How to drain a Worcester Bosch combi boiler

combi boiler

When it comes to boilers, there are many questions that people ask, due to the fact that so many people have a boiler. One of them is: how do you drain a Worcester Bosch Combi boiler.

Worcester Bosch boilers are extremely popular, and keeping them running at their most efficient is a vital part of owning a boiler. This is why the question of how to drain them is so important. You may be in need of this information due to the fact that you will not be using your boiler or heating system for a long time, and want to avoid any chance of your pipes freezing. You may simply want to flush out your heating and radiators, which would mean draining your boiler. You also may be having work or repairs done and do not want to risk flooding your property.


Attempting to drain a boiler cannot be simply carried out unless you have sufficient knowledge and skills. If anything was to go wrong you would be at risk of damaging or even breaking your heating system altogether, as well as doing damage to your home. You should seek the help of a Gas Safe engineer if you do not have the correct knowledge or skills on how to drain a radiator. If you decide to replace your boiler instead, you can compare Worcester Bosch boiler prices here, or research a new boiler cost here. You may also be entitled to a free boiler grant, if you meet certain criteria, it’s certainly worth checking.

How to drain the boiler

Of course, this question is subjective to what boiler you have installed. All boilers will have different specifications and require different steps to draining the system. This, of course, means that before doing anything you should read the boiler manual and ensure that you are familiar with all the parts of your boiler and what you are doing.

We will take you through a step-by-step on how to drain your Worcester Bosch Combi boiler.

  1. Ensure that the boiler is switched off and is no longer connected to the power supply. This is the first and one of the most important steps. The boiler must not be turned on.
  2. Give the water time to cool down, it is important to ensure that the water is cool before anything is drained so that the people that are working on it are not at risk of being harmed.
  3. After you have given the water time to cool down, you must connect a hose tightly and securely to the drainage valve. This is generally at the lowest point of the lowest radiator in the house or property in question. If you are unsure of this then you should consult a gas safe engineer or a professional.
  4. Once the hose is safely attached, the valve on the radiator that the hose is attached to is opened and the water will begin to drain from the system.
  5. This process of drainage can be quicker by way of opening the vents at the top of each radiator, however, you need to remember that you must know what you are doing and have the skills to carry out these steps, to avoid any damage or destruction of your heating and boiler.
  6. Once the water has all gone and you have successfully drained it, you can close the bleed valve, and the process is complete.


So these are the basic steps of draining a Worcester Bosch Combi Boiler, however, as we alluded to at the start, all boiler systems and different boiler types will have different specifications. So, ensure that you are sufficiently skilled, following the correct manual for your specific boiler and performing all the steps in a safe, controlled manner.