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How to Drain a Plumbing System

Sometimes it can be necessary to drain the entire plumbing system in your household and this can be for a number of reasons.

For instance, you might want to fix a plumbing issue in the home, shut down the property if you’re going away for the winter months or you may well have just developed a complete phobia of water.

To help you along your way, we’ve compiled a brief step-by-step guide to aid you in doing so:

You Will Need:

• An adjustable wrench

• A long piece of wood and some string

• A common garden hosepipe

• Radiator bleeding key

draining a plumbing system

Step 1: Stopping the water system from refilling

Start by turning off the electricity or gas supply to your boiler. After this has been done, make your way into the loft and find the expansion tank for your water system. This will have a ball valve that floats and this controls the flow of water from the mains into your homes water system. Lift up the ball valve arm and tie it to a piece of wood that you can suspend on the edges of the tank. This will trick the valve into thinking the tank is full when it isn’t and stop the system from refilling.


Step 2: Draining the system

You’ll now need to find the drain nozzle on your water system. This is a small brass extension that can be fitted into a common garden hosepipe to effectively drain all of the water from your plumbing system. You should typically find it at the bottom of your water tank and sometimes there might be more than one nozzle.

Fit the hosepipe onto the nozzle and ensure that the exit of the pipe is pointing outside where the water can drain safely away. After you have done this, open the valve by turning the square brass drain cock at the end of the nozzle using your adjustable wrench.


Step 3: Bleed all of the radiators in your home

Take your radiator bleeding key (If you don’t have one, you can get one from your local DIY store of plumbers merchant) and insert it into the first radiator and turn slowly in an anticlockwise direction. Ensure that you have a cloth ready to catch any drips that come out of the radiator when doing so. If there is any trapped air within the radiator, it will emit from the valve, creating a hissing sound as it comes out. As soon as water starts to flow from the radiator, close the valve and wipe away any excess water. Repeat this process for all of the radiators in your household.

Sometimes there may be occasions where an air lock in the system will prevent the water from draining out of the radiators. If this happens, go back to your water tank and release the ball valve slightly to allow some water to flow back into the system and then tie the ball valve back up again. Once this has been done, try bleeding your radiators again.


Step 4: Reconnect the plumbing system

Once all the work has been carried out, disconnect the draining hose and close the drain cock and all the bleed valves on each radiator. Go back to your water system and untie your ball valve so that the system refills completely. When the tank has filled, re-bleed all of the downstairs radiators followed by the ones that are upstairs. Turn on your gas, electricity and your boiler and run the system to check for any leaks.


Tips for draining your plumbing system

• Some newer systems, such as a combi boiler, are commonly known as sealed systems and rely on the water pressure from the mains to function correctly. If you have one of these systems in your home, you will need a qualified plumbing engineer to carry out the work for you

• If you have very old radiators in your home, the procedure for draining them may be very different and require a professional to carry out the work for you

Please note that this guide is a rough step by step guide. Draining some plumbing systems will require a slightly different method so if you don’t feel confident with the process, make sure that you hire a plumbing professional to carry out the work for you.

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