A natural cycle threatened by climate change

Everything we do is reliant on the natural Water Cycle. Rain is what allows us to sustainably operate.

Rain falls into rivers, which then flow into our reservoirs, keeping them full.

If it doesn’t rain, rivers get low. Less water is collected into the reservoirs, and their levels start to drop. Meaning there is less water available in the environment for us to take for treatment.

In the past, the South West has had very reliable rainfall. However, climate change is altering that.

We’re having to adjust the way we operate to look outside our traditional methods of water treatment, to make sure we always have enough supply to meet demand.

Making water drinkable

Water treatment starts long before the water reaches the treatment works. If raw water sources are fit and healthy, it makes our job of cleaning it a lot easier. There are many stages of treatment that water goes through before we're happy enough to send it to your tap.

Man cleaning river
Water treatment process

Raw water quality

We call water in rivers and reservoirs ‘raw’ water. Farming practices, soil runoff, industrial processes, and sewage pollutions all affect the quality of this water. If the quality is bad, more energy is needed to treat the water at our works. That’s why we do a huge amount of work as part of our Upstream Thinking programme to safe-guard our rivers and reservoirs.
Our water resources
water abstraction
Water treatment process


Taking water out of the environment is strictly controlled. We have to take enough to meet demand, whilst keeping enough in the environment to maintain aquatic habitats and support the wildlife that also relies on the rivers. The water is put through screens that remove large debris like branches and leaves and stop any wildlife from entering the treatment works.
Settling water treatment
Water treatment process


Once water enters our treatment works, it’s immediately mixed with a solution that helps bunch all the remaining solid debris like mud and grit together. The mixed water then flows into settling tanks. The nasty stuff sinks to the bottom of these tanks and the cleaner water on top moves to the next stage of treatment.
GAC charcoal
Water treatment process


The water is filtered twice. First through sand to remove any micro-organisms that are still present in the water. Then it’s filtered through Granulated Activated Carbon (GAC) that removes tiny bacteria. Did you know: GAC is full of holes that trap the bacteria inside. Just 1 gram of GAC has a surface area of 1000 square meters!

Turquoise coloured pipes
Water treatment process


By the time the water has been filtered, it’s very clean. We use a small amount of chlorine to completely disinfect it before it enters the pipes.

Water of the future

There are many exciting innovations happening in water treatment every year. We're at the forefront of this progress in the UK, having built its very first ceramic membrane treatment works in 2021.

What makes Mayflower different?

Our Plymouth water treatment works, Mayflower, is the first of its kind in the country. Instead of using the traditional sand and carbon filters, it uses ceramic membrane technology.

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Sourcing more water

We've accelerated our plans to find and develop more water resources. From new raw water reservoirs to potential for desalination plants, we have a lot in the pipeline.

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How you can protect our water's future

Providing 1.8 million people with water is a balancing act of keeping a supply going whilst taking water from an environment that has less and less in it because of climate change. That's why it's important to be aware of your water use, and save where you can. Being water efficient isn't about not using water, but about only using the water you need. 

Water is Precious

Every drop you save is precious and makes a huge difference to our rivers and reservoirs, keeping them healthy places for wildlife to live.

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