How to repair a WC flush system

Making sure your toilet is working properly and not wasting water will help you save money in the long run. Read how to identify the cause and fix the problem with leaky loos here.

Level of difficulty

Level 2: Intermediate

What you need

• Wrench
• Rag
• Ball valve
• Tape
• String
• Pliers
• Lubricant oil
• Screwdriver
• Chisel
• Washer slide
• Portsmouth valve/Diaphragm
• Plastic adapter
• Banded couplings

The steps to follow

Fixing a faulty ball valve

1. Ball valves control the flow of water into toilet cisterns. They wear out and cause an overflow from the cistern's warning pipe or may result in the cistern running dry, which causes the cistern to not flush properly.
2. If you spot water overflowing from the cistern, check to see if the valve's float is actually floating. If it is partially submerged, tie the ball valve with a string or tape it to side to shut off the valve.
3. Otherwise, unscrew the float and empty the water.
4. For a temporary solution, you can tie a small plastic bag tightly around the area where the existing ball valve was attached. You'll need to replace with a new float as soon as possible. Make sure you know which type to get. The most commonly used valve is the brass Portsmouth with an internal piston. Other types include equilibrium or diaphragm valves.
5. Turn off the main water supply to the cistern.
6. If the fault is in the toilet cistern, cut off the supply to the cold water storage tank, drain it by opening the bathroom cold taps and flush the cistern.
7. If your toilet has a Portsmouth valve, remove the float arm and pull out the securing pin with pliers.
8. Unscrew the cap at the end of the valve with a wrench. Apply some lubricant oil to loosen it.
9. Lever out the piston by sliding the blade of the screwdriver in the slot of the valve. For a one-piece piston, simply remove the old washer and replace with a new one. If you have a two-piece piston, rotate the piston and unscrew the cap with a screwdriver to remove the washer. Replace with a new washer.
10. Clean the valve parts, and lubricate the piston with a little lubricant oil.
11. Reassemble the valve and turn the main water supply back on.
12. Make sure that the cistern fills up just below the warning level.
13. For diaphragm valves, unscrew the retaining nut at the end of the valve body and remove the end cap.
14. Lever out the existing diaphragm with a screwdriver and replace with a new one. Note the way in which the old diaphragm was fitted so that you can insert the new one in the same way.
15. Reassemble the valve and turn on the water supply.

Repair your toilet  siphon

Note:
When you flush the toilet, the toilet's siphon lifts a plate upward from the lower part of the siphon. The flap valve (a flexible plastic diaphragm at the top of the plate) shuts the perforation for the plate to act as a piston. It then carries water to the cistern to start the flushing cycle. As the water enters the cistern, pressure will start pushing the diaphragm away from the plate. The plate will resume to its original position as the water continues to flow. The float will fall when the cistern empties, which will open the valve and refill the cistern. A new diaphragm will need to be fitted if the existing one breaks in the siphon.

1. Remove the cistern lid and turn off the service valve on the supply pipe. Otherwise tie the ball valve arm up to the side of the cistern. Flush the cistern to empty it.
2. Check for the type of siphon unit that is used. If the top part is secured with a knurled connector, separate the flap valve from the flush pipe without disconnecting the latter from the cistern. Unhook the C-ring from the siphon, undo the connectors or locking pin and slide the valve up and out of the cistern.
3. Slide the lift rod and plate out of the bottom of the siphon unit to remove the old diaphragm and replace with a new one. Reassemble the siphon and restore the water.
4. Disconnect the flush pipe if you have a one-piece siphon unit. Undo the nut holding the siphon flush pipe to the cistern.
5. Have a bucket handy to collect any remaining water in the cistern. Lift and remove the whole siphon unit out and replace the diaphragm.
6. For close-coupled toilet units, you'll need to lift the cistern off the wall.
   
   a. Undo all supply and overflow pipe connections.
   b. Remove any fixings holding the cistern to the wall.
   c. Lift the cistern, unhook the lift rod and invert the cistern to remove the siphon.
   d. Replace the new diaphragm.
   e. Place the cistern against the wall and tighten all fixings.
   f. Reconnect all supply and overflow pipe connections by screwing plastic adapters or banded couplings onto the pipes.

Related articles

• How to fix a blocked loo
• How to repair an overflowing cistern

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