Visit What's In Your Backyard (WIYBY), a tool from the Environment Agency, to determine if your farm drains into a drinking water protected area safeguard zone. WIYBY should be consulted regularly to ascertain which, if any, pesticides are causing concerns in your area so that you can take steps to help address these.
To use WIYBY for this purpose enter your location and check the boxes for surface water protection zones and groundwater protection zones.
You can find out more about using WIYBY by reading a VI leaflet on WIYBY.
You can also visit the EA's pages on WIYBY.