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How To Drain Down Central Heating System

TL:DR – See Summary

  1. Switch your central heating system off (for a safety measure)
  2. Cut the water supply to your boiler
  3. Find your drain off valve on your radiator
  4. Bleed your radiators

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You may have heard people talk about bleeding, venting, or draining your radiator when you have heating problems. But what does draining your radiator actually mean and how will it help? No problem Origin GPH has you covered!

If you are a homeowner, it is important to maintain your heating system to ensure its efficiency and to avoid any issues. Therefore, it is a good idea to drain your heating system once in a while to remove sludge or repair a leak or change the radiator. Knowing how to drain your radiators and your boiler will keep your central heating system working at full capacity for your home. At Origin, we are experts at fixing, servicing, and installing heating systems.

How to drain central heating system

How to Drain Down Central Heating System

Step 1: Switch your central heating system off (for a safety measure)

Homeowners, before you start draining anything please switch off the system as a safety measure and wait until the pipes cool down completely. You want to ensure you don’t burn yourself with hot water. If you are about to do a boiler replacement or restoration let them cool also.

Step 2: Cut the water supply to your boiler

This step is important because you want to stop water from entering the radiator you are working on, this will prevent buildup as you work. Within most UK homes there should be a separate stop tap for this. However, if there isn’t one or you find it hard to turn it, simply stop the water flow by tying up the ball valve to a wood laid on top of the cistern. The ball valve is what controls the water entering the cistern

Step 3: Find your drain off valve on your radiator

A drain off valve is a useful drain point for your radiators and it is usually located on the bottom floor. To help keep mess to a minimum it’s important to drain off the water to the outside. Consider using a garden hose and clip it with the help of a clip to the outlet, so the water runs outside. If you are garden conscious you may want to direct the hose away from plants as there are chemicals in the inhibitors. If you don’t have a garden or a hose pipe a bucket will work. Just ensure you shut off the valve when you need to empty your bucket to avoid mess.

Step 4: Bleed your radiators

Now we need to drain the central heating. This can be done to clean out sludge and limescale as well as when replacing your central heating system. Open bleed valves so the water runs through the system freely without blockage. To ensure free-flowing, start with the upstairs radiator and then the radiators on the bottom floor. Again, ensure you have your bucket or hose attached at the end of the drain off valve to avoid mess. If you have air within the system that is preventing the water from flowing. Add more water to fill the tank and loosen the valve that was previously tied up. If this doesn’t work, consider giving us a call.

How To Drain Central Heating System Without Drain Valve

A drain valve is used for draining your heating system, but if you do not have one then follow these steps:

  1. Switch off your heating system and cut off the water supply
  2. Wait for the boiler to cool and discharge the water
  3. Separate the radiator by the system – close the two valves. If you have a lockshield, remove the plastic cap and use pliers to close the valve back tightly
  4. Bleed your radiators
  5. Loosen the coupling nut and place a bucket under it with old towels
  6. Rotate the nut anticlockwise until you see the water start to spill into the bucket
  7. Attach a hose then drain the system


How Long Will It Take To Drain a Central Heating System?

Usually, it should take between 10 to 15 minutes, however, this depends on the size of your house and how many radiators you have. The more radiators you have, the longer it will take to drain down central heating. To speed up the process, systematically open the bleed valves on every radiator in your home. If you have a drain-off valve it can take 20 minutes to an hour to complete.

How Often Do I Need To Drain My Central Heating System?

Boilers can break down regularly, roughly 20% of boilers can break down in a given year. However, one of the silent killers of boilers are sludge and limescale build up. If you want to save money on costly repairs and extend the lifetime of your boiler. We recommend draining your boiler system once a year; keeping your boiler happy and your pockets full!

Do You Need To Turn The Water Off If You Have a Combi Boiler?

No. You don’t need to just turn the heating off so there’s no power to the boiler. If you want to drain your combi boiler, after turning off the boiler and disconnecting it from the power supply, wait until the water has cooled down. Then connect the hose to the drain valve, all the bleed valves need to be opened to let all the air escape, start from the highest level in your home, and open radiator valves. You should hear air coming out of the radiator. Open the drainage valve using a wrench or spanner, and expect some water to come out. Once the water is gone, close the valve. When they are all emptied, you have successfully drained your central heating system.

Contact Us If You Need Help With Your Boiler

The above will help keep your heating system operating efficiently and will save you money from repairs in the long haul. If you found the following information above useful, why not check our other blog on Most Common Boiler Issues and How to Prevent Them. At Origin, we look after our customers. Contact us if you are having trouble with this or any other queries you may have. We cover areas across Glasgow. Our heating engineers are highly trained and experienced to give you the best experience possible. Take a look at our outstanding reviews and see what our customers say!

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