How to Drain a Combi Boiler
There are a number of reasons why you may want to drain your combi boiler; however, it is important that the work is carried out correctly. Draining your boiler could save you money, but not draining it correctly could do quite the opposite, so it’s much safer to leave it to the experts!
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Why should you drain your combi boiler?
Generally speaking, the main reason why you should drain your combi boiler is to eliminate any build up of sludge and limescale from your radiators and pipework.
You may also choose to drain your combi boiler to avoid coming home to frozen pipes if you are going to be away from home during the winter months.
We highly recommend leaving the job of draining your combi boiler to a professional team. Attempting it yourself could result in damage to your heating system and may void your warranty.
When should I drain my combi boiler?
There are a few occasions in which you may want to drain your combi boiler:
- You are going to replace the radiators or pipes
- To clear any blockages from the heating system
- To avoid coming home to frozen pipes in the winter if you plan on going away for a while
Do I need to drain my combi boiler to change a radiator?
Yes, before you fit any new radiators or pipes, make sure you turn off the water and drain the system.
This will help to remove any debris within your heating system, making it ready for your new radiators.
How to drain a combi boiler
We always suggest seeking professional help to drain your combi boiler, however, listed below is a step by step guide on how to drain your boiler if you feel confident to do so.
The first thing you should do when draining your combi boiler is switch it off and disconnect it from the power supply. You should wait until the water in the system has cooled right down before starting.
Some equipment you will need include:
- A hose
- A bucket
- A spanner
- A radiator key
1. Find the drainage valve
You will find the drainage valve at the lowest part of your heating system, normally to one side of a downstairs radiator.
However, it could be outside. If it is outside, then you won’t have to worry so much about spillages.
2. Attach a hose to the valve
You will need to lead the water that will drain from your heating system outside. To do this, fit a hosepipe to the valve and leave the other end over a drain or somewhere you don’t mind getting wet.
Be sure to keep a close eye on the hosepipe as you drain the system, as it may come off. It’s a good idea to put a bucket underneath the valve to catch any dripping water.
3. Open the valve
Using a spanner, turn the valve to open it. Water will now drain out of the heating system and through the hosepipe.
Wait a few minutes for the water to drain out of the system.
4. Open the bleed valves on the upstairs radiators
Once you’ve given the water a few minutes to drain from the heating system, you will need to move your attention upstairs.
Using the radiator key, turn the bleed valve on each radiator to open it up. You can find the bleed valve at the top right or left of the radiator.
Turn the valve until you hear a hissing noise. This means that the valve is open and it will allow the water to the lowest radiator and eventually out through the drainage valve.
You should also drain other downstairs radiators to remove any excess water.
5. Tighten up the valves
Once the water has stopped running, your heating system will be drained. You can now tighten up the drainage valve and all the open bleed valves.
How to refill a combi boiler
Once you’ve drained your combi boiler, you will need to refill the system. To do this, you will need a filling loop.
The filling loop connects the mains water pipe with the central heating pipe. It is normally found under the boiler and looks like a flexible silver hose connecting two pipes.
There will be a valve at each end which will both need to be turned to open to allow the water to flow into the heating system.
When the valves are open, you should be keeping an eye on your boiler’s pressure gauge. It should sit somewhere between 1.5 and 2, but you should always check the manufacturer’s instructions.
Once the pressure gauge is correct, you can close both of the valves. Your combi boiler will now be refilled.
Please note that different boilers have different types of filling valves. You need to check the manufacturer’s instructions for your particular boiler.
How often does a combi boiler need topping up?
The pressure in your combi boiler will usually need to be topped up once or twice a year.
The benefits of combi boiler draining
The advantages of draining your combi boiler include:
- Removal of sludge and sediment build-up
- Improve the efficiency and functionality of your boiler
- Prolong its lifespan
- Prevent other issues from arising
- Keep you clear of unnecessary or preventable repair bills
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