About storm overflows

Wastewater is exactly that.

Waste from your home or business, it is anything you put down your sink, bath, drains or toilets; it all ends up in our sewer network. That’s why only paper, pee and poo should go down the loo.

Storm overflows are an important part of our wastewater network because they protect customers’ homes and the environment.

They operate automatically as a relief system during heavy rain or storm conditions, or if the sewers are overwhelmed because of more water or blockages, and reduce the risk of flooding to streets, homes, and businesses. As the rainwater runs into and overwhelms the sewer network, the overflows release the storm water into our waterways. A small amount of wastewater from our network can be mixed into this overflow, but, due to the amount of rainwater, it is significantly diluted.

Once rainfall subsides, and levels in the sewer reduce, the system can carry the excess flow allowing the storm overflow to stop automatically. You will see more activity during wetter weather and less during drier weather.

Storm overflows usually work automatically due to the force of gravity. When the sewer, pumping station, or treatment facility reaches its limit or fills up, the overflow is triggered. However, in a few specific places, we use pumps to raise the flow and manage the release of excess water.

The storm overflows are permitted to discharge into the environment by the Environment Agency during rainfall or snow.

To see how storm overflows work – watch our storm overflow video (opens new window).

Outfalls from storm overflows are the pipes where these spills physically enter waterways or the sea.

Outfalls can be some distance away from storm overflows and sometimes there is more than one storm overflow connected to an outfall. We have made both outfall and storm overflow locations visible on our map.

When first opening the map the pins that you will see are outfalls. By using the zoom function you can see the outfalls and storm overflows that are connected to them.

This map shows our operating area, which stretches from the Scottish borders, down to North Yorkshire and from the North East coast across to Cumbria.

The pins indicate the location of our storm overflows and outfalls. The colours show, near to real-time, when they spill excess stormwater.

The map is automatically updated by our monitoring equipment located at the storm overflow. You can use the map to see if overflows are currently discharging into a watercourse, or the date and time of the last recorded discharge.

We have shown all the outfalls that are associated with our storm overflows on the live map.

These are the ones that have our monitoring equipment installed, which can send us information about discharges.

Surface water outfalls are not shown on our map because they only discharge rainwater. Highway drainage outfalls and private sewer outfalls are not shown on our map because they are owned by third parties.

Event Duration Monitors – or EDMs – are located throughout our wastewater network at all the points where spills are allowed to occur when there is too much wastewater due to excess rainfall, or blockages.

These monitors measure the levels of wastewater in our sewers at either two minute or 15 minute intervals and send that data to us either whenever a spill starts or stops, or once a day when there have been no spills.

This provides us with an almost real-time picture of spills should they occur. This data is also useful for the Environment Agency to monitor the performance of all water companies when it comes to storm overflow activity. These monitors provide us with vital insights to understand how our sewers and treatment works are performing, and more importantly, where improvements are needed.

The sewer system is designed to use overflow outlets when it is overwhelmed by rain.

The system is designed this way to manage water during intense weather, and when the overflow does happen, the released water is usually quite diluted due to the rain mixing in. It's a last resort, used when other measures can't handle the excess water, like during heavy rainfall or when there's a problem like a power cut or a blockage in the sewer pipes. These overflow points release a mix of rainwater and wastewater into rivers or the sea, but this is a safety measure to prevent streets, homes, and businesses from flooding.

Mostly.

Some storm overflows cover large geographical areas so there can be a delay from when the rainwater enters the network, to it discharging to the overflow point as it can take a few days for the rainwater to drain through the system. However, there can be a number of other reasons why you might see a spill, from storms and heavy rain to a blockage in the sewer pipes.

Unfortunately, yes.

Which is why we ask you to 'Bin The Wipe’ -  only flush pee, poo and paper down the toilet - and not to put anything else down the drains that could block our network. This all helps keep our sewers free-flowing and running at capacity. Blockages can also be caused by pouring fats and oils down sinks and can cause ‘fatbergs’ that are costly to remove.

Along with helping to stop the blockages, there are other things you can do to help the environment. For example, using a water meter will let you know how much water you are using and can reduce the amount of wastewater produced as knowing how much water you are using helps you to use water more wisely. Water butts also ease the pressure on the volume of water entering the sewer network and therefore the potential for spills. Gardens are also perfect for soaking up the rain, unlike paving, tarmac, and concrete, which can increase the amount of rainwater runoff. You can help by keeping paving to a minimum, leaving space in your garden for plants, and allowing driveways to drain into borders.

