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How To Drain a Worcester Bosch Combi Boiler?


The Worcester Bosch Combi boiler has time and again proven its effectiveness in heating homes across the UK, making it one of the most sought out boilers countrywide. But like all good things, your Worcester Bosch boiler needs regular maintenance to keep it in peak condition. One of the best practices recommended for ensuring your boiler always meets your heating needs is to drain it at least once a year. But how do you drain a Worcester Bosch Combi Boiler?

Being the experts we are at matters boilers, we advise you to call a Certified Gas Engineer to drain your Worcester Bosch Combi Boiler whenever the need arises. This is because you can tag it on the annual service, therefore, reducing your call-out fees. Alternatively, you can choose to do the job yourself in a bid to cut costs.

If you intend to go the DIY way, this guide will help you effectively drain your boiler while ensuring no harm comes to your prized Worcester Bosch Combi Boiler.

Why Should I Drain My Worcester Bosch Combi Boiler?

Draining your boiler has many benefits. Here are some that might convince you why routine draining isn’t a bad idea after all.

Reduces the risk of freezing pipes

During winter, assuming you are off on an extended holiday, or possibly you are a winter sports enthusiast, your Worcester Bosch Combi Boiler will be off for a very long time. In these freezing conditions, not draining the boiler means a risk of water freezing in the network of pipes.

Reduces the risks of water leaks

If you intend to change the rusty and repulsive radiators or change the pipework, draining the boiler is imperative to avoid massive flooding in your home, which may damage your walls and floor.

For decorating purposes

If you plan to repaint or decorate the walls in your home, you would want to paint the walls behind the radiators. Decorating your walls will be easier with the extensive pipe network out of your way.

Draining is cost-effective

Draining protects you from paying for expensive boiler repairs or boiler replacements. Sludge build-up in the system over time will cause wear and tear, and your boiler will fail eventually. The cost of repairs or replacement is considerably high and could be avoided by just draining or flushing your Worcester Bosch Combi Boiler.

When Do I Drain My Boiler?

The appearance of sludge in your system is a clear indication that you need to drain your boiler. Sludge is an undesirable accumulation of minerals and oil deposits on your boiler, resulting in staining your boiler’s walls. Sludge lowers boiler efficiency and results in higher energy usage as more of it is now needed to heat the water sufficiently. If sludge is left to accumulate for a long time, the boiler will eventually fail.

To detect sludge in your heating system, release some air from one of the radiators and watch the water coming out. If the water is coloured (brownish), it indicates sludge, and you should drain your boiler immediately. If the water is clear, your boiler will not need to be drained.

Power flushing, which a certified gas engineer should do, will also solve the sludge problem. The engineer will connect a machine to your heating system that pushes a powerful flow of fluid through it, dislodging rust and dirt from your radiators and boiler.

How Do I Drain My Worcester Bosch Combi Boiler?

The exact way of draining your Worcester Bosch Combi Boiler depends on the model of your appliance. For best results, read your owner’s manual and follow the instructions provided.

That said, here is the general procedure for draining your boiler.

Step 1:  Perform a Quick Flush

Before you even switch off your boiler, the preliminary step is to flush it to remove any sediments stuck in the boiler’s valve. By removing the residues, you open a path for faster and more efficient draining.

To flush your boiler, connect a garden horse to the boiler’s valve while the water pressure is still on. Once done, open the valve for a few seconds, then close it. The water pressure flushes out any sediments stuck in the valve. Repeat the process 2 to 3 times.

Step 2: Turn Off Your Boiler by Unplugging it from the Mains.

Once unplugged, allow the system to cool off for about 3 to 4 hours. Turning off the system enables the scolding water to cool down, and it is subsequently less likely to cause harm and injuries to yourself while draining. The long waiting duration is an extra safety measure to ensure the water leaving the radiator during the draining is sufficiently cold.

Step 3: Turn Off the Water Intake Valve

Locate the valve in the cold-water pipe above the boiler or the main water supply valve and shut off the water. This will ensure no water enters the system while you are emptying your boiler. To know whether the water intake has been cut off completely, open the water faucets in your home, which should now have low pressure.

Step 4: Open the Drain Valve

First, locate the lowest radiator in your home, then find the drainage valve situated in the lowest part of the radiator. Once you spot it, attach a long garden hose pipe to it and use a jubilee clip to hold it in place firmly. If your hose pipe is a tight fit on the drain-off valve, however, you may not need the jubilee clip. Either way, we recommend using the jubilee clip to prevent the hose pipe from slipping and causing damage to the floor through dirty water spillage.

Step 5: Drain the Boiler and Flush the Tank with Water

Release the tank vacuum by holding one end of the hot water pipe above the heater and pulling it slightly to one side. This movement will allow air to enter the tank, thus forcing the water to flow out of the open drain valve.

To make the process quick and effective, open the bleeding valve on top of each radiator in your home. Leave the water to drain out till you hear air being sucked into the system. At this point, the last remaining bits of water will be out of the system.

Once the tank is empty, flush it in increments by allowing some water to enter then draining it. Repeat the process 3 to 4 times.

Step 6: Finish the Draining Process

Now that the draining is complete disconnect the garden hose and shut off the drain valve.  When removing the hosepipe from the drain-off valve, you should be prepared with a container to avoid water spill out that may have remained.

Next, tighten the bleeding valves of all radiators in the house and reconnect the hot water pipe. Ensure you tighten the hot water pipe to ensure no leaking will occur when the system is back on.

Step 7: Refill Your Boiler

It’s only normal to let fresh, clean water into the boiler’s system after draining the sludge or oily water. You need to open the filling loop and allow the system to refill. Let the system re-pressurize to the level recommended in your manual. Then bleed the radiators starting from the lowest to remove air trapped in the system. Once the air has been released from all radiators, open the filling loop again to get the pressure back to optimal levels.

It is prudent to check the pipework and radiators for leaks before switching back on the Worcester Bosch Combi Boiler.

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