The quality of your water is of utmost importance to us. The infographic below shows what is involved in treating the water you drink to make it safe.

To get a detailed water quality report for your specific postcode area, please click on the link below.

Water quality /hardness checker


  1. Screening

    Water passes through fine screens, removing larger material such as sticks and weeds.

  2. Aeration

    This process removes compounds such as hydrogen sulphide and carbon dioxide, and oxidises dissolved metals.

  3. Primary Treatment

    A chemical is added to make the unwanted particles in the water stick together. This process forms small particles called 'floc', which attract impurities.

  4. Clarification

    The floc is stirred to increase the size of the particles, which radily sink to the bottom and are removed.

  5. Filtration

    Water flows through deep sand filters. These filters remove the smallest particles from the water.

  6. Sludge Treatment

    Waste products produced during the treatment processes are themselves treated, with clean water returned to the environment and solid matter recycled into fertiliser.

  7. Advanced Treatment

    Ozone gas is bubbled through the water which then flows through granular activated carbon (GAC) absorbers. These processes break down and remove pesticides and other compounds which may cause an adverse taste and odour to the water.

  8. Disinfection

    Ultra-violet light is used at many of our works to inactivate natural microscopic organisms. Fianlly we use small quantities of chlorine to disinfect all water supplies, to eliminate potentially harmful micro-organisms such as basteria.

  9. To your tap

    The treated water is pumped from the treament works directly to customers and is also stored in underground reservoirs and water towers ready for periods of high demand.

Good to know

  • 521 million litres of water a day – that’s how much water we supply to around 2.2 million people
  • 83 water treatment works – that’s how we ensure our water is of the highest quality 

  • 500,000 water quality tests each year - that’s how we ensure your water meets the highest standards

  • 9,000 miles of water mains – that’s how we transfer fresh drinking water direct to your tap

Cloudy or discoloured water

During its journey to your taps, there are a number of ways in which the appearance of your water may be affected, and occasionally it can become discoloured.

The most common cause of discolouration is a change in the flow or pressure within the pipes – for example as a result of a burst main in your area. The change in pressure can dislodge tiny deposits such as iron or manganese sediments, which may turn the water brown for a short period.

Your water may also appear cloudy, or white, on occasion. If you fill a glass of water and it clears from the bottom upwards then this means your water is just  a little more aerated than usual. The bubbles will disappear if the water is left to stand.

In most cases, discoloured water is not harmful and can be cleared by running the cold kitchen tap at a steady flow until it clears. If the water does not clear after 20 minutes, please contact us for advice.

Taste and odours

Occasionally, our customers report that their tap water suddenly has an unusual taste or odour. We've set out the most common causes of this below.


We add small, carefully controlled amounts of chlorine at the treatment works to disinfect the water and a residual is maintained throughout the distribution system to make sure it's safe to drink. Please rest assured that chlorine isn't harmful in the quantities we add and we aim to keep chlorine levels to a minimum.

The chlorine may be more noticeable on some occasions depending on a number of factors, for example: distance from the treatment works, the time it takes the water to travel to your property and the time of day.

If you do have strong TCP tastes or smells from your water, please try the following:

  • Check with your neighbour to see if they have same problem
  • Make a note of which tap or fitting you were using when the problem started
  • If necessary, replace the washer or fittings
  • Rinse your kettle out before you use it
  • If you suspect your kettle may be causing the taste, try boiling the water in a saucepan and use this water to make your hot drinks
  • If you have a washing machine plumbed into the mains in the kitchen, check it has a suitable non-return valve fitted so that water sitting in the hose over long periods is not drawn back

Musty tastes or earthy smells

Musty tastes/smells are often caused by water that has been left stagnant after periods of non-use.You can also experience a musty taste when cold water pipes pass near unlagged hot water pipes or radiators where they can become warm. Running your tap for a couple of minutes will bring fresh cold water through.

If you notice this smell or taste for the first time, try using a mild household disinfectant to wash outside and inside your drinking water tap. But don’t forget to let it run a little before you use it again to rinse out the disinfectant.

Metallic tastes

A metallic or bitter taste can arise from copper, iron or galvanised pipes that have either not been fitted properly, or may have corroded.

If the water has been standing for several hours in the pipe, fill a washing-up bowl with water to draw fresh water through the pipe. Top tip! The water in the bowl can then be used for watering your garden plants so it's not wasted.

Water hardness

To find out what the water hardness rating is where you live, please click here.

The hardness of your water depends on the amount of calcium it contains. The higher the levels of calcium, the harder the water.

Water hardness varies from region to region, depending on the amount of minerals which dissolve in rainwater as it soaks through the ground. Most of the water we supply in Southern England comes from underground chalk aquifers, so the water is hard.

This doesn't affect the quality of your drinking water or the performance of soaps and detergents, although it can lead to a build-up of limescale in kettles, boilers and hot water pipes.

Inhibitors, conditioners and softeners

There are a number of products available which either slow down the formation of limescale or actively soften the water. These products work through a combination of chemically slowing down or removing limescale from the mains water.

Softeners can significantly increase sodium levels in water, so if you want to use a water softeners, always make sure that there is a supply of un-softened water coming into your home for drinking purposes.

Rather than interfere with the natural hardness of the region’s water, we leave it up to you to decide whether artificial softening is the right choice. 

Lead pipes

If you live in a house built before 1970, chances are you may have lead pipework or lead solder may have been used, it is possible that you have lead pipes linking your home to our water network. Homes built since then tend to have copper or plastic pipes. If pipes in older properties have been replaced since the 1970s, lead will not have been used.

Your drinking water can pick up lead from the pipework that runs from the water main underground and into your property, or from lead pipework inside your property.

Lead is less of a problem in hard water areas such as ours because a layer of limescale builds up between the pipe and the water, preventing the lead dissolving into the drinking water.

Lead is harmful if excessive levels are allowed to build up in the body, so it makes sense then to make sure we consume as little lead as possible – pregnant women and young children (under the age of 6) are especially vulnerable to the risk of lead, here are some ways to minimise lead dissolving from your pipe work into the drinking water:

  • Only use water from the kitchen cold tap for drinking and cooking, as hot water dissolves more lead than cold
  • Never cook or mix infant formula using water from the hot tap
  • Run the tap for a few minutes before you use the water and make sure you feel the temperature drop before cooking, drinking or brushing your teeth. This is especially important if the water has been standing for a long time in the lead pipes, such as overnight
  • Avoid disturbing or knocking lead pipes. Such mechanical action can generate particulate lead
  • Do not lay hot water pipes alongside or close to cold water pipes


Not a drop of water supplied by us has fluoride artificially added.

Does that surprise you? You won't be alone as we've found quite a few customers think we do.

In some parts of the UK, and in other countries around the world, the decision has been made to artificially add fluoride to water supplies because it is considered to have benefits in terms of reducing tooth decay.

This is not the case in our area and we don't ever add fluoride to your water.

Fluoride facts

Fluoride is a naturally occurring substance found in soils and rock. Very low levels can be naturally present in water throughout the country.

Fluoride can greatly help dental health by strengthening the tooth enamel, making it more resistant to tooth decay. It also reduces the amount of acid that the bacteria on your teeth produce.

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