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Boiler condensate pipe regulations explained

A HomeServe engineer pouring boiling water from a kettle over a boiler condensate pipe outside.

If you’re a homeowner or landlord, you might be thinking ‘Why on earth do I need to know about boiler condensate pipe regulations?’ The reason is because incorrectly installed boiler condensate pipes have been the source of a disproportionate volume of boiler breakdowns over the last 10 years.

If you have a condensing boiler, then it’s a good idea to know if your condensate pipe has been installed in line with current regulations, so it doesn’t freeze in winter and stop your boiler in its tracks. This guide will tell you all you need to know to avoid a breakdown.


Table of contents

  1. Why are boiler condensate pipe regulations are in force?
  2. Why do condensing boilers break down in cold weather?
  3. How a does a condensing boiler work?
  4. What causes a condensate pipe to freeze?
  5. Where does your condensate pipe discharge?
  6. Do you need a new boiler?
  7. FAQs

Why are boiler condensate pipe regulations are in force?

In April 2005, building regulations were revised to state that all new oil or gas boilers needed to be condensing boilers, in an effort to reduce the UK’s carbon footprint. It meant that only highly efficient condensing boilers could be installed from that moment on, and this has been a significant breakthrough in reducing the country’s carbon footprint.

Why do condensing boilers break down in cold weather?

Since 2005, weather trends like extended periods of frost have caused an increase in condensing gas boiler breakdowns. These breakdowns happen when the condensate discharge pipe freezes, resulting in homeowners having to thaw their condensate pipe.

How a does a condensing boiler work?

A condensing boiler is any boiler that uses condensing technology to reuse the heat they generate from burning fuels such as gas or oil.

​​Before 2005, older, non-condensing boilers wasted between 30-50% of heat due to combustion gases escaping via the flue. A condensing boiler, in comparison, can be up to 92% efficient.

This is because in a condensing boiler, the latent heat flue gases can be repurposed and reused to preheat the cold water coming into the boiler. During this process, the temperature of the flue gas is rapidly reduced from around 130℃ to 90℃.

As the gases cool, condensation is produced. A condensing boiler will produce about 2 litres of condensate an hour at an average temperature of 30-40℃. This condensate needs to drain into your waste water outlet or to a drain via your condensate pipe.

But I’ve got a combi boiler!

A combi boiler can also be a condensing boiler. If your boiler was installed after 2005, then it’s 99% probable that it’s a condensing boiler because of the regulations.

What causes a condensate pipe to freeze?

So, back to the issue at hand. In the majority of boiler breakdowns caused by the condensate pipe freezing, the condensate discharge pipe has been fitted externally to the property. This can be for just some of its length or all of it.

This external fitting exposes the pipe to extreme winter temperatures and directly influences whether it freezes and causes the boiler breakdown or not.

For this reason, the UK’s Heating and Hot Water Industry Council (HHIC) has published guidance on condensate pipes for installers, pointing to the current British Standard BS6798, which states that ‘wherever possible, the condensate drainage pipe shall be terminated at an internal foul water discharge point’.

They add that: ‘Where there is no other option than to run the pipe externally, the pipe needs to be increased to at least a 30 mm inside diameter and insulated to help prevent freezing.”

If you need to thaw a condensate pipe, follow our step-by-step guide to help you get your boiler up and running quickly and easily. If this doesn’t help and you’re still having problems, get in touch with us and we’ll be happy to help.

Where does your condensate pipe discharge?

It’s a really good idea to know where your boiler’s condensate pipe discharges to. If it’s an external pipe, then if it’s not the recommended internal diameter and adequately insulated, you could be running the risk of your condensing boiler freezing up and conking out this winter.

If you’re about to buy a new condensing boiler or you’re renovating a kitchen or a whole property. It’s important to be aware of this. So let’s look at the HHIC’s guidance in more detail.

HHIC condensate pipe guidance when installing a new boiler

The HHIC states that: ‘Where an installer is fitting a new or replacement boiler, the condensate discharge pipe should be connected to an internal ‘gravity discharge point’, such as an internal soil stack (preferred method), internal kitchen or bathroom waste pipe such as sink, basin, bath or shower waste.

External pipes from sink wastes or washing machine outlets should be:

  • A minimum of 30mm internal diameter
  • Insulated with waterproof UV resistant material
  • Terminated below the grid but above the water line with a suitable drain/leaf guard fitted
  • The end of the waste pipe should be cut at 45 degrees where it terminates into the grid to help reduce the potential for the pipe to freeze

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FAQs

Where should a boiler condensate pipe go?

The HHIC states that:

“When fitting a new or replacement boiler, the condensate discharge pipe should be connected to an internal ‘gravity discharge point’, such as an internal soil stack, internal kitchen or bathroom waste pipe such as sink, basin, bath or shower waste. Where there’s no other option than to run the pipe externally, the pipe needs to be increased to at least a 30 mm inside diameter and insulated to help prevent freezing.”

How much water does a condensate boiler produce?

A condensing boiler will produce about 2 litres of condensate an hour at an average temperature of 30-40℃. This condensate needs to drain into your waste water outlet or to a drain via your condensate pipe.

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About the author

Brian became a fully qualified gas engineer in 2009 and has been with HomeServe since 2012 after a couple of years being self employed.

Brian was a Gas Engineer for six years at HomeServe before progressing to a Service Excellence Coach (SEC) role in 2018. The main purpose of the SEC role was the coaching and training of existing engineers as well as attending problem or complaint jobs.

Brian became a Self Fix Engineer in 2021, where he developed the Self Fix Tool guide that the call centre agents use to help our customers carry out simple user adjustments to get their boiler back up and running.

Qualifications

ACS, NVQ Level 3 Plumbing & Heating, IOSH, Unvented, Level 3 Team Leadership / Business Admin

Years qualified

Since 2009
Read more

Share this post

About the author

Brian became a fully qualified gas engineer in 2009 and has been with HomeServe since 2012 after a couple of years being self employed.

Brian was a Gas Engineer for six years at HomeServe before progressing to a Service Excellence Coach (SEC) role in 2018. The main purpose of the SEC role was the coaching and training of existing engineers as well as attending problem or complaint jobs.

Brian became a Self Fix Engineer in 2021, where he developed the Self Fix Tool guide that the call centre agents use to help our customers carry out simple user adjustments to get their boiler back up and running.

Qualifications

ACS, NVQ Level 3 Plumbing & Heating, IOSH, Unvented, Level 3 Team Leadership / Business Admin

Years qualified

Since 2009
Read more

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