Vermin commonly enter your home through its drainage system, which is connected to the main sewage network. Almost every home has a running trap (U-bend) that collects wastewater in the bend to prevent it from entering the piping and into your drainage system.
However, this U-bend does not always operate efficiently because the rodding eye access leaves the pipe accessible for vermin to enter. A non-return valve or rat-blocker is a very cost-effective solution that we have installed many times for our clients in the Brighton area.