Our monitoring system alerts us when the level in the storm overflow is about to discharge, this is like an early warning.

We aim to attend site within two hours to deal with any issues or blockages we find, 24 hours a day, seven days a week.

Most of the time we can clear the blockage, return the storm overflow to normal operation and prevent a discharge to the environment.

There are times when the discharge has happened before we arrive on site and in these cases, we make sure the blockage is cleared and the environment is returned to its normal condition. We also report these incidents to the Environment Agency.

For some storm overflows, it can be difficult to always attend within two hours due to the location of the overflow. We will always get there as soon as possible.

In Autumn 2023 we unveiled our new draft Business Plan for 2025-30 (PDF, 1,244KB).

In this plan we want to invest more than £1.7bn to improve the environment, more than ten times the amount we currently spend.

Customers have told us that investment in storm overflows is important and we have ambitious plans to tackle this.

For a long time, storm overflows have been set up this way to prevent homes and businesses from flooding during intense rain. To change this, we would have to make major changes to the sewer system. This involves using nature-based and sustainable drainage solutions like storage ponds that are better for the environment.

We have invested heavily and worked hard on our track record for protecting and enhancing the environment, with some of the highest standards for bathing water quality, the cleanest rivers, and the lowest levels of pollution in England and Wales. Through our Business Plan, we will eliminate serious pollution events, and deliver a 30% reduction in all pollution incidents by reducing the number of spills from storm overflows by about a fifth, focusing on the most vulnerable locations.

We acknowledge that we need to move faster on spills to the environment. We understand the scale of transformation that will be required and are determined to deliver our most ambitious plan yet.

In the North East, we have some of the lowest levels of pollution and some of the cleanest rivers and beaches in the country.

32 out of 34 of our coastal bathing waters are classified as Excellent or Good and two of our catchments, Northumbrian Rivers and the Solway, have the highest proportion of water bodies by surface area meeting good ecological status in England and Wales. Pollution incidents associated with storm overflows have fallen significantly through our industry-leading monitoring and pollution management approach.

Our Pollution Incident Reduction Plan (opens new window) sets out our plan to meet our ambitious goal to have zero pollutions because of our assets and operations. This continues a significant downward trajectory over the last decade - reducing serious pollutions from 11 in 2011 to just one in 2021, and less serious pollutions from 189 in 2012 to 60 in 2022. Our targets agreed with our regulator, Ofwat, were 69 for 2022, 67 for 2023 and 58 for 2024.

To further enhance the health of our waterways we use nature-based solutions where possible. Working in partnership with The Rivers Trust, we set up The North East Catchments Hub (NECH) in April 2022. We have invested around £300,000 so far in NECH, which has brought resources and expertise into the region to support development of our business plan for 2025-30. The NECH has been working closely with us, other catchment partnerships and environmental groups to identify opportunities for catchment and nature-based solutions. Five workshops were held in summer 2022. Eight schemes were then developed and have been put forward for inclusion in our Business Plan for 2025-30.

The impact of each discharge will vary depending on the location and duration of the discharge.

Our storm overflows are permitted to discharge during wet weather by the Environment Agency considering the requirements of the receiving watercourse. Our event duration monitoring equipment can inform us when a discharge is happening during dry weather, due to a blockage for example, and in these cases we self-report discharges to the Environment Agency who will assess the impact any discharges have on the environment.

Our storm discharge map gives information on the status of our storm overflows. It shouldn't be used to determine water quality or if it’s safe to enter the water. This is because many different factors affect the water quality and safety of our rivers.

If you'd like to find out more about river water quality, and water quality sampling in your area, contact the Environment Agency.

No. Many different factors affect the water quality and safety of our rivers and coastal waters.

It all depends on the surrounding area. For instance, if there is farmland nearby, agricultural land run-off will impact on the health of the river, also any run-off from highway drainage systems is likely to enter the watercourse unrelated to whether a storm overflow is operating.

