Environment Agency - logo Bathing Water Quality

Bathing Water Quality

The Environment Agency takes up to twenty water samples at each of England’s designated bathing waters during the bathing water season between May and September each year. A classification for each bathing water is calculated annually based on samples from the previous four years. These classifications are, from best to worst:

  • excellent – the highest cleanest seas
  • good – generally good water quality
  • sufficient – the water meets minimum standards
  • poor – the water has not met the new minimum standards. Work is planned to improve bathing waters not yet reaching Sufficient

A sample tells us the quality of the water at that specific time, but water can change even over the course of one day. In each sample we test for bacteria that indicate whether there is faecal matter in the water. The bacteria we test for are:

When more of these bacteria are present in a bathing water there are greater risks to bathers' health. The standards we use are specified in the Bathing Water Directive and are based on World Health Organisation research which recorded the incidence of gastrointestinal disease (stomach upsets) in people bathing in waters of differing bacterial concentrations.

Water quality can change over time, even in the course of one day. This may be due to:

  • Heavy rain or tides washing pollution into the water that flows into a bathing water from the surrounding catchment. Daily Pollution Risk Forecasts (PRF) alert users to this possibility for many bathing waters.
  • On rare occasions abnormal situations can occur which may affect water quality. For example a pollution incident.

Both of these kinds of water quality warnings are shown on the main map on the home page, profile pages for individual bathing waters, and the compare bathing waters page. PRFs are indicated by a warning triangle icon Warning triangle for poor water quality and abnormal situations by a warning circle icon Warning circle for abnormal situations.

Some bathing waters can be affected by Combined Sewer Overflows (CSO). About 70% of the sewers in England are combined systems. This means they collect runoff as well as sewage and wastewater from homes and businesses. The CSOs act as a safety valve during heavy rainfall. Unless these controlled discharges into local watercourses are permitted, there is a risk that sewage could flood homes and businesses following heavy rain overwhelming sewers.

At present this website does not provide alerts for CSO discharge. However we support the voluntary CSO alerts scheme set up by Surfers Against Sewage and water companies. More information can be found on the Safer Seas Service website.

Water Quality Assessments

Designated bathing waters in England now have tougher water quality targets to achieve; the new standards are approximately twice as strict as they were prior to 2015.

The assessment process is based on the Bathing Water Directive, which was fully implemented into English law on the 24 March 2015. It replaces the old 1976 directive and regulations.

From the end of the 2015 bathing water season all designated bathing waters will be classified as excellent, good, sufficient or poor. The classifications are based on a detailed statistical analysis of the sample measurements taken over a four year period. If a step change in quality has occurred because of an improvement action such as new sewerage infrastructure, only data collected since the action will be assessed.

The analysis groups bathing waters into classifications based on the probability that most of the time concentrations of Escherichia coli (EC) or Intestinal enterococci (IE) will be below classification thresholds (95% or 90% probability depending on the classification – see below). The criteria for coastal bathing waters and inland bathing waters are different. The thresholds for classifications are as follows:

Classification Thresholds Confidence level
Coastal Bathing Waters
Excellent EC: ≤250 cfu/100ml ; IE: ≤100 cfu/100ml 95th percentile
Good EC: ≤500 cfu/100ml ; IE: ≤200 cfu/100ml 95th percentile
Sufficient EC: ≤500 cfu/100ml ; IE: ≤185 cfu/100ml 90th percentile
Poor means that the values are worse than the sufficient
Inland Bathing Waters
Excellent EC: ≤500 cfu/100ml ; IE: ≤200 cfu/100ml 95th percentile
Good EC: ≤1000 cfu/100ml ; IE: ≤400 cfu/100ml 95th percentile
Sufficient EC: ≤900 cfu/100ml ; IE: ≤330 cfu/100ml 90th percentile
Poor means that the values are worse than the sufficient
Key EC: Escherichia coli, IE: Intestinal enterococci, cfu: Colony Forming Units

 

For planning purposes the Environment Agency uses unofficial classifications based on these standards for samples collected during years before 2015. These classifications use data collected using different analytical methods for data prior to 2012 and are therefore approximations of the class that the bathing water would have achieved if the new bathing water quality standards had been in force.

These classifications are included on this website to show the history of water quality at each bathing water and are marked with an p icon. The official classifications before 2015 are based on the old standards and can be found here or on the water quality data pages of this application. The first official classification under these new standards will be published towards the end of 2015, when there is a full four-year dataset became available.

The use of standardised symbols for the four classes, which all countries in the EU have to use at bathing waters across Europe, will helps people make informed choices on where to swim when home and abroad. The symbols are used on this site and are as follows:
Symbol for excellent bathing water quality Symbol for good bathing water quality Symbol for sufficient bathing water quality Symbol for poor bathing water quality

Symbol for advice against bathing If water is classified as poor, then the symbol for "poor" together with a sign showing advice against bathing must be displayed in the following year. A sign displaying a "poor" classification and advice against bathing does not mean bathing is banned or that a beach is closed, beaches remain open for people to enjoy.

Short term pollution

Short term pollution (STP) is bacterial pollution that occurs at a bathing water and is not expected to last for more than 72 hours. Management actions to deal with STP are designed to help protect the public from predictable pollution of short duration at a bathing water. Compliance samples taken during events which are defined as STP may be removed from the compliance dataset.

The Environment Agency issues pollution risk forecasts (PRF) at bathing waters where water quality is known to be reduced after heavy rainfall. PRF warnings identify where there is an increased risk of short term pollution due to run-off from heavy rainfall. STP events are those STPs which have warning signs displayed in the vicinity of the bathing water when a pollution risk warning is issued. They coincide with a routine water sample and an additional end sample has to be collected by the Environment Agency after the STP event to confirm its end. This end sample cannot be used for classifications.

Removing samples from the compliance dataset can only take place if they were collected during an STP event, and only up to 15% of samples used in the classification data may be removed over the four year period. This discounting assessment is made at the end of each monitoring season and is shown in the data by the discounted field.