The Water supply company's in the UK will by default charge you for the run off of rain water.
This is not on.
Most modern property's have a soak away for rain water.
This is from the southern water web site.
"Southern Water's wastewater
standing charge on properties connected to the public sewers includes an amount for the disposal of rainwater run-off from the roof of your home and other paved areas.
In some cases there may be no connection to the public sewerage system because the downpipes may go into a soakaway. If so, you are able to claim a rebate from the current charging year onwards.
This is currently £22.00* a year for domestic customers.
Once your claim has been agreed you will automatically receive the rebate each year, although it cannot be backdated to earlier years"
Please check
https://www.southernwater.co.uk/pdfs...r_Domestic.pdf
At best this will save you £22 if you claim or more.
Please check your water bill.
If you are charged for surface water check the conditions in the above link (with your water supplier) and make your claim.
How long has this been going on?