Assessed water charges are normally used when a customer has requested a water meter but can not have one fitted due to technical difficulties or there being an excessive cost associated with fitting the meter.
Water companies have different ways for determining assessed charges.
Some base the charges on the type of property you live in: Flat/Terrace, Semi Detached or Detached property.
Some use a flat charge based on the average household bill:
The water supplier will have a monitoring scheme running on some of the properties they supply which gives them the average usage in there area.
You can contact your water supplier and apply to join the monitoring scheme and may get you a reduction in your bill if you are selected to join.
Some use occupancy based charges so the bill will be based on the amount of people that live in the property.
Finally some charge based on an assessment of the customer's usage:
You will be asked how many showers,Baths,washing machine loads per week are used at the property.
The surface water drainage charges are based upon a banded annual charge determined by the property type i.e. detached, semi-detached or flat/terraced
If you have requested to have a water meter fitted at your property but could not have one fitted, contact your water supplier to discuss Assessed charges as an alternative.