated before it's heated and limescale has the opportunity to form.

Allow approximately H 47cm x W 20cm x D 22cm, plus sufficient room for pipe connections and future cartridge changes. The housing has standard 1'' BSP female ports, with optional 15mm and 22mm connections kits available.

Installation is a straightforward water in / water out arrangement and requires no electrical connection, drain or wastewater pipe. We recommend having the initial installation carried out by a competent plumber; after that, routine cartridge changes are straightforward.

Important: Before installatioon, soak canister containing the OneFlow TAC media in water for two hours. This allows the media to hydrate properly and helps prevent smaller particles being lost into the pipework when the system is first commissioned.

Full fitting instructions are supplied and can also be downloaded from the product page.

Maintenance & running costs

The Boiler Descaler is low maintenance, with no salt to top up, electricity to pay for or backwashing required. The main ongoing cost is replacing the OneFlow TAC media.

Replace the OneFlow cartridge approximately every 1-2 years, depending on water quality and household usage. Once the system has been installed, routine replacement is straightforward and can normally be carried out yourself without calling a plumber.

You can replace either the complete OneFlow cartridge or purchase 750ml of replacement TAC media to refill the existing canister.

We'll send you an email every six months to remind you to check your system, and we recommend inspecting the housing O-ring whenever the cartridge is changed and replacing it approximately every 2-3 years.

FAQs

Is a boiler descaler the same as a water softener?

No. The Boiler Descaler uses template assisted crystallisation (TAC) to help control limescale without removing the calcium and magnesium that make water hard. Your water therefore remains hard, but the minerals are less likely to form hard scale on boilers, heating elements, pipework and appliances.

What size home is the 18 Lpm Boiler Descaler suitable for?

The 18 litre per minute model is designed for smaller properties with up to 3 bedrooms and 1-2 bathrooms. If your home is larger or regularly requires a higher flow rate, choose one of our higher flow OneFlow systems.

Does it remove existing limescale?

OneFlow is primarily designed to prevent and control new scale formation. Treated water may also help loosen existing scale deposits gradually over time, but it shouldn't be considered a chemical treatment for removing heavy existing limescale from a badly scaled boiler or appliance.

Does it remove chlorine or improve the taste of my water?

No. This system contains TAC scale control media rather than activated carbon, so it isn't designed to reduce chlorine, taste or odour. If you want both chlorine filtration and limescale protection, choose a system that combines a carbon block cartridge with OneFlow TAC technology.

How often does the OneFlow cartridge need replacing?

Replace the OneFlow cartridge approximately every 1-2 years, depending on your water quality and household usage. You can replace the complete cartridge or refill the existing canister with 750ml of replacement TAC media.

Watts components are sometimes replaced with other similar quality items due to supply chain issues. Brassware and other plumbing accessories are sourced from UK suppliers.

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