Lilly pond groundwater
Calendar 10 November, 2023 (Updated 13 November, 2023)

Source Protection Zones (SPZ): A Guide

Approximately one-third of our tap water in the UK comes from groundwater sources including wells, boreholes and springs; in some parts, this rises to as much as 80%.

Groundwater also feeds into rivers and other watercourses, providing habitats for aquatic wildlife.

It is therefore of utmost importance that groundwater sources are protected from pollution and to do this, the Environment Agency has defined categories for source protection zones (SPZs) that indicate the level of contamination risk in each zone. Potential sources of contamination include underground fuel storage tanks and septic tank soakaways.

What are the SPZ Categories?

Source protection zones are divided into categories, based on models that estimate two statistics:

  • the length of time it will take pollutants to travel through groundwater to the point where the water is extracted (the water source)
  • the area around the water source that needs to be protected against groundwater pollution.

SPZ1 – Inner Zone

The area immediately surrounding the water source is known as the inner zone. In this zone, pollutants are estimated to take 50 days to reach the water source and potential sources of pollutants are prohibited within a default minimum radius of 50 metres.

SPZ2 – Outer Zone

The outer zone is the area where it is estimated pollutants will take 400 days to reach the water source. The outer zone prohibits potential sources of pollutants within a minimum radius of 250-500 metres, depending on the volume of water that is to be extracted from the source.

SPZ3 – Total Catchment

The total catchment zone is the complete area that feeds the water source and may extend across a considerable distance.

1c, 2c & 3c – Extended Zones beneath protective cover

Some zones have been extended to include areas where protective geology cover such as clay is present. Underground activities such as deep drilling can potentially form pathways for pollutants to enter the groundwater.

SPZ4 – Zones of Special Interest

This category is reserved for zones where local conditions require additional protection.

When do I need to find out whether I’m in an SPZ?

There are several reasons why you may need to know whether your property or a property you are developing is in an SPZ. You may simply be interested in the quality of your drinking water, but if you are extracting water from a ground source, installing certain drainage systems or conducting certain activities, knowing whether your property sits within an SPZ is essential.

If you are considering extracting groundwater for domestic drinking water or commercial bottling, an SPZ check will confirm whether the water will be of sufficient quality.

On the other hand, if you are considering installing a septic tank or soakaway, carrying out activities such as spreading animal waste on agricultural land, or constructing a chemical or fuel storage or distribution facility, you need to confirm that you aren’t falling foul of an SPZ.

Where can I find out if I’m in an SPZ?

The simplest way to find out whether your property falls within an SPZ is to use the MagicMap tool from the UK’s Environment Agency.

  • Once you have opened the tool, navigate the table of contents on the left-hand side as follows:

Designations/Land-based designations/Non-statutory

  • Tick the box next to Source protection zones merged (England)
  • Enter your postcode in the Search box at the top-left of the screen
  • Choose your map scale from the drop-down list in the top-right of the screen (you can also scroll in and out on the map to change the scale)
  • Use the slider bar underneath the ‘Designations’ subheading in the table of contents to increase the transparency of the colour overlays and reveal the map behind them.


We hope you have found this information helpful and interesting. If you have any further questions you are always welcome to call the friendly team of drainage experts at Drainfast on 01420 555600 or email [email protected]

Also, look out for more articles in our ongoing series of blog posts, bringing you useful information, insights, guides and tips on all things drainage!

Vicki James Drainfast Team Portrait

Written by
Vicki James

Sales & Marketing Coordinator

Vicki is a vital part of the marketing team; from reporting to copywriting, she ensures we complete projects on time.

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