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How to plumb yourself out of trouble

Difficulty rating: Medium

These tasks may be tricky so will suit you if you're experienced in DIY, or simply love a challenge.

Before you get started on any of our 'how to' guides, please take a moment to read through our DIY safety tips.

Tools for the job

 1. Turning off the water supply

  • With most plumbing jobs you need to turn off the water supply. The easiest way is to use an isolator valve on the water pipe to an individual appliance (fig. 1). If there's one on the appliance you're working on, turn the valve to 'off' with the screw on top of the valve. Or this may be a tap on some isolator valves as in fig. 1.
  • If there's no isolator valve, turn off your main stopcock. This is a brass tap fitted on your pipe work. It's normally in the kitchen or wherever the mains water enters your home (fig. 2).
  • As a last resort, turn off the water at the water company's valve under the cover outside your house (fig 3). For this job you'll need a special long-handled spanner. You can buy one from plumbers' merchants.
  • Once the water's turned off, open the taps on your sink until the water stops running.
There may be an isolator valve on the water supply pipe. Turn this off.
Figure 1
If there's no isolator valve, shut off the water at the main stopcock
Figure 2

2. Changing the tap washer

  • Make sure the system you're working on is isolated and drained down. For example, drain down the hot water system if you're changing a washer on a hot tap.
  • Use a flat head screwdriver to lever off the hot or cold indicator cap on the tap. Once you've removed the cover, you'll see a screw that holds the handle of the tap in place. Remove this screw and then the handle from the tap.
  • When you've taken off the handle, you'll see a valve. With an adjustable spanner remove the body of the valve by unscrewing it anti-clockwise.
  • Remove the screw from the bottom of the valve that holds the washer in place. Replace with the new washer. Tighten the screw back into position.
  • Screw the valve back into the tap and use an adjustable spanner to make sure that the valve is tight.
  • Screw the tap handle into position and replace the red/blue indicator cap.
  • Refill the system you were working on and check for leaks.


Helpful hint...

Plumbing involving pipework is covered by a number of safety regulations. If you're unsure about them, talk to a professional plumber.


3. Unblocking a waste trap

  • There are a few different types of waste traps. The most common are the 'S', 'P' and 'shower' traps. They're all pretty similar and can be disconnected by removing the large nuts at the top and bottom of the trap to release them. Figs. 4 and 5 show how to disconnect an 'S' trap.
  • Put a large bucket underneath the trap to catch any discharge (fig. 4). Unscrew the nuts.
  • To unblock the waste pipe, remove the trap and clear the blockage into the bucket (fig. 5).
  • Check the rubber washers are in place and reconnect the trap back into position.
  • Finally, pass some water through the waste trap and check for leaks.

4. Changing a ball valve

  • Ball valves control the level of water in your cold water tank (which is usually in your loft). They can seize up over time. If the overflow pipe on the tank has water dripping or flowing from it, it's a sign that your ball valve might need changing.
  • Firstly, shut off the mains water stopcock to stop the water flow to the ball valve.
  • Undo the nut connecting the supply pipe to the ball valve body (fig. 6).
  • There are two big nuts on the ball valve, either side of the tank wall, that hold the ball valve in place. Unscrew the back nut on the outside of the tank. You can then remove the ball valve.
  • Fit the new ball valve and screw on the back nut. Make sure the ball valve is secure by tightening the back nut with a pair of grips (fig. 7).
  • Replace the washer on the nut connection (the nut on the supply pipe) and tighten it.
  • Finally, turn on the mains stopcock and make sure there are no leaks.


Helpful hint...

Don't overtighten compression fittings. If you tighten them too much you might damage the internal seal and cause them to leak.

Undo the nut connecting the supply pipe to the body of the ball valve on your cold water tank.
Figure 6
Fit the new ball valve and screw on the back nut. Secure it by tightening the back nut with a pair of grips.
Figure 7

5. Changing a stopcock

  • A stopcock isolates your mains water supply. It's a red turning handle (fig. 2) and is usually in your kitchen or where the mains water supply enters your house. Sometimes a stopcock can seize up and become impossible to turn off. In this case you must always replace it.
  • Firstly, isolate the water supply to your home by shutting off the water company's valve that's located in the street (fig. 3).
  • You should find this valve underground, beneath a lid indicating it's the water box. Lift this lid with a flat head screwdriver and shut off the stopcock. If you can't find your stopcock, contact your water company for help.
  • Make sure the water supply is off by opening a mains pressure-fed tap (normally a kitchen tap) until there's no water flowing from it.
  • Open both nuts on the stopcock and remove the stopcock body followed by the washers (or 'olives'). You may need to cut through the old washers with a junior hacksaw if they won't come off. But make sure you don't cut the pipe.
  • Before installing the new stopcock, have a look on the body - you should see an arrow. This arrow must face the direction that the water flows into the house when you install the stopcock.
  • Place both sets of nuts and olives over the pipes and add a bit of sealant paste around the olives.
  • Put the stopcock's body in place and tighten the nuts with a pair of grips. Use one grip to hold the body of the stopcock and the other to tighten the nuts.
  • Turn the water supply back on and check for leaks.

6. Fitting self cutting valves

  • f hot and cold connecting valves aren't fitted on your pipes, fit self-cutting valves whenever you do plumbing work around an appliance like a washing machine.
  • These come as a kit and can be attached to 15mm copper water pipes without having to turn off the water supply.
  • Choose a good spot on a section of your cold water supply pipe near to the appliance it connects to.
  • Fix the back plate of the valve directly behind the pipe. The top piece is placed over this and the parts screwed together around the pipe.
  • Turn the valve to 'off' and screw it into the pipework. This will make a small hole in the copper pipe. Use two spanners to tighten the valve nuts.
  • Screw one end of the flexible plastic hose connector to the end of the valve and the other end to your appliance.
  • Repeat these steps for the hot water supply if your appliance needs cold and hot water.
  • Finally, turn on the appliance to check nothing leaks.


Helpful hint...

When doing DIY in or around your kitchen sink, bath or basin, leave the plug in to stop dust and debris blocking the pipework.

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