The Water Conditioner Guide

What is Hard Water?

Many different dissolved salts can cause hard water, but the principal one that results in limescale is calcium bicarbonate. It is created by rainwater — which is slightly acidic — falling on calciferous rocks such as limestone or chalk and dissolving the calcium as it passes through the strata; the more dissolved calcium, the harder the water.

The most commonly used index to measure water hardness is calcium carbonate equivalent, rather than calcium content. If your hardness rating is measured in calcium, you can easily convert it to a calcium carbonate equivalent (CCE) by entering your calcium level below:

As the presence and quantity of calciferous rock varies, so does the level of calcium in the water supply, leading to wide variations of hard water levels across the UK.

What is Limescale, and Why Prevent it?

Calcium bicarbonate is the dissolved form of calcium created by rainwater. When this water is heated, the dissolved calcium bicarbonate reverts to its original rock-like state of calcium carbonate. What is unusual is that when this calcium carbonate forms it must adhere to a surface, and in doing so coats heating elements and pipes with layers of solid calcium carbonate. This is what we call limescale.

Limescale is about 400 times less conductive of heat than copper, so appliances can suffer significant reductions in efficiency and may eventually fail entirely due to heat stress. Just 1/8 inch (approx. 3mm) of limescale can equate to a 12 percent loss of heating efficiency.

The recent shift to renewable energy has seen a movement away from gas towards electric water heaters. Some of the design features that make these heaters so efficient also make them particularly prone to limescale formation, which has refocused attention on the problems caused by hard water.

An additional problem of vital importance to homeowners is the visible manifestation of limescale on showerheads, taps and other wetted surfaces. Limescale also holds dirt and bacteria, making fixtures unhealthy as well as unsightly.

What is a Water Softener?

Traditional methods of water treatment focus on the removal of calcium from the water by substituting it with sodium or potassium using an ion-exchange media. These processes are well understood and documented, and if the equipment is properly calibrated, maintained and supplied with salt, they are very efficient and effective.

However, they also have drawbacks. The initial cost for equipment and installation can be high, and regular maintenance and servicing is required to maintain efficiency — adding to this the on-going cost and labour of providing the essential salt to make the process work.

The biggest health drawback of a traditional salt water softener is the added sodium to the water supply. A separate drinking water supply is recommended, as the sodium-rich water is not good for general consumption and should never be used for baby formula milk, nor is it recommended for the elderly and those on a salt-restricted diet.

There are also environmental concerns. The contamination of wastewater by sodium and chloride effluent during regeneration restricts the opportunity for recycling the water, and has led to softener bans in drought-threatened parts of the world.

What are Physical Water Conditioners?

The use of physical water conditioners in the United Kingdom is widespread, with approximately 95 percent of commercial facility hard water treatment done by physical water treatment. Many are cost-effective, easy to install and require little or no maintenance, and the best products deliver high levels of limescale protection.

However, scepticism and a lack of understanding persists. Some is well founded, with a variety of ineffective products offered by suppliers who are often ignorant of the mechanisms and long-term performance of their own products. Even so, a significant amount of research and documentation is available for many of the more effective physical water conditioners.

Physical water conditioners come in many forms, but the feature they all share is that they generate nucleation seeds upon which limescale particles form. Once formed upon the nucleation seed they cannot adhere to any other surface — these microscopic particulates, suspended in the water, are harmlessly carried to an outlet with the flow of the water.

Types of Physical Water Conditioners

Magnetic and Electrolytic Water Conditioners

These generate zinc hydroxide, which is dosed into the water. Zinc is well established as a very effective nucleation seed onto which limescale can form in hard water; these devices use electrolysis to dose zinc from a sacrificial anode into the water flow. They are often the least expensive of the available water conditioners and can be very effective.

However, their lifespan is generally limited by two shortcomings. The first is that the zinc anode becomes depleted and needs replacing. The second, and more troubling, is that the zinc anode suffers from passivity — a tendency for the anode to become coated with contaminants in the water so the zinc corrosion process slows and eventually stops. This occurs more quickly in water with high levels of minerals other than calcium, such as iron and phosphates.

Typically in the UK, zinc-dosing devices may have a lifespan of just a couple of years, whereupon the conditioner requires replacing — and generally they have no way to indicate a replacement is required. It is also impossible to match the amount of zinc released to the hardness of the water unless sophisticated, expensive analysis and controls are employed. As a short-term solution they can be reasonably effective and inexpensive; for longer-term protection their performance can be disappointing.

Template-assisted Crystallization Water Conditioners

Template-assisted crystallization (TAC) uses conventional water softener tanks, sometimes in parallel, partially filled with a specially developed media that can stimulate limescale formation in cold water on the media.

The limescale grows larger by accretion until it breaks away from the media and is released into the water flow, going on to act as a nucleation seed to attract more limescale when the water is heated. Some versions of this process work better when the water around the media is heated.

The media is very vulnerable to contamination from phosphates, chlorine, iron and copper in the water supply, so its performance in any location is unpredictable unless protected by filtration. Generally, the life of the media is difficult to measure, so regular servicing is required when the media must be replaced.

Electromagnetic and Electronic Water Conditioners

Electromagnetic and electronic water conditioners act on naturally occurring minerals already held in solution in hard water, especially iron, to create nucleation seeds for limescale to form upon. Iron on its own is a weak limescale inhibitor, but if excited by a charge it can change its characteristics and act as a very effective nucleation seed.

Generally these devices take two forms. The first commonly generates a varying electromagnetic field and treats the water as it passes through, thereafter relying on a memory effect — a significant drawback, as the treatment may expire before the water has been heated. The second method uses radio waves that travel in the water both upstream and downstream, treating static or moving water without relying on a memory effect.

Some devices are plumbed into the water supply and use a high electrical load, while others use wires wrapped externally around the pipe and transmit an electromagnetic field or radio wave through the pipe material. An external installation means homeowners can fit the product themselves, accept unlimited flow rates and have no effect on water pressure. The leading models require no servicing or maintenance for a lifespan that can exceed 25 years, are inexpensive to run, and can even reduce and remove existing limescale — existing scale is not dissolved but exfoliates from the surfaces where it had previously formed.

One leading electronic water conditioner is so effective at generating nucleation seeds and reducing the dissolved calcium that it has been proven to result in chemically softer hot water — detectable through better lathering, less scum and improved skin conditions. Performance between models varies widely, and with pricing often an unreliable indicator, only manufacturers with performance verified by third-party, independent laboratories should be considered.

Tips on choosing a Physical Water Conditioner

With so much information on offer, here are our top tips on what to look for when purchasing a water conditioner:

• Price is not necessarily a good indicator of performance — some lower-priced products outperform more expensive ones.
• Ask the manufacturer for recent studies and independent third-party laboratory testing carried out by a trusted body.
• Look at design life (these vary widely), and check carefully what any guarantees cover — they may not relate to performance.
• Unless purchasing for a new build, check whether the product descales existing limescale.
• Check if the product requires a power socket.
• Does the product’s installation require a plumber?
• Get a clear idea of the maintenance requirements — ideally a good conditioner has no maintenance or servicing needs.
• Make sure you fully understand where the product should be installed; many have critical locations manufacturers are often unaware of.
• Look for a money-back guarantee.
• Be wary of products calling themselves “magnetic” — often just magnets cable-tied to the pipe that only work if there is a zinc anode in the water heater.