Serving parts of North West London and the Home Counties.


Water Hardness

General information on water hardness

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The type of water that we supply is classed as 'hard' water. This hardness occurs naturally and does not vary much over time.

When rainwater, which is naturally soft, falls on the ground it passes through the underlying rocks and some minerals dissolve into it. Over 60% of our water supplies are from groundwater taken directly from the part of the rock known as an aquifer.

There are no standards for hardness in the Water Quality Regulations, neither are there any health based standards for the hardness of drinking water as hard water is perfectly safe to drink. There is even a lot of evidence to suggest that hard water is actually good for your health as it can provide many of the natural minerals that your body needs. Unless there are specific requirements to do so, there is no need to soften your water.

Click here to view a map of water hardness across the UK.

For information on the hardness in your area please click here.


Upon heating, hard water produces ‘scale’ and so hot water systems, kettles, electric irons and domestic appliances are particularly prone to ‘scaling up’.

Hard water can also leave ‘tide marks’ on basins, sinks, baths and toilets and a scum on the surface of hot drinks, especially tea brewed in the cup with a teabag (due to the air and oil in the tea). Scale and scum is not harmful, but we appreciate you may find it aesthetically unpleasing.


To reduce the build up of scale:

  • In kettles – don’t re-boil any water left in a kettle that has previously been boiled, refill with fresh water from the tap or from a jug kept in the fridge. Only using the amount of water that you need.

  • In hot water and heating systems – adjust the temperature that the water is heated to 60oC. This will not only save you money, but also reduce the risk of scalding from the water being too hot.

We are unable to advise on the use of de-scaling products. However, if you do decide to use a de-scaling product, please take care to follow the manufacturer’s instructions. Be aware that in the short term there might actually appear be an increase in the amount of scale you notice in the water after it has been heated. This is because the scale that comes out of the water has no available scale layer to adhere to.

Should I fit a water softener?

Not all of our customers want softened water so we leave this decision as a matter of individual choice. Hard water produces less lather from soap, washing up liquid and washing powders. If you feel you would like the water ‘softened’ you can consider installing a domestic water softener. We are not in a position to offer advice to customers on makes or types of water softener and would recommend customers wishing to install a water softener to contact a Watersafe plumber. Further independent information on water softeners can be found here.

Please remember, if you are considering installing a water softener we would recommend you keep a separate un-softened mains fed tap for cooking and drinking purposes as most softeners replace the calcium and magnesium with sodium. This can be a particular problem for premature babies and for people who are on a low sodium (low salt) diet. Artificially softened water may also be more aggressive to plumbing causing increased leaching of copper and lead into water as it stands in pipework.

Common problems with water softeners

One common problem associated with domestic softeners is when there is ‘breakthrough’ of resin beads from the softener. The beads, which are usually small, round, light coloured balls can then be drawn through in the cold water supply. In cases such as this, you should contact the manufacturer or installer of the unit to rectify the problem.

Jug Filters

Some jug filters contain ion exchange resin beads which alter the hardness of water so the filtered water produces less scum after boiling. Sometimes the carbon held in the filters , which look like small, black particles can be forced back through the top of the filter and onto the top of the jug. This gives the impression that there are black bits in the water coming from your tap. You can check whether this is happening by filling a glass with water before filling the jug filter – as long as the water is clear before you put it in the jug filter you can be assured that there is nothing wrong with the quality of the mains water. Changing the filter will usually solve this problem.

Water Conditioning devices

Water conditioning devices come in a wide range of products and are designed to reduce the build up of lime-scale deposits on heat-exchange surfaces when hard water is heated. These devices do not soften water. There are many types of these devices on the market e.g. magnetic and electronic, with a variety of claimed operating mechanisms. It is generally understood that water conditioners are not completely effective in preventing lime-scale build-up – they reduce scale build-up by modifying the form of the scale produced making it less likely to stick on heat-exchange surfaces. These devices appear to be most beneficial when they are fitted to the water inlets to boilers and other water heating devices. Should you wish to have a unit fitted, we would advise you use a reputable manufacturer or dealer.


For more useful information visit the Drinking Water Inspectorate>>