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Your Heat > Boiler Installations  > Draining Down Your Worcester Bosch Boiler: A Step-by-Step Guide
Worcester Bosch boilers Sittingbourne drain down a central heating system combi boiler

Draining Down Your Worcester Bosch Boiler: A Step-by-Step Guide

Hi, thanks for tuning in.  In this blog we help you with the old age issue of how drain down a central heating system combi boiler.


Combi boilers provide households with hot water. But their functionality goes beyond this. Hot water circulates through the pipes and radiators in your household and keeps it warm. If you own a Worcester Bosch boiler or any other combi boiler, you should know it’s a good idea to drain the water out of the system from time to time, at least if you want to ensure the top performance of your boiler.

Here we explain how to drain down your boiler in a step-by-step guide and answer some related questions on this matter. It’s our duty to say it would be best to have a Gas Safe engineer do this task for you, but if you want to do it yourself, let’s get started.

Why Draining Your Boiler Is So Important

Although Worcester Bosch boilers are top of the list of best boilers out there, you still want to look after yours. Here are the 3 main reasons why you should drain your boiler:

1. You will reduce the risk of pipes freezing.

Let’s say you are passionate about skiing. That means you will be away for at least 2 weeks in the winter months, possibly even longer. In this case, your boiler is going to be turned off for 2 or more weeks as well. If you don’t want your pipes to freeze, drain that boiler on time.

2. Not draining your boiler can increase the risk of water leaks when changing pipework or having your property renovated.

If you want to remove those rusty and unsightly radiators or change pipework, not draining your boiler beforehand can result in a massive flood and damage your walls and floor.

3. It protects you from paying for expensive boiler repairs or boiler replacement.

Sludge build-up can cause your boiler to fail over time. Draining it eliminates the sludge from the system and keeps your boiler in good condition.

When to Drain Your Boiler?

Release some air from one of the radiators. Is the water coming out clear or coloured? If it has turned brownish, you should drain the boiler asap.

The Simplest Guide on Draining Your Worcester Bosch Boiler

  1. Unplug your boiler from the mains.
  2. Wait for 3 to 4 hours for the water to cool down completely.
  3. Turn off the water intake valve.
  4. Locate the lowest radiator in your home, then try to find the drainage valve, situated on the lowest point of the radiator.
  5. Make sure a hose to the draining valve is well secured so the water exits your home safely.
  6. Open the valves on top of each radiator in your home (bleed valves) and wait until there is no more water coming out.
  7. Close the bleeding valves and the drainage valve.
  8. Locate a braided filling loop underneath your boiler and open it. Let the system repressurise itself to approximately 1 bar. Put the filling loop back in its place.
  9. Check for any leaks around the boiler or radiators. If there are none – congratulations, you’ve drained down your boiler and extended its life.


We know we’ve made draining down your boiler as simple as pie, but there are several things that could go wrong if you want to do this yourself. If your boiler is still under warranty, why wouldn’t you have a professional drain it down for you? On the other hand, if its warranty has expired and there are multiple failures within the system, getting a replacement boiler would be the best idea. We supply and install Worcester Bosch boilers. Get an instant quote or contact us for more information!


We hope this helped with how to drain down a central heating system combi boiler

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