Surface water sewer

Surface water drainage happens when rainwater falls on a property and drains away. These pipes don’t always flow, especially after a long dry period, because they carry rainwater away from roads, houses, and built-up areas. The rainwater should be clean but sometimes it can contain pollution spilled onto a road or tipped down a drain. Sometimes waste pipes from houses are wrongly connected into surface water sewers and that might lead to wastewater going straight into the river instead of going to a wastewater treatment works.

Culvert

A culverted watercourse (or culvert) is a watercourse that has been channelled through a pipe so that it can be built over. Culverts flow 24 hours a day and they should be clean, but sometimes waste pipes from houses are wrongly connected into surface water sewers or culverts and that might lead to wastewater going straight into the river instead of going to a wastewater treatment works.

There are some pipes that we call wastewater treatment works outfalls.

These pipes flow 24 hours a day and they return wastewater after it has been treated at a wastewater treatment works. The water must meet strict standards set by our regulators. You might notice a little foam in the river near the outfall because air that goes into the water during the treatment process can be released as bubbles when it joins the watercourse.

When it rains, the excess surface water finds its way to the sewerage network.

Heavy or continued rain can risk overwhelming it. Where the sewer network covers a large area, it takes a while for the water to drain through the sewer network and for storm tanks to be emptied for treatment. For some of our storm overflows that serve a large geographical area, the overflow can continue after the rainfall has stopped.

We work hard every day to make sure wastewater is properly treated before it's discharged into our rivers and streams. We use EDM data (opens new window), along with other tools and information, to identify and respond to problems.

We provide data to the Environment Agency around spills into watercourses.

The EA is responsible for advising if it is safe to enter a watercourse as there are other factors that affect water quality that aren’t our responsibility.

For more info you can take a look at Swimfo (opens new window) to find the latest bathing water quality guidance. 

Please remember to consider all the safety factors when wild swimming in rivers and other watercourses.

Our map  indicates our storm overflow activity, not the other potential hazards in watercourses. With so many different factors affecting the water quality and safety of our watercourses, our data should not be used by itself to determine if it’s safe to enter the water.

Look at Swimfo (opens new window) or Catchment Data Explorer (opens new window) to find the latest bathing water quality guidance. Bathing water quality alerts are also available on the Surfers Against Sewage Safer Seas and Rivers Service (SSRS) app.

The EA is responsible for testing river water quality.

If we think a watercourse has been polluted, we'll test the water quality and work with the EA to investigate.

We measure the frequency and duration of storm overflow operations using Event Duration Monitors (opens new window) and have reported on this since 2020.

We'll take a monitor offline to investigate if:

• It stops communicating with our systems.
• Produces inaccurate data.
• We identify an issue with the device.

We aim to get offline monitors working again as soon as we can. This may take some time if the installation location is difficult to get to, for example, in manholes on busy roads.

Monitors may also be offline if significant investment works is taking place on-site, for example, upgrading one of our sewage treatment works.

Some offline monitors do still record discharge activity, but the data isn't reliable.

While a monitor is offline, we won't display any further details about it. The monitor could be broken and unable to record active discharges. Or it could falsely indicate active discharges when there aren't any. We take the monitor offline to investigate exactly what's happened and aim to get it working again as soon as we can.

The watercourse may include other inputs such as highway drainage, surface water and culverted watercourses.

EDM monitors are normally located at the point of the overflow so the performance of each overflow can be monitored which helps to target required improvements.

The pins should only overlap when you are zoomed out on the map due to the size of the pins and the distance between them.

When you use the zoom function the pins will then indicate the location of the overflows and outfalls and will not overlap. You will be able to see all the information for the overflow and outfall in the pop-up box. If you think anything isn’t working on the map as it should, please let us know by calling us on

0345 717 1100.

Not all pumping stations have overflows and we have installed monitors on our storm overflows, so only the pumping stations that discharge in storm conditions will have EDM installed.

There will be some locations where sewage escapes due to a breakdown, power failure or blockage. These locations may include pumping stations, which are not currently monitored. We'll be adding more locations to the portal as and when EDM monitors are installed.

Where sewage treatment works are permitted to discharge storm water, they are shown on our live map.

Some of our sewage treatment works are designed to treat all the flow which arrives at the site. These don't have the ability to discharge storm sewage but are permitted to discharge treated sewage. Some of our smaller treatment works discharge flow to ground, for example from a septic tank, not into rivers.