Is a Leaking Overflow Pipe Dangerous?

Tuesday 26th October 2021
by Homeforce

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Tue 26th October 2021

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Leaks and overflows are always something to be cautious about. They can, in some cases, cause further damage – some of which are unseen at first. But is a leaking overflow pipe dangerous?

We’ve been repairing leaking overflow pipes for our customers for years and know how to help. 

So in this article, we’re outlining how to approach overflow pipes – based on what the pipe is used for, and any precautions around that. Here’s the quick answer to get us started…

Overflow pipes provide a discharge mechanism for the safety valve in the system. Water pressure, if too great, can be dangerous if not dealt with. Boilers and other appliances are complex systems dealing with water, heat, and electricity. If you notice a leaking pipe, call a professional for help.

So with the short answer in mind, let’s head straight into details so you can understand a little more about leaking overflow pipes. 

Is a leaking overflow pipe dangerous?

This depends on the pipe and what it’s used for.

Overflow pipes from boiler systems, appliances, and in particular those involving heated water can be dangerous if not dealt with promptly.

External Pipes

All leaking pipes can go on to create further damage beyond the appliance.

Let’s go on to discuss this in general terms, and then we’ll move on to specific pipes.

Why you should repair the leakage in an overflow pipe

A leak in an overflow pipe is a warning sign that should rarely be ignored.

Many people think that if an overflow pipe is leaking then it’s quite normal and many of us believe that an overflow pipe is designed to discharge water.  After all, it’s an overflow pipe! Although for some pipes this is ok, for many it’s not. 

Pipes from roof guttering

For drain pipes leading down from roof guttering, it’s quite normal for you to see water discharged.

For the most part, overflow pipes are designed to let water out only if there’s an issue with the appliance. It could be down to an ill-fitting valve, pressure over the optimum line, or other types of technical flaws in the system.

Drain pipes leading from roof guttering

In most cases, overflow pipes you see on the outside of your property are linked to either: 

  • Kitchen appliances
  • Water 
  • Toilet 
  • House boiler system 

Reasons why boiler overflow pipes leak

Overflow pipes in boilers can leak for a few main reasons. 

  • too much pressure build-up in the boiler where expansion valves have failed or lost their charge
  • Where the pressure relief valves are incorrectly seated.

Pressure build-up

Pressure build-up is a common cause for almost all types of boiler leakages. 

When more than normal pressure is experienced by the boiler it releases the water from the overflow pipe to ease congestion.

If the overflow were not present, then it can result in damage or leakage from the pipe. 

This is not an issue that will go away and would need to be repaired.

Faulty valves

Another reason behind water expelling from the boiler overflow pipe is down to a loose-fitting valve designed to regulate the pressure.

When such valves are not fully closed and sealed, it can cause a leak.

This can result in excess water on the outside of the property which can cause damage way beyond just the boiler or appliance.

Overflow Pipes

Which appliances have overflow pipes?

Many household appliances are equipped with overflow pipes. 

These pipes help to expel the pressure caused by water within the system to avoid collapses and other damage.

Some modern appliances and home systems now send an alarm to the user to warn them of faulty appliances. 

What can I do if I receive an alarm or see an overflow pipe expelling water? 

The best thing to do is get in touch with a professional to repair the system before any further damage takes place. 

This is of course easy for those that have a plan to cover these eventualities, it’s just one simple phone call.

Appliances that have overflow pipes are:

  • Combination boilers
  • Sinks
  • Bathtubs
  • Washbasins
  • Dishwashers
  • Expansion tanks 
  • Washing and drying machines
  • Copper cylinders
  • Toilets 
  • Central heating systems
  • Coldwater feeds

Which boiler has overflow pipes?

Combination boilers are usually designed with overflow pipes, most modern homes have some form of boiler or combination boiler that has an overflow pipe. You should be able to clearly see this on the external wall of the property – most often situated along a wall near to the boiler position.

How to identify a boiler’s overflow pipe?

Overflow pipes for boilers are quite easy to identify only if you have a little knowledge about their built, placement, and divisions.

  • The boiler overflow pipe is usually made from tough plastics. Older systems may be made of copper or even lead. The pipe should be situated on the side of your property with access to appropriate drainage.
  • Overflow pipes for appliances and air conditioners are also situated along the side of the property. However, these types of pipes are mostly made of plastic, and the boiler pipe is often made of copper or lead.
Boiler Overflow Pipe

How to detect a leakage in the overflow pipe of the boiler

  • A continuous or regular leakage detected outside the property from the overflow pipe is often the first sign people have that there is a fault in the system. An occasional glance at your overflow pipe is advisable to detect any early signs of trouble.
  • The leakage can be detected by studying the pressure value on the boiler gauge [located on the boiler unit]. The optimum pressure in the boiler pipes should be 1.5. Although marginal fluctuations can be expected, if the pressure varies too far outside of this, then you should contact a professional for assistance.
  • Some boilers are equipped with alarm systems that warn the user of an irregular condition in the boiler by showing abnormal displays. To understand the codes on display, user guides for your particular appliance should be consulted.
  • One method for detecting leaks is the increased temperature of the boiler unit. For safety reasons, in such cases, boilers should be dealt with urgently, and handled by engineers only.
  • Flaws and leakages are also signalled by increased water and/or fuel consumption. If such problems occur, call your respective plumbing companies for regular service.
  • Corrosions, cracks, leaks, or damage to any other area or pipes leading from the boiler may indicate that a problem is occurring, this may trigger the overflow pipe too.

What to do if the overflow pipe of the boiler is leaking 

 The process involves a number of steps:

  • Identify the source – If you see a leak, make further visual checks to ensure that it is from the boiler unit – or what other appliance or source the leak is from.
  • Check the boiler pressure – If its value is above or below the expected 1.5, then this may further confirm there is an issue. In some instances, boiler pressures can be regulated, controlled or the system can be reset by the user. If this is not the case, then consult the boiler user guide for troubleshooting or consult a professional immediately.
  • If you cannot stop the leak – proceed to turn off the boiler [where possible] and call a professional for help. You should ideally consult professionals for this task. Only let a qualified engineer handle difficult cases beyond what the user manual directs.
  • Do not panic – Small drips may not be classed as an emergency, these could simply be a build of condensation. A larger leak however should be taken seriously.

The best way to fix leakages in an overflow pipe

The best and easiest method to fix a leakage in overflow pipes is to call a professional for help. For that, you can easily obtain a service subscription. Otherwise, a certified engineer is the best option to treat leakages. Paying for sporadic repairs is often a more expensive option in the long run.

If you want to fix a boiler problem yourself, then there are specific things you need to know.

It’s not recommended for people without suitable qualifications and experience to try and fix the source of a leaking pipe themselves. If you fail to take the necessary precautions you may be liable to prosecution for any damage or injuries caused.

Damage that leaks can cause

No one likes the dripping sound of a leaking pipe. But these leakages can be way more serious than just a minor annoying sound.

If you ignore leaks for long enough, they can cause greater harm to other areas of your property. 

Stained and corroded walls, green mould, or black mould growing on walls. In severe cases, this can cause problems for home foundations from water saturation or flooding.

The cost of damage can be greater than the cost of a boiler fix.

More help for your plumbing

We hope this has provided you with a good overview of whether leaking pipes are dangerous. 

In most cases, you should investigate the issue and seek to employ an engineer to repair or replace the cause. 

Of course, the simplest route is to obtain a plumbing cover plan, a boiler cover plan, and an appliance plan. One phone call can keep all your appliances covered and provide peace of mind. Why not get in touch today to request a quote.

Ready to get started? Call us anytime on 0844 77 00 597 or

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