How to Drain Down A combi boiler

Photo of draining down a radiator of a central heating system

A professional is always the best person to empty a combi boiler.

If you're not sure what you're doing, it's difficult and could go horribly wrong. As a result, we propose hiring someone professional to make life easier for yourself.

However, if you have the know-how, you can accomplish it yourself. We'll also show you how to drain a combi boiler in the safest way possible.

If you're not confident doing it yourself, we strongly advise you to outsource the job of emptying a combi boiler to a professional heating engineer. Attempting it on your own may damage your heating system and jeopardize the warranty on your boiler.

When should I empty my combi boiler?

  • There are a few circumstances when you may want to empty your combi boiler:
  • You'll be swapping out the radiators or pipes.
  • To remove any obstructions from the heating system
  • If you're going away for a few days during the winter, be sure to turn off your water and drain any water from your home ahead of time.

How to drain a combi boiler

First and foremost, turn off your combi boiler and disconnect it from the power source. Before starting, wait for the water in the system to cool completely.

To drain a combi boiler, you'll need the following items:

  • Hose
  • Bucket
  • Spanner
  • Radiator valve key

1. Look for the drainage valve.

The drainage valve is typically located at the base of your heating system's lowest point. It's usually on one side of a downstairs radiator. However, it may be outside as well.

If it's outside, you won't have to worry about water spills.

2. Connect a hose to the valve

We need to direct the water that drains from your heating system outside. Attach a hosepipe to the valve, keeping the other end of the hose over a drain or somewhere you don't care if it gets wet.

Keep a watchful eye on the hosepipe as you drain the heating system since it can come off.

It's also a good idea to put a bucket underneath the valve to catch any drips of water.

3. Turn on the valve

This is when things get serious. Turn the valve to open it with a spanner. The heating system will now be emptied and sent through the hose pipe.

Wait a few minutes for the water to drain from the system.

4. Remove the cap from the upstairs radiators' bleed valves.

It's time to turn your attention to the radiators on the second floor after allowing for a few minutes for the water in the heating system to drain.

Gather your valve key and twist the bleed valve on each radiator until it opens up. The bleed valve is located at the top left or right of the radiator.

Turn the valve until you hear a vacuum sound. This indicates that the valve is open.

Water will flow down to the bottom radiator and out through the drainage valve when you open the drain cock. To get rid of any excess water, empty all of your other downstairs radiators as well.

The heating system in some houses is split into two. This means you'll have to drain water from both sides of the home's heating system.

It's easy to be caught off-guard by this. And that is just one of the many reasons why you should hire a heating engineer.

5. Tighten the valves

The heating system has been emptied once the water has stopped flowing out of the hose. Now you may tighten all of your open bleed valves around your property.

How to Fill a Combi Boiler

You'll need to fill the system with water after draining a combi boiler.

To accomplish this, locate the filling loop.

The mains water pipe is linked to the central heating pipe via the filling loop. It's typically located beneath the boiler and resembles a flexible silver hose that joins two pipes.

In the middle, you'll notice a valve at each end. To open them up and allow water to enter the heating system, turn both valves to the open position.

Keep an eye on the boiler's pressure gauge while the valves are open. The pressure should be between 1.5 and 2 on the pressure gauge, but always check the manufacturer's recommendations.

What should I do if my boiler is leaking?

One of the reasons why a heating engineer is the ideal person to empty a combi boiler is that ending up with a leak is common. And the leakage will only get worse. You should turn the water off as soon as possible and contact a professional if you detect any kind of leak, no matter how little.

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Heat Quick Direct is accredited by all the major gas boiler trade bodies, such as Gas Safe and we are approved G3 unvented hot water storage engineers approved by Worcester as accredited engineers and we are approved advanced Vaillant engineers.