PPC115 | Technical

Darron Pearce from BPCA member company, Rattraxs Pest Control, has over 30 years of industry experience in both pest control and drainage. He carries out surveys for insurance and mortgage companies, and domestic customers looking for rodent ingress from defective drainage.

We all deal with rats within properties. Sometimes, it’s easy: something obvious like a damaged air brick or a hole in a wall where a sink pipe once was. And then there are the calls where we are just left scratching our heads.

You’ve checked everything over and over... it can only be the drains, so you advise that a drainage company should carry out a specialist CCTV survey. Confident that you have carried out a full and thorough site inspection, you move on and let the drain people find the fault.

Then the customer calls a few days later to inform you that the drains are fine. They’re not happy that they still have rats and now they’ve spent extra on a needless survey. You return to scratching your head. Now, there are some very good and competent drainage surveyors out there – those who know what to look for and where to look for it. Then there are those who only see what the camera sees and, in many cases, the obvious is missed – although it’s only obvious if you know where to look!

Rats live in drains, that’s a fact. It is estimated that, on average, 80% of rat infestations within the home originate from drainage, be that from a defective drain, a dry line not capped off correctly when an extension was carried out, or drainage that has been altered to add extra utilities. In these cases, it is advised that a drainage company is contacted to carry out a full CCTV survey with a report to, hopefully, identify the defect and offer a solution.

Before we rush into expensive surveys, have we, as pest controllers, carried out our own survey regarding the drains? 

You don’t have to be a drainage specialist or have extensive knowledge of drainage. What you do need is a good pair of gloves and a willingness to lift a chamber lid!

Safety first

Put on gloves and ensure a safe working environment. Inform your customer that, as part of your inspection, you will be lifting manhole covers and inspection chambers within their boundary. Make sure pets and young children are safely within the property.

Lift and set aside the chamber lid, to allow the chamber to vent for a short while. The drainage we will largely come into contact with will naturally vent through soil vent pipes (SVPs) and breather pipes fastened to the property. Nonetheless, allow the chamber to vent, in case those pipes are non-existent or impaired in some way.

Health and safety are paramount. There are so many safety concerns regarding entering manholes so, in brief, just don’t.

Inspection chambers close to the property are the ones we are interested in. These are usually shallow, many less than one meter, and are relatively easy to inspect.

So, working from the top down...

The cover and frame

Have you ever thought of checking the customer’s drainage cover when you are called to a complaint about rats in the garden? If the cover is defective, old and rusty, or the supporting edges have given way, this is an open door to and from the sewer system. It’s always worth a look at the drain cover when rats are noticed above ground.

Check the underside of the frame where it meets the brickwork. Is it flush and secure? 

If the chamber is shallow enough for the rat to jump its height, rats will often squeeze between the frame or surround and brickwork. From here, they will burrow unnoticed as the excavated soil will get washed away in the wastewater flow.

I have never seen a correct or successful ‘add-on’ to a plastic inspection chamber. I would go as far as to say it’s impossible. If a builder thinks this is satisfactory when it can be seen, what is his work that can not be seen?

If you are inspecting a ‘poly’ or plastic inspection chamber, check to see that it has not warped and has kept its shape. If you have a round cover and frame meeting an oval chamber, the two will not match and will not be secure. Again, this is another area taken advantage of by rodents that often goes completely unnoticed.

“Where several channels enter the chamber, ensure that the areas between them are inspected. Quite often, there is little or no concrete in these areas...”

Chamber wall

Is it in a good state of repair? Have there been any alterations or add-ons where new pipework has been introduced into the chamber? If the customer has had an extension with a new toilet or utilities, builders will often bring in the new drainage at a shallower depth and break it in through the chamber wall.

This is common practice and not an issue, provided that the new drainage is secured and sealed correctly within the chamber wall.

All may look great from above, but not so good where you can not see. Mortar finishing may be incomplete under pipe entrances – an easy exit from the drains, excavation spoil will be washed away

Benching and channels

The benching within inspection chambers and manholes constructed of brick or concrete raising sections is usually constructed with concrete and shaped to secure the pipework entering and exiting.

After years of continuous flushing or water splashing, benching often deteriorates and collects wastewater and all the other delights we flush away. A regular food and water source for your common rat.

What starts as a collection point can soon turn into an area where rats will burrow. Again these areas are often overlooked. Where several channels enter the chamber, ensure that the areas between them are inspected. Quite often, there is little or no concrete in these areas, allowing rats to start their exit campaign.

Another area missed by drainage contractors and very often not inspected by us pest controllers is the back of toilet bowls, especially in a fitted bathroom or wc. If the customer has a downstairs toilet, it is critical to check. If the toilet is connected to the drainage by a flexi pipe, then this could be the entry point into the dwelling.

“An additional benefit is the potential to do right by your customer by saving them time and money, ”

Redundant lines

If you suspect you have an obvious point of entry into the dwelling from the manhole, drain ‘bungs’ can offer an immediate solution. It is vital to carry out a full flow test before fitting a bung. If in doubt, do not fit a bung but, in many cases, it’s the obvious way forward.

Non-return valves (NRVs)

If you suspect that there is a section of drainage allowing infestation, then an NRV could be an option, provided it is fitted in a private section of drainage. While I do use NRVs as a process of elimination, I try not to use them as a permanent fix.

If rat activity stops after fitting an NRV, a CCTV survey should be carried out to identify the defect and then a permanent solution be executed. After all, the defect could lead to more sinister issues like water loss, loss of structural integrity and subsidence. There is also the risk of the NRV failing and rats re-entering the property.

NRVs serve a purpose, but further investigation is advised.

Final thoughts

By incorporating simple drainage inspections into our site surveys, we could potentially solve the problem permanently and reduce our use of rodenticides, which would be better for the customer and the environment.

An additional benefit is the potential to do right by your customer by saving them time and money, and the benefit for you via a nominal increment in your fees.

A little bit of drain knowledge goes a long way, and no one will be more pleased with your new knowledge than your customers.