What is the Best Mains Water Limescale Filter?

Hard water is a problem for many households in the UK, but it’s more widespread in the south and east of Britain. There are also pockets in Scotland, Wales, and northern England. Northern Ireland is lucky to have predominantly soft or only moderately hard water.

There’s a lot of confusion about hard and soft water. Strictly speaking, soft water is water that has an absence of dissolved minerals. Those minerals are usually calcium carbonate (CaCO3), magnesium carbonate (MgCO3), but can also contain low concentrations of bicarbonates and sulphates.

Conversely, hard water has high mineral content. Hard water isn’t a problem, it’s the limescale deposits that are the issue. And it’s also not very easy to prevent.

Let’s look at what can be done to prevent or reduce limescale.

Water Softeners

Water softeners have been around for a long time, and many people believe they are the only method of treating hard water.

The way they work is to replace the hard ions (the dissolved minerals) with sodium ions. The reaction takes place within an ion exchange resin inside the water softener vessel. That resin gets depleted quite quickly so must be regenerated regularly by backwashing using a brine solution.

The water softener has an electronic control unit that triggers the backwash cycle, usually in the middle of the night when there’s no requirement for any water use. To create the brine for the backwash the householder needs to add salt regularly. The period depends on the size of the softener and varies from 3 to 10 days.

Without this regular maintenance a water softener stops working. The resulting water will lather soap and detergents nicely. It won’t clog up your water heaters and appliances with limescale, but due to the increased level of sodium in the water it’s probably best not to drink it. That’s especially true if you have a heart condition such as hypertension (high blood pressure) or have a high salt diet.

A water softener is not a water filter and so it does not improve the quality of the water. However, if you’re looking for the best water filter for removing calcium then a water softener is as close as you’ll get.

Hard Water Filters

Mains water filters for hard water have improved greatly over the last few years.

One of the benefits of using a filter-based system for treating hard water is that it can be combined with other filtration stages easily to really improve the water quality through your entire home.

Sequestration Filters

Hard water filters come in two guises; the first uses food grade polyphosphate crystals that gradually release the phosphate onto the water to inhibit the formation of scale by chemical sequestration.

The sequestration method, is where complex phosphates combine with calcium and magnesium ions to form a stable compound to inhibit the creation of limescale.

This method works reasonably well, especially in slightly hard and moderately hard water regions.

Polyphosphate crystals can be added to carbon block filter cartridges to make a single stage hard water filter. 

These are low maintenance only requiring a cartridge change at 6 to 12 monthly intervals.

Electronic and Magnetic Devices

Limescale reduction systems that use magnetic fields are often hailed as the perfect solution. Low cost, they require no maintenance, just install, plug into the electricity supply, and leave it to get on with its job. That sounds like a magical solution, but electrical current, electro-magnets, and radio frequency type systems have failed to pass any scale control standards designed by recognised independent testing agencies.

There are conflicting reports from people who have bought and installed these types of scale control systems. The most positive results seem to be achieved by the manufacturers themselves.

We’ll allow you to make your own mind up.

TAC Filters

The third type of water filter to remove calcium and lime problems is generically called a TAC water filter. Template Assisted Crystallisation (TAC) is the latest method for treating limescale.

Developed in the early 2010s it has proven itself to be one of the most effective solutions for tackling limescale problems.

Hard water flows into a filter housing containing a cartridge about 30% full of TAC media. This is a white sand-like substance that circulates with the water in the filter cartridge and interacts with the dissolved carbonates. Those media granules have crystallisation sites where the hard ions are attracted. They combine to make microscopic crystals that detach from the media and then flow away.

Those microscopic crystals are inert so don’t “stick” and create limescale easily, thereby solving the problem. The bigger the TAC system the less frequent the maintenance – some last for 3 years before requiring a media change.

TAC water filters can be combined with other mains water filters to significantly improve water quality.

For example, the Doby Taste and OneFlow Hard Water Filter puts a carbon block filter in front of a TAC filter that uses Watts’ OneFlow TAC media. It filters out chemicals such as chlorine, PAHs, hormones and endocrine disruptors, trace pharmaceuticals and agricultural residues (among other things), and then in the second stage treats the limescale problem.

The Best Mains Water Limescale Filter - Conclusion

As you’ve seen, there is more than one filter to remove lime from water, and your own situation will vary from other peoples.

The best limescale filter for you needs to be considered carefully taking several things into account.

Heating hard water makes it particularly susceptible to forming limescale. This is why treating hard water extends the working life of boilers. Any appliance that’s fouled by limescale becomes much less efficient – up to 50% in many cases. So, installing either a mains water filter, or one dedicated to the hot water heater feed, will save you lots of cash.

It will also protect your plumbing, stripping out the existing scale, and restoring your water pressure and flow rate.

If you want to improve the taste of very hard water and reduce limescale problems, then a twin carbon block and TAC type of filter will be best.

On the other hand, in medium hard water areas your best mains hard water filter will be one containing polyphosphate (unless you don’t want that type, of course).

And finally, a water softener may be best if you want to remove the hardness entirely, although you’ll need to have an unsoftened supply to your kitchen cold tap and plan to carry out weekly maintenance.

Get in touch with Fountain Filters with no obligation. We will assess your needs and advise you of the best mains water limescale filter to effectively remove or reduce lime and calcium based on your home and your requirements.