Rats are capable of travelling through underground drains and sewer networks, including pipes connected to residential properties. Their presence in a sewer is not necessarily a sign that anything is wrong with the drainage system.
Problems arise when damaged pipework, defective inspection chambers or poorly sealed connections allow rats to leave the drainage system and gain access beneath a property, into wall cavities or through gaps around plumbing installations.
Where rats are repeatedly appearing inside a building, the drainage system may be one possible route of entry worth investigating.
Can Rats Enter a House Through the Drains?
Yes. Rats can travel through foul drainage systems and, in certain circumstances, find their way into buildings through damaged or incorrectly connected pipework.
An intact drainage system should prevent rats from escaping into the surrounding building structure. However, an opening in a pipe or an unsealed connection can provide a route into spaces beneath floors, behind walls or around the foundations.
Rats may also access properties through damaged toilet connections, redundant drainage branches and openings around pipe penetrations.
Importantly, finding rats inside a property does not automatically mean they have entered through the drains. Gaps around doors, ventilation openings and other structural defects can provide alternative routes.
Signs Rats May Be Entering Through the Drainage System
There is no single symptom that confirms rats are entering through a drain. However, certain circumstances can make a drainage-related entry point worth investigating.
- Repeated rat activity despite pest control: Rats continue appearing after previous treatment, suggesting an access route may remain open.
- Scratching beneath floors or behind walls: Activity concentrated around bathrooms, kitchens or areas containing drainage pipework may warrant further investigation.
- Evidence of rats around toilet connections: Droppings, gnaw marks or other signs of activity near concealed plumbing may indicate a possible access point.
- Activity following building work: Rat problems that begin after an extension, bathroom alteration or drainage modification may be associated with a redundant or incorrectly sealed pipe.
- Damaged inspection chambers or exposed drainage connections: Visible openings in drainage infrastructure may provide routes out of the system.
These signs are not conclusive. Establishing whether the drainage system is responsible normally requires a broader inspection of the property and its potential entry points.
Common Drainage Defects That Allow Rats to Escape
Several types of drainage defects can create potential access routes from the sewer system.
Broken or Displaced Drain Pipes
Cracked, fractured or displaced underground pipes can create openings between the drainage system and surrounding ground.
Where these openings are sufficiently large, rats may be able to leave the pipe and burrow through nearby soil. Whether they can subsequently enter the property depends on the location of the defect and the surrounding building structure.
Unsealed or Redundant Drainage Connections
Older properties and buildings that have undergone extensions or renovations may contain disused drainage connections.
If an old pipe or branch connection has been disconnected but not properly sealed, it can provide a route from an active drain into an underground void or other part of the building.
These defects may remain hidden for years, particularly where the original drainage layout has been altered.
Damaged Inspection Chambers
Inspection chambers can develop defects in their brickwork, pipe connections or internal benching.
Deteriorated sections may create openings into the surrounding ground. In some cases, rats can exploit these defects to burrow away from the drainage system.
Defective Toilet and Soil Pipe Connections
Rats can sometimes gain access through damaged or poorly sealed connections around toilets and soil pipes.
Flexible WC connectors, concealed pipework and inadequately sealed openings are potential points of concern, particularly when rodent activity is concentrated around bathrooms.
Will Pest Control Alone Solve the Problem?
Pest control and drainage repairs address different aspects of a rat infestation.
A pest control specialist can investigate rodent activity, identify potential access routes and recommend suitable treatment and proofing measures.
Where the drainage system is found to be contributing to the problem, the underlying defect also needs to be addressed. Otherwise, an opening may remain available for further rats to use.
However, drainage defects should not automatically be assumed to be responsible. A thorough investigation should consider other potential entry points before recommending underground drainage work.
How Can a CCTV Drain Survey Help?
When there is evidence suggesting rats may be entering through underground drainage, a CCTV drain survey can help investigate the condition of accessible pipework.
A camera is passed through the drainage system to look for defects such as:
- Fractured or broken drainage pipes.
- Displaced joints and openings in the pipework.
- Unsealed or redundant branch connections.
- Damage around inspection chambers and pipe connections.
- Other structural defects that could provide a potential route out of the drainage system.
A CCTV survey can identify possible access points, but it cannot always establish the exact route rats are taking into a building. Further investigation may be needed to connect a drainage defect with the location of rodent activity.
For this reason, CCTV inspection is most useful when there is a reasonable suspicion of a drainage-related problem, rather than as an automatic response to any rat sighting.
How Are Rat Entry Points in Drains Repaired?
The appropriate repair depends on the location, severity and type of drainage defect identified.
Some damaged pipes can be repaired using localised patch repairs or drain lining, provided the existing pipe remains suitable for the chosen method.
More substantial damage, severely displaced pipework or defective connections may require excavation and replacement. Redundant drainage branches may need to be properly sealed or disconnected.
In some situations, a purpose-designed rat blocker may be considered, although these devices must be suitable for the drainage arrangement, installed correctly and maintained to avoid obstructing wastewater flow. They do not replace the need to repair known structural defects.
Our drain repair cost guide explains the factors that can influence the cost of repairing damaged underground pipework.
What Should You Do if You Suspect Rats Are Coming Through the Drains?
If rats are appearing inside your property, the first step is to investigate the source of the infestation. A pest control specialist can assess rodent activity and identify likely entry points.
Where evidence suggests the drainage system may be involved, inspecting the underground pipework can help establish whether any defects require attention.
Drain Division can investigate suspected drainage defects using CCTV survey equipment and recommend suitable repairs where problems are identified.
To discuss a possible drainage-related rat problem, call 0333 200 1623 or visit our contact page.