Inflow and Infiltration Monitoring Project (IIM)
Welsh Water is delivering a major Sewer Level Monitoring Project, which will see over 10,000 sewer level monitors installed across Wales.
This important work will help us better understand how our wastewater network performs and where improvements are needed.
The project is currently underway, with completion aimed for March 2027.
In some locations, we may need access to manholes located on private property where these provide the most suitable monitoring points.
What do the monitors do?
The monitors measure how sewer levels change during rainfall, seasonal variations, and other conditions. This information helps us to:
- Identify inflow and infiltration entering the network
- Improve system performance
- Reduce the risk of flooding and storm overflows
- Protect the environment and improve long-term network resilience
Important: These devices are not flow meters and do not measure or record water usage at individual properties.
What work will take place?
We will install small, battery-powered monitors inside selected sewer chambers. The equipment is installed securely within the chamber. Installation is quick, quiet, and typically completed within minutes. There is no impact on your wastewater services.
Where possible, we avoid working on private land. However, where access is required, customers will be contacted in advance and work will be carried out as unobtrusively as possible.
What this means for you
As a Welsh Water customer, you can expect:
- No action required – the monitors operate independently
- Minimal disruption – installations are fast and unobtrusive
- Discreet equipment – monitors are silent and not visible
- Respect for your property – access is carefully managed and clearly communicated
Find out more
If you have any questions, Welsh Water Customer Services will be happy to help.