Why is My Boiler Leaking Water From the Overflow Pipe?

If your boiler is leaking water from the overflow pipe, there could be several causes. To rule out any potential issues, contact a Gas Safe engineer for an extensive examination of both the pipe and its surrounding areas.

Leaks are often caused by corrosion in pipes and other components of your heating system. Fortunately, this problem can typically be corrected by replacing washers or fittings.

Pressure Release Valve

Have you noticed water dripping around your boiler? This could be an indication of an ailing overflow pipe. While this is an essential safety feature of any heating system, its invulnerability does not make it immune – and when it leaks, this is a clear sign that something is wrong with your setup.

If the overflow pipe is leaking, it’s essential to identify what’s causing the issue and get it resolved promptly. The best way to do this is by contacting a qualified engineer who can inspect and fix the problem for you.

No matter the type of boiler you own, there may be various reasons why it may be leaking. Common causes include pressure issues, loose fittings or cracks in the overflow pipe; in extreme cases, replacement of this component might be necessary.

One of the primary causes of an overflow pipe leaking is a broken pressure relief valve. This device functions to release extra water when under too much pressure and should be replaced immediately to avoid any further damage.

Pressure relief valves should be constructed from materials compatible with the liquid they release and suitable for operation at their expected operating temperature. This is especially crucial when dealing with fluids like oil or gas that may contain various chemical properties.

Another factor to consider is the type of seal used in a pressure relief valve. Buna-N is widely used, but other manufacturers offer alternative solutions as well.

Other possible seal materials might include fluorocarbon, EPDM or silicone. Although more costly, these should be able to withstand the pressure of an overflow pipe’s fluid.

If your overflow pipe is leaking, it’s worth checking the boiler pressure to determine if the issue arises due to low or high pressure. If there’s too much pressure, this could indicate damage to an expansion vessel or PRV.

If your overflow pipe is leaking, the best course of action is to contact a certified engineer who can come and repair it for you. They should be Gas Safe registered and capable of certifying their work so that you can rest assured knowing your home’s plumbing system is in excellent hands.

Pressure Relief Valve

Have you noticed water seeping from the overflow pipe of your boiler? If so, it could be indicative of either too much pressure in the system or that an expansion vessel has failed.

Dealing with this situation can be dangerous, so it’s always best to call a professional for help. Before reaching out for assistance, there are some things you can try yourself first.

One of the primary causes of leaks from overflow pipes is that a pressure relief valve isn’t seated correctly. This could be due to sediment inside or an unfamiliar new valve that’s not installed correctly.

Pressure relief valves must be set to a certain pressure, known as blowdown, before they can reseat themselves. Doing this helps prevent chatter and seat leakage that could cause your system to run hot or cold or damage the relief valve itself.

Depending on the design of a relief valve, this may be done via an external or internal knob/handle that bolts onto the outside. It’s also possible to adjust the spring with partial valve disassembly; however, these procedures should only be undertaken by certified engineers.

Pressure relief valves must be capable of handling both the fluid they are working with and its operating temperature. This could involve a range of materials, from brass and plastic to copper and stainless steel.

Many companies utilize a variety of materials for their relief valves, as these must be able to withstand the various liquids present in a facility. Popular options include Buna-N, EPDM, silicone and fluorocarbon.

People often experience issues with their pressure relief valves, so it’s essential to be aware of what you’re up against before taking action. This is especially true if you’re a homeowner as having an expert fix the problem can be costly. Fortunately, repair these types of issues yourself if you possess the correct knowledge and tools.

Float Valve

If you notice a persistent leak from the overflow pipe outside your home, it could indicate an issue with the boiler. Take action quickly and correctly as a prolonged leak could cause extensive property damage as well as unwanted mould growth.

First and foremost, inspect the pipe for damage. If you spot a crack, this could indicate that either your pressure release valve is not installed correctly or there has been an accumulation of pressure due to an issue with your expansion vessel.

Your overflow pipe may have come loose due to an increase in pressure, so if this is the case you need to call a gas safe engineer immediately for repair work.

A float valve is the ideal solution for water level control applications since they require no electrical power to function. They feature a float ball which lowers with liquid level, opening or closing the valve accordingly. You can find them in various applications from small toilet tanks to large industrial ones, helping keep their contents at pre-set levels.

When selecting a float valve, there are various types to choose from. Make sure the one best suited to your application performs optimally and functions effectively.

Like all plumbing parts, the float valve should be securely attached to the wall of the tank it is being used in. This step is especially crucial since float arms can cause considerable torque on tanks with thin walls or glass fibre walls; therefore, resistance from these walls must be provided by them.

Another consideration is whether or not the float valve can handle the weight. In order for it to withstand pressure from water in the tank, reinforcement of its arm may be necessary.


Your boiler’s overflow pipe is designed to discharge water from a storage tank or cistern when the pressure relief valve fails or the float valve fails. Overflow pipes are essential for safety and convenience in your home’s water storage system, but they may also lead to problems if they leak.

If your boiler is leaking from the overflow pipe, there could be many reasons for it. To begin with, identify where the leak is coming from and then decide how best to address it. If it’s a minor leak you may be able to handle it yourself with some basic plumbing knowledge; otherwise, hiring professionals is recommended for effective repair work.

Another common cause of overflow pipe leaks is if the washer is malfunctioning. This component, located between the float valve and overflow pipe, works to stop water from entering when the float valve is closed.

A malfunctioning washer can lead to the overflow pipe leaking, so you should replace it as soon as possible. Replacing this component is simple and only costs a couple of pounds from your local home improvement store.

Washers are machine components used in conjunction with threaded fasteners to distribute load and prevent screws from loosening. They come in a range of materials, including metal and plastic.

They are typically protected with a corrosion-resistant substance such as zinc, cadmium, or nickel.

However, they can also be made from non-corrosive material like copper or brass. This is an ideal option for older fittings that cannot withstand modern water’s high mineral content.

A common cause of a leaking overflow pipe is limescale buildup, which can easily get trapped between your washer and overflow pipe and cause it to leak. If your washer has been exposed to limescale for an extended period of time, it could need replacement altogether.

Recommended Articles