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Boiler Condensate Pipe Regulations


Over the years, the weather patterns in the United Kingdom have become more extreme because of climate change. We now have to deal with cold and prolonged sub-zero temperatures.

As a result, the Heating and Hotwater Industry Council (HHIC) has provided new guidelines to help us deal with these extreme weather patterns. Specifically, much attention was directed towards boiler condensate pipes.

In the new January 2021 regulations, they have advised homeowners to steer away from external condensate pipes that are prone to freezing. Instead, they insisted that all condensate pipes should terminate internally.

We’ve decided to split the boiler condensate pipe regulations into two:

  • For installers
  • For homeowners

Boiler condensate pipe regulations for installers

It’s the installers duty to inspect the homeowner’s condensate pipe installation when servicing or repairing a boiler. If the installation is external, he or she has to see and confirm if the pipe can be terminated internally, as per the new regulations.

On top of that, it’s the technician’s responsibility to educate and advise the homeowner on the required work. He or she must also provide the homeowner with an information leaflet that must be filled for future reference.

Below is a summary of the boiler condensate pipe regulations for installers.

  • Ideally, when replacing or installing new condensate pipes, they should terminate at internal “gravity discharge points.” Internal soil stacks are the most recommended.
  • Additionally, kitchen and bathroom waste pipes carrying sink, bath, and shower waste should also terminate internally.
  • Installers should also be mindful of the pipes’ dimensions and material. According to the regulations, external waste pipes from sinks and washing machines must have a minimum internal diameter of 30mm. On top of that, they must have a minimum of 13mm pipe insulation that is UV resistant and waterproof.
  • To prevent damage caused by wind chills and debris, the installer should also install a suitable drain guard.
  • The end of the external waste pipe has to be cut at 45 degrees to give it a sharp profile that helps reduce the chances of freezing. Also, the insulation should continue to the end of the pipe.
  • To further prevent freezing, you should seal the pipe insulation to the wall.
  • When deciding the length of the condensate pipe, a slighter longer pipe to the termination point is preferred to a shorter one running directly to an external drain point.

Indeed, the connections will vary from one boiler to another. Despite the stipulated regulations, the HHIC still advises installers to follow the correct connections, as per the boilers’ manufacturers.

Where it’s not possible to apply gravity discharge, the HHIC advises them to use condensate pumps. For example, if there is an appliance or anything in the way preventing access to the internal termination point.

Condensate pumps

Condensate pumps are good alternatives in situations where it’s not possible to directly connect the boiler condensate pipes to an internal “gravity discharge point.” The condensate pipe is connected to the pump which in turn, connects to the internal soil stack. Of course, the pump specifications should match the boiler’s and pipe’s requirements.

External conditions

As an installer, the HHIC allows you to consider an external boiler condensate drain only if an internal one is impractical to install. Nonetheless, you’ll have to adhere to some requirements.

For example, the pipework from the boiler should have a minimum internal diameter of 19mm. Nonetheless, you should stick to the manufacturer’s specifications, if there are any. On top of that, the pipe’s material should be standard. Although there are other materials, Polyvinyl Chloride (PVC) is the most recommended.

Even though the termination point is external, you should make sure the pipes run internally for as long as possible before going outside. Additionally, the external pipes should have internal diameters of 30mm and external diameters of 32mm.

As the pipe cuts through the wall to the outside, you should ensure it has a slope of at least 3 degrees. The slope is vital for maintaining good condensate velocity as it exits the building.

An external soil stack is the recommended external termination point for condensate pipes. However, the HHIC only allows it if the downpipe makes its way to a combined foul and rain-water discharge system.

Finally, the installer must introduce external air breaks between the condensate discharge pipe and downpipe. The air break is essential to prevent the back-flow of sewage into the boiler. Back-flows are likely to happen if the downpipe gets frozen, blocked, or flooded. Nevertheless, air brakes won’t be necessary if the boiler’s condensate trap has a minimum condensate seal of at least 75mm. When it comes to soakaways, you are advised to follow the manufacturer’s requirements.

Unheated areas in building

In January 2021, the HHIC came up with new regulations that specifically targeted condensate pipes in unheated areas like basements and garages. Pipes in such locations must be insulated accordingly against cold spells. On top of that, the joints (especially elbow joints) must be tightly connected to prevent breakage.

Boiler condensate pipe regulations for homeowners

As the homeowner, you are expected to listen to the engineer’s advice regarding condensate pipes.

If you have external condensate pipes, you should allow the engineer to diagnose the situation. In addition to that, expect the engineer to label the pipes for future work. He or she might also give you a filled leaflet that is important for future instalments and repairs.

If your boiler is at medium-risk, you can set a higher boiler thermostat setting that will get the boiler to operate at a higher flow temperature. The higher flow temperature will subsequently reduce the amount of condensate production. In turn, this will reduce the chances of pipes freezing during cold spells. However, it will reduce your boiler’s efficiency.

What to do with frozen condensate pipes

  1. Find the blockage

External condensate pipes have a habit of freezing at joints, elbows, and exposed surfaces.

  1. Defrost the frozen section

The easiest solution is to pour hot water or place hot microwaveable heat packs on the frozen section.

  1. Reset the boiler

After thawing the section, restart your boiler. For most units, you can do this by pressing the “reset” button.

If all this fails, and your boiler still won’t start, we advise you to call in the professionals. Even if it works, you are advised to seek a certified engineer to assess the situation and prevent future problems.

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