Draining your plumbing system might sound like a task only needed during major repairs, but it’s something every homeowner should know how to do safely.
To help you carry out the process correctly, in this article, we’re going to explain when and how to drain your plumbing system without causing accidents or damaging your pipework. But before we do that, we’d first like to touch on why you might need to drain your plumbing system in the first place.
Why You Might Need to Drain Your Plumbing System
Most commonly, homeowners need to drain their plumbing systems when repairing or replacing pipes, fixing leaks in the system, and carrying out bathroom or kitchen upgrades. Other reasons that might require you to drain your plumbing system include:
- Preventing frozen pipes during winter
- Replacing taps, valves, or fixtures
- Performing maintenance on outdoor plumbing
- Preparing for long-term travel
Step 1: Turn Off Your Water Supply
Before draining your plumbing system, you must shut off the water to your home first. This will prevent water from flowing back into the pipes while you’re trying to empty them. Most homes have a mains stopcock located:
- Under the kitchen sink
- In a cupboard near the front door
- In a utility room
- Under the stairs
When you find it, turn the stopcock clockwise until it is fully closed.
If you’re working on an outdoor pipe or a specific area of your home, you may also have isolation valves that allow you to shut off water to a smaller section instead of the whole property.
For more guidance on how to shut off your water supply, read our dedicated article, which covers every step of the process in more detail.
Step 2: Open All Taps to Release Pressure
Once the water is off, you need to release the pressure in your pipework. Start by turning on all the taps in your home, beginning with the highest faucets (such as bathroom sinks upstairs) and working your way down to the taps at the lowest point.
Once all taps are opened, let the water run until it stops or slows to a drip. This helps the water flow out evenly and prevents air from getting trapped inside the system.
Step 3: Flush All Toilets
Don’t forget about the water stored inside your toilet cisterns. Flush every toilet in the house to empty the tanks. This helps drain a significant amount of water quickly and ensures there’s no remaining pressure in the system.
After flushing, keep the lid open so you can check whether the cisterns refill (they shouldn’t if the water supply has been turned off correctly).
Step 4: Drain the Hot Water System
Your hot water system also holds a substantial amount of water that must be emptied safely. The process you need to follow will depend on your hot water system.
If you have a combi boiler, just run the hot taps until the water stops flowing. This flushes the remaining hot water out of the pipes. If you have a hot water cylinder, the process is a bit more complicated, so follow the steps below:
- Switch off the boiler or immersion heater
- Allow the water inside the tank to cool
- Locate the drain valve at the bottom of the cylinder
- Attach a hose to the valve
- Run the hose to a drain point outside
- Open the valve to release the water
Never drain a hot cylinder while the water is still hot, as this can damage the tank and create a safety risk.
Step 5: Open Any Drain Valves in Your Plumbing System
Some homes have additional drain valves on pipework in areas such as lofts, airing cupboards, or utility rooms. If you find any, open them to help the remaining water flow out faster. You may need a bucket or container for this part if the valve doesn’t have a connection point for a hose.
Step 6: Use Gravity to Fully Empty the System
To ensure your plumbing system is completely drained, keep all taps open and allow gravity to pull the remaining water through the pipes. This can take a little time depending on your property’s layout.
During this process, walk through your home and check:
- Taps that might still be dripping
- Toilets that still have water in the cistern
- Pipes that may not have fully emptied
Step 7: Refill the System Safely When You’re Finished
Once your repairs, maintenance, or checks are complete, you’ll need to refill the system. To do that, follow the steps outlined below:
- Close all taps and drain valves
- Slowly reopen the mains stopcock
- Allow the system to fill gradually
- Open taps one at a time to release trapped air
- Recheck the toilets to ensure cisterns are filling properly
- Inspect the system for leaks
Opening the stopcock slowly prevents sudden pressure surges that can damage joints and connections.
Important Safety Tips
Draining your plumbing system is generally straightforward, but it must be done carefully to avoid unnecessary damage.
- Always allow hot water tanks to cool before draining
- Never force valves that are stuck, as they may break
- Use a hose for large volumes of water to avoid flooding
- Make sure you know which system you have (combi, vented, or unvented)
- Keep buckets and towels nearby in case of spills
- If you’re unsure about any step, seek professional assistance
If your plumbing system doesn’t drain fully or you suspect a blockage, you can always take advantage of a professional offering an efficient drain clearing service near you. They will help restore the proper flow of water and prevent damage to your system.
The Bottom Line
Knowing how to drain your plumbing system safely is an essential skill for every homeowner. Whether you’re carrying out repairs, protecting your pipes from freezing, or preparing for renovation work, following the correct steps will help prevent leaks, water damage, and unnecessary mess.
If you’re struggling to drain your system, dealing with a blockage, or noticing slow-running drains, you should consider hiring a professional who can handle the entire process on your behalf.
