A leaking boiler is one of the most common issues we see in homes across London. Many homeowners first notice a small drip under the boiler or a wet patch on the floor. Others hear strange sounds or notice a drop in pressure. No matter how small the leak looks, it is a sign that something inside the boiler is not working as it should.
At Vaillant Boiler Service Experts London, we help hundreds of customers every year with leaks of all types. In this guide, we explain why your Vaillant boiler may be leaking water, what each cause means, and when you should call an engineer. We use simple language so you can understand what is going on and make the right choice for your home.
A leak does not always mean danger, but it should never be ignored. Water inside a boiler is under pressure and passes through many parts. When one part fails, even a little water can escape. Small leaks often grow into bigger ones. Big leaks can cause damage to floors, walls, wiring, or the boiler itself.
If water is dripping from your boiler, turn it off and call a trained Gas Safe engineer. Do not try to take the boiler apart yourself.
One of the most common causes of leaks is a pressure relief valve, also known as the PRV. This valve’s job is simple: it protects the boiler if the pressure inside gets too high. If the system builds too much pressure, the PRV releases a small amount of water to keep things safe.
If you see water coming from a pipe that leads outside, the PRV may be opening too often. This is not normal and needs an expert to check why the pressure keeps rising.
Your Vaillant boiler has a part called an expansion vessel. When water heats up, it expands. The vessel gives the extra water space to move. If the expansion vessel loses air or fails, it cannot do its job. When this happens, the pressure rises too fast and the boiler forces water out through the PRV.
An engineer can pump the vessel back to the right level or replace it if needed.
Boilers have many joints and pipe connections. Over time, heat and pressure can make these joints loosen. Even a tiny gap can cause water to leak.
If the leak is coming from a joint, an engineer may be able to tighten it or replace the washer or seal.
Your boiler has rubber seals inside it. These seals keep water moving through the right channels. As years go by, rubber can dry out, crack, or become hard. When this happens, leaks appear.
Replacing seals is a job for a trained engineer. If the boiler is old, the engineer may suggest a wider repair or replacement.
The heat exchanger is one of the most important parts of any boiler. It warms the water that flows around your home. If the heat exchanger cracks or corrodes, water can leak into the boiler chamber.
This is a serious issue. Heat exchangers are costly to replace and must be handled by a Gas Safe engineer.
If the heat exchanger has failed, the boiler may not be worth repairing, depending on age and model.
London water is hard and full of minerals. Over time, this can cause corrosion inside your boiler or heating system. When metal parts weaken, small holes form and water escapes.
Corrosion usually means either parts need replacing or the system needs treatment, such as a chemical flush.
Modern Vaillant boilers are condensing boilers. They produce condensation while running, which is carried away through a condensate pipe. If this pipe becomes blocked, cracked, or frozen, water can escape.
This is often a simple fix, but it must be done safely.
A boiler that has not been installed or serviced correctly is far more likely to leak. In some cases, we see boilers where the wrong fittings were used or pipes were not sealed well. Over time, these mistakes lead to leaks.
This is why it is vital to use a trained, qualified Vaillant engineer.
If your boiler is leaking, follow these steps:
Waiting too long can turn a simple fix into a major repair.
At Vaillant Boiler Service Experts London, we specialize in repairing and servicing all Vaillant models. Our engineers are trained to find the cause of leaks fast and fix them safely.
Our services include:
We work across London and offer same-day or next-day visits.
A leaking Vaillant boiler is not something to ignore. Even a slow drip can grow into a bigger problem. The good news is that most leaks can be fixed quickly when caught early. If you notice water around your boiler, it is best to call a trained engineer right away.
For fast and expert help, contact Vaillant Boiler Service Experts London. We are ready to get your home warm, safe, and leak-free again.
