Plumbing

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Oh My Leak! Part Two: How to Identify External Causes of Leaks Around Your Home

19th December 2025

Not all leaks begin inside the home. Many can start outside and slowly make their way indoors, often confusing homeowners who assume the issue lies with plumbing or heating systems. External leaks can cause just as much damage as internal ones, and often take longer to spot, so it can help to understand the common external sources so that you can react quickly and prevent long-term problems.

Check the roof

One of the most frequent culprits is a damaged or ageing roof. Missing or broken tiles, cracked underfelt and deteriorated flashing around chimneys or skylights all allow rainwater to creep into loft spaces and upper walls. The water may travel along rafters before appearing as a stain on a bedroom ceiling, making the true source hard to detect. Heavy storms often worsen existing vulnerabilities, so if you notice damp patches after bad weather, a roof inspection is a sensible first step.

Don’t forget gutters and downpipes

Blocked or broken gutters are another major cause of water ingress. When gutters overflow, water spills down the walls and eventually seeps through brickwork, especially in older properties. Downpipes that have become detached or cracked also direct water where it shouldn’t go. A simple visual check during or after rainfall can reveal whether your guttering is coping or spilling over.

The problem may not be above the ground…

Sometimes the problem originates underground. Damaged external pipes, including water board mains or supply lines, can saturate soil and foundations. This moisture can then make its way into basements, lower walls or floor levels. Signs of this include damp patches that appear without any rain, unusually wet soil near the property or unexplained drops in water pressure. If you suspect a mains leak, it’s important to contact your local water board, as they are usually responsible for repairs outside your property boundary.

Surface water drainage issues can also cause external damp. If the ground slopes towards your house or drains are blocked, water can pool and eventually penetrate through walls or below-floor voids. Persistent damp in ground-floor rooms can often be traced back to this kind of problem.

When dealing with external leak sources, safety and accuracy are essential. Roof work and underground pipe repairs should only be handled by qualified professionals. A reviewed and trusted roofer, drainage engineer or plumber can diagnose the issue properly and carry out repairs before further damage occurs.

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Looking for more plumbing advice?

Find clear, practical answers to common plumbing questions, helping homeowners understand everyday issues, know what checks they can carry out safely, and when it is best to contact a qualified professional.

What should I do if I have a blocked drain or sink?

Start with a plunger - create a good seal and use firm, steady pressure. For a kitchen sink blocked with grease, bicarbonate of soda followed by vinegar can help. If that's not shifting it, a drain snake reaches further down the pipe. Go easy on chemical drain cleaners as they can damage older pipes and rarely sort the root cause. If the blockage keeps coming back, affects more than one outlet, or you're getting unpleasant smells, call a plumber rather than trying to patch up the problem.
How can I tell if I have a hidden water leak?

The most obvious clue is a water bill that's gone up without any change in your usage. Beyond that, listen out for running water when everything's turned off, and watch for damp patches on walls or ceilings nowhere near an obvious water source. A quick self-test is to turn everything off and watch your water meter - if it's still moving, there's a leak somewhere. Tracking down exactly where it is usually needs a specialist detection kit, which a plumber can bring in without having to rip everything up.
What should I do if I have a burst pipe?

Turn off your stopcock straight away - you'll usually find it under the kitchen sink or where the mains water enters the property. Once it's off, open your taps to drain what's left in the system, switch off the boiler if you can do so safely, and mop up any standing water before it reaches electrics or flooring. Then call a plumber. With burst pipes, the faster you act, the less damage you'll be faced with.
What is a gas safety certificate and do I need one?

A Gas Safety Record is issued by a Gas Safe registered engineer after checking that all your gas appliances, flues, and pipework are safe. Landlords in England, Scotland, and Wales are legally required to get one every year and give tenants a copy within 28 days. For homeowners it's not a legal requirement, but getting a check done alongside your annual boiler service is a smart idea, particularly in older properties. Only a Gas Safe registered engineer can carry out the work or issue the certificate - you can check anyone's registration on the Gas Safe Register website.
Why is my water pressure low and can a plumber fix it?

Low pressure usually comes down to one of a handful of things: a stop valve that's not fully open, limescale build-up in older pipes, a failing pressure-reducing valve, or an issue with your water provider's mains supply. In most cases a plumber can sort it - though if the problem is with the mains itself, you'll need to contact your water company first. Either way, don't just live with it - ongoing low pressure can sometimes point to something more serious.
How do I know if my boiler needs replacing or just repairing?

If it's under ten years old and it's one specific fault, a repair usually makes sense. If it's over fifteen, has needed multiple fixes recently, is making strange noises, or your energy bills have crept up for no obvious reason - replacement is probably the better investment. A useful rule of thumb: if the repair would cost more than half the price of a new boiler, it's probably time to replace it.
How often should I get my plumbing inspected?

There's no legal requirement for homeowners, but every two to three years is a sensible habit - especially in older properties or hard water areas where limescale builds up over time. Your annual boiler service covers some of the associated pipework too. And if anything seems off between inspections - odd noises, discoloured water, unexplained damp - don't wait. Get it looked at sooner.
Why do my pipes make a banging or knocking noise?

That banging sound (sometimes called water hammer) usually happens when water flow is suddenly stopped or redirected, sending a pressure wave through the pipes. It's most common after flushing the toilet, shutting a tap sharply, or when a washing machine valve closes. Pipes that aren't properly secured can also knock against walls or joists. It sounds alarming but it's often an easy fix - a plumber can figure out whether it's a pressure issue, a faulty valve, or just some loose pipework.

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