The number of rats in sewers is growing and increasingly this leads to more of our rodent situations being caused by rats ingressing into the property through the drainage. The cause could be something as simple as recent building work having left an uncapped drain. Alternatively it can be because a drain system has failed due to age. Typically on a job where possible we will always bait a drain to see if there is rodent activity. If it is suspected that rats are coming through the drainage system then a drain survey can be undertaken. This entails putting a camera up all areas of the drain system to locate any holes or other access points.
Evidence that there is rat activity in the drains can be from droppings left behind by a rat or soil physically in the manhole. Soil or stones can indicate that rats have pulled the debris into the drain while tunnelling out.
Once the problem has been identified there are different pest control solutions that can be applied. Often fitting a non-return valve solves the issue without major drain works being needed. The principal here is any rodent pests in the property leave pushing open the non-return valve. It is fundamentally a one way door so that they cannot then re-enter the property. It is important the non-return valve is fitted properly so that it does not get stuck either in the open or closed position. It may be a rat has found a fault in the manhole itself along the benching. In this instance it is advised to re-point the drain to stop access.
Although in these instances it is unlikely a rodent will find another way in we sometimes advise a non-return valve additionally to the works because we do know that rodents will try to gain entry through another way. Even if generations are killed of rats scent markings are left meaning further generations will try and gain entry. The drain camera is very useful as it can go very far along drains right to the end to see if chewing has occurred.
It may be surprising to hear that scratching in the loft is caused by something coming from a drain but once rodents enter a property they are extremely good at finding their way round usually using cavities as a way up and down the property. For example a rodent may be living in the loft space, feeding in the kitchen at night and gaining water from the drain to drink. When rats have the right environment with appropriate food and water provided this is when they will start mating and the numbers of rats grow in the property. This is why we advise to start pest control as soon as possible when rodent activity is noted so it does not have time to take hold.
Finally it is worth noting that both new and old properties can have this problem. Old properties because clay pipes may fail and crack. New properties because the drain pipes and connectors are made of plastic so if rats can get enough purchase for it to chew through entry to the fabric of the property is gained. If you have any questions about drainage surveys rats and mice in general or anything pest control related please do get in touch as we would be happy to help. Have a great day!