What Causes a Clogged Manhole and How To Fix It

If you have a clogged manhole, it’s one of the first visible signs of deeper drainage issues. Without prompt action, you could find your property flooded, filled with unpleasant odours, and some serious health risks will present themselves.

There could be a multitude of causes for the blockage, from the build-up of fats to tree root ingress and seasonal debris. While basic intervention may help, some blockages will likely require professional inspection to determine the true cause and prevent the issue from happening again.

At Express Drainage Surveys, this month, we’re looking at the topic of clogged manholes more closely to help homeowners and businesses out.

What is a manhole and why is it so important?

Let’s begin by outlining what a manhole actually is. It is essentially a covered access point to the underground drainage or sewer system. They allow easy inspection, maintenance and emergency intervention within drains. Here in the UK, they can be for both foul and surface water drainage networks alike, and you’ll be able to spot them because of their large metal covers.

Typically, manholes are found at the junction point in the drainage network. This is where the pipework changes direction, and it can be found anywhere in your garden or on your driveway, as well as on the pavements and roads.

Manholes are important because they sit at what is known as a collection point. That means a blockage within the manhole can cause issues for a number of your property’s key outlets, as well as those of your neighbours.

Common causes of a clogged manhole

Working out what is actually clogging your manhole is probably the first step towards getting the right help. But whether the blockage has developed quickly or over a sustained period of time, it’s likely to be one of these common culprits:

Fat, oil and grease build-up: A frequent nightmare from kitchens, with fat, oil and grease solidifying once they cool, clogging your pipes and potentially creating a blockage at a manhole.
Wet wipes and non-flushable items: Regardless of what many brands claim, most “flushable” products do not break down sufficiently once flushed. This leads to wipes, sanitary products and nappies being the culprit for a blocked manhole.
Leaves, mud and seasonal debris: Throughout autumn and winter, leaves and surface debris can all get washed into drains. Once it builds up to a certain point, it tends to accumulate faster than it can be washed away, eventually blocking the system.
Heavy rainfall: Prolonged or super intense rainfall has been known to overwhelm drainage systems, and a symptom of this is that manholes then tend to flood when it becomes too much.
Tree root ingress: With tree roots naturally seeking out moisture, drainage pipes can be a target. Small cracks let roots into your drains before eventually expanding and blocking water flow through the manhole.
Pipe collapse: Any shifting earth around pipes or repeated pressure over them can cause leaks, collapses and misaligned joints, which eventually means water flowing into the manhole has nowhere else to go but up.

Signs that your manhole is blocked

If you spot the early warning signs of a blocked manhole, you should never ignore them. The sooner you act, the better chance you have of rectifying things before further damage and havoc can occur. Here are the common signs to look out for:

Slower-draining sinks, toilets, baths and showers
A foul odour from around your external drains or manhole
Your pipes inside the property gurgle when using water
You can see the water level is gradually rising over time inside the manhole chamber
The area around your manhole floods after rainfall

You could seriously reduce the amount of damage and cost associated with these issues if you recognise the signs early and seek professional drainage help.

Public vs private manholes: Who is responsible?

You may be wondering who is responsible for a blocked manhole in the UK, and the answer comes down to whether it serves a private drain, a shared lateral drain or a public sewer.

As a rule of thumb, you, as the property owner, are responsible for any drainage issues for drains within your boundary and that serve your property. Lateral drains and shared drains are now often the responsibility of the local water authority in your area.

However, it may not be that simple to determine where the actual issues lie, which is why a professional drainage survey is recommended to identify the blockage location. This can also show which properties are affected and who may be responsible for the repairs, helping to settle any disputes.

What to do if you suspect your manhole is blocked

If you suspect that your manhole is blocked, always ensure you operate with a safety-first attitude. This means only lifting the manhole cover if absolutely necessary. This is because the covers can be heavy and the chambers may contain contaminated water.

You should keep pets and children away at all times during your inspection of the manhole. This will allow you to identify whether the water levels appear to be unusually high, signalling the need for the services of a professional.

If the wastewater is already overflowing, you should stop using your internal plumbing immediately and engage with a local drainage company you can trust – like our team at Express Drainage Surveys.

When to call Express Drainage Surveys

When your manhole is blocked, it can have a wider impact on your property. Should you notice any of the signs we’ve outlined in this article, you can reach out to us for professional drainage support. We offer a full range of drainage services to help pinpoint the location and cause of problems in your pipework before recommending the right course of action.

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