What Is a Boiler Condensate Pipe?

A vital piece of equipment in your boiler, but you’ve probably never heard of it, a condensate pipe which helps to remove acidic waste water to outside drains. It’s easy for pipes to freeze when temperatures drop which means they are likely to be blocked and stop your boiler from working. Luckily, most leading combi boilers will show an error code to say that there is a frozen condensed pipe if the boiler has shut down, in which case it’s time to seek assistance.

There are a number of ways to look after condensate pipes, to ensure that your boiler is working at its best.



What are condensing boilers?


Since regulations came into force in 2005, every boiler sold in the UK needs to be a condensing one. They can vary between vent, sealed system boiler or combi from a range of leading manufacturers such as Worcester Bosch, Vaillant, Baxi or Viessmann.

Their impressive energy efficiency compared to non-condensing is what makes them a huge improvement for the home. They extract excess heat from waste gases that would usually be wasted but instead are repurposed for good use. There are two heat exchangers which help to recycle the excess heat and bring it back into the system when operational.




What is a boiler condensate pipe and what does it do?


As boilers have become more modern and energy efficient, gas boilers in particular are able to recycle heat from waste exhaust gases which turn into condensation. In contrast to old-fashioned non-condensing boilers that just extract heat from burning gases, they are more efficient. However, just to the vaporising process, this build-up of excess water can cause issues.

Condensate pipes are able to help extract this and can be found at the back of the boiler, down an external wall and into a drain. In a typical hour, they can produce 2-3 litres of condensate water when the boiler is on and is released when the volume has hit its limit in 300ml increments. Instead of being released all in one go is so that the risk of the water freezing in the external pipe which can lead to blockages is reduced.




Why are condensate pipes important?


From a safety point of view, condensate pipes are very important. They drain any dangerous fumes that have built up over time and let them escape the home safely. Also, as the pipes help with the recycling process of excess heat it helps to continue heating your home.



What size do I need?


All newly installed boilers will come with a condensate pipe, but if you’re replacing your current one then it’s beneficial to know the correct size and type – especially as condensate is slightly acidic and needs to be released in small amounts.


There are three areas to bear in mind:

• A minimum of 21.5mm for the internal overflow pipe is needed

• A minimum of 32mm for the external installation of the overflow pipe is required

• As the contents contain a small about of acid the pipe needs to be made from plastic such as PVC so that it is durable


When installing the pipe it needs to be positioned correctly to aid the release of the contents to the drain, therefore a minimum decline suggested would be 44mm per metre. If there isn’t a drain present then a product called a ‘soakaway’ is a convenient solution. Instead of draining liquid, it absorbs the condensate through limescale chipping which soaks and neutralises the wastewater.



Issues with condensate pipes


As with any plumbing part, a condensation pipe on a boiler is no stranger to facing potential issues. Winter is a particularly challenging time with subzero temperatures which may cause the external pipe to stretch and freeze. This can also happen in areas where there is little heat such as in an outhouse, garage or down an external wall of your property.



How to prevent a frozen condensate pipe


In order to keep your boiler waste pipe from freezing there are a number of steps to take.

•If there is any section of the pipe which is exposed to the outdoor air which can be prone to freezing in the winter, then make sure it has been insulated correctly. This can be done with household items that are specialised materials and can be bought from a DIY shop.

• Ensure that the pipe is less than 3 meters from the boiler to the drain.

• When installing the condensate pipe, check that it is at a reasonable downward gradient to refrain from any backsplash travelling back through to the boiler.



How to unfreeze a condensate pipe


It’s pretty simple to identify that your condensate pipe has frozen by looking at the boiler interface and seeing any error messages. It will also ‘lockout’ so that you’re unable to use it until a blockage has been unfrozen. But how do you unfreeze it? Although it’s a common issue with boilers in the UK, it’s also one that is easily fixed with warm water.

When you’ve found the frozen section of the pipe outdoors, apply hot water between 60-70 degrees to help thaw it out. If it seems to be taking longer than you first thought, then repeat the same process until complete with watering cans or in some instances by using a hot water bottle. In some circumstances, you may need to cut out the section that has been frozen, but this is unlikely.



See what CS Boxall can do for your boiler


CS Boxall are professionals in delivering all your plumbing needs including boiler repairs and installation and central heating installation and repair. We understand the need for an efficient and effective service and offer a 24-hour emergency call-out when you need expert assistance the most.

Our years of experience and knowledge mean that we can identify a wide range of challenges and address them at a time that suits you best whilst causing as little disruption as possible. Clients new and existing come to us time after time because we supply, install and provide maintenance on a leading line of boilers complete with a service that is a high standard.