From source to tap - We uncover the science of water for British Science Week! - 15/03/2017

Sutton and East Surrey Water -

Wednesday 15 March 

Where does our water come from?

When it rains, water runs into streams and rivers and soaks into the ground. In spring and summer, much of it evaporates or is used by plants and trees. In winter, the rain seeps into the topsoil and into the rock beneath the surface. This water-holding rock, or aquifer, acts like a giant sponge, holding the groundwater within it.

The rock is either chalk or greensand and we abstract water using boreholes sunk at a depth of between 90m-180m. The water is pumped to the surface, and then pumped to our treatment works. We have seven works which treat groundwater supplies which provides 85% of our water; the other 15% comes from our reservoir at Bough Beech, near Edenbridge, which is filled from the River Eden in Kent, during the autumn and winter.

So how do we treat our water?

Because of the chalk and greensand acting as a natural filter, the water from our boreholes is of high quality. But we still need to purify it before it is safe to drink. We improve the quality of the water by a treatment process called ‘softening’.

The water extracted from our boreholes is known as ‘temporary’ hard water. That means that it contains dissolved minerals, mainly calcium and magnesium bicarbonates, which produce a ‘scum’ when mixed with soaps and detergents. Also, when hard water is heated, a solid precipitate called ‘scale’ is produced. Softening reduces the amount of soap and other detergents needed. It also reduces scaling in tanks, boilers and kettles. 

Have a look at the water treament process in full:

Tuesday 14 March 

Today we’re educating one of the local schools at our Bough Beech treatment works.

Did you know our Education Co-ordinator Jo Hedges visits around 70 schools every year teaching 7,350 pupils about water efficiency and the process our water goes through? Our Bough Beech school tours enable children to see first-hand the process of water treatment from chlorination, to screening, all the way to it coming out of the tap. Not only do we share the process but also include how we could save water. The children discuss how much water one person may use to that of a family and the lack of water in third world countries. For more information about our school tours and visits, check out our education page –




Did you know we have a lab based in our Redhill office? This is where we test the water from customers to check its quality.

Monday 13 March 

Today our focus is on our water samplers who visit our customers and take 1800 water samples per year! The team bring these water samples back to the lab at our office in Redhill for it to be tested.

Our Samplers also visit our treatment works and take samples to test our water before it is processed and distributed to customers. Every week they take around 31 samples from our storage reservoirs and water towers to ensure our water quality is at its best!

‘Our Water Quality Sampler Lucie Waller is out taking samples!’

Find out more tomorrow about how we are educating young people on the water process. #BSW17

Friday 10 March 

We distribute 160 million litres of water to 285,000 properties every day. This can easily rise to 260 million litres on a hot summers day.

Our Water Quality Science Manager Rob Baldry told us; “We speak to our customers about their water sample results and investigate any sample failures. This includes testing the taste, odour and any discolouration. We have so much going on in the lab, with the Samplers out speaking to customers and the scientists and chemists investigating how we can keep the quality of our water supply at its best.”

There is a growing demand for water each year because of an increase in both people and property. By 2040, the population in our supply area is forecast to increase by 155, 000!

Find out more about the water process next week for British Science Week. #BSW17


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