Toilets can fail to flush for mechanical reasons that will vary depending on their design.
SIPHON TYPE
This type uses a lever arm to flush the toilet; this lever lifts the large diaphragm washer inside the siphon tube (see Chapter 1).
If the WC fails to flush, the first thing to do is simply to lift the lid from the cistern and check the operation of the linkage system used to lift up the diaphragm washer. Assuming this is OK, the fault will almost certainly be a split or worn-out diaphragm washer. This can easily be replaced but, with close-coupled WC suites, you have to remove the whole cistern from the wall in order to remove the siphon. There is a siphon design built as two parts, which allows you to pull the siphon apart to facilitate this repair, but unfortunately these are not commonplace. Toilet cisterns with flush pipes such as that shown in Figure 1.20 do not need to be removed from the wall.
To replace the washer, take these steps:
1 Turn off the water supply to the WC cistern – there may be a quarter-turn valve on the inlet supply pipe.
2 You now need to bail out the water from the cistern, using a sponge if necessary to draw out every remaining drop of water; otherwise what remains will discharge on to the floor when the siphon is removed.
3 For cisterns with a flush pipe, unwind the large nut securing it to the siphon, turning it anticlockwise.
4 Next, unwind the big nut securing the siphon to the cistern.
5 You can now lift the siphon from the body of the cistern.
To complete this action you will need to unhook the linkage to the lever arm and sometimes, if the arm of the float-operated valve gets in the way, you may need to remove this as well.
6 With the siphon removed from the cistern you can now see beneath the base of it and you’ll see the location of the old perished diaphragm washer.
7 Remove the hook attached to the top of the shaft that pulls the diaphragm; this then allows the diaphragm housing to drop from the base of the siphon (see Figure 4.15).
8 With the old washer removed, a replacement can be inserted.
You can buy them, if you are lucky to find one of the same size; however, I personally have always used thick plastic polythene sheeting and cut out my own, simply laying the old washer on the plastic as a template. The type of plastic you require is the type used as a damp-proof membrane or one of those heavy-duty plastic builder’s bags. When you get the old washer out, you will see the type of plastic I mean.
9 With the new washer cut, replace everything in the reverse order. All jointing washers should be in good condition, but where they have perished simply wrap some PTFE tape around the joining parts (not around the threads) where the old jointing washer or material was.
remove hook from top of siphon
replace PVC diaphragm washer
Figure 4.15 Replacing a WC siphon washer
10 Turn the water supply back on and test to see if it works.
Hopefully this has been another job well done!
ReMOvING A CLOSe-COUPLeD TOILeT CISTeRN
With a close-coupled toilet cistern there is, unfortunately, a little extra work to do before the siphon can be taken out: the cistern has to be physically removed from its location bolted to the WC pan. To do this, take these steps:
1 Turn off the water supply to the cistern and undo the pipe connection to the float-operated valve.
2 The overflow connection will also need to be disconnected.
If this is at the bottom of the cistern, only undo the nut that connects to the pipe going outside and do not entirely remove the internal plastic tube from the cistern, otherwise the water in the cistern will escape on to the floor.
3 Next, remove the two screws holding the cistern back to the wall.
4 Finally, remove the two wing nuts found beneath the cistern, one on either side of the back of the WC pan, holding the cistern down tight on to the pan itself. The cistern is now free to move and can be lifted from the pan.
5 Tip out the water from the still-full cistern into the WC pan.
6 With the cistern removed, you will see a big black foam washer pushed over the securing nut of the siphon, often referred to as a donut washer. Simply pull this off and replace it with a new one (which you can get from a plumbers’ merchant) when reassembling the WC after completing the repair.
7 Follow the procedure described above to remove the siphon and replace the washer.
8 Finally, reassemble the components in the reverse order.
In the unlikely event that you cannot obtain a new donut washer, it is possible to apply a large ring of ‘plumber’s mait’
(see Appendix 2: Glossary) as an alternative. However, if you use this, it is essential that the pan and cistern connecting
parts are absolutely dry, otherwise the plumber’s mait will not form a proper seal.
9 Turn on the water supply and test to see if it works.
VALVED TYPE
These flushing devices have only been installed since the turn of the twenty-first century and therefore are relatively new in the scheme of things (see Figure 1.8). When you operate the push-button mechanism to flush the cistern, the valve inside lifts up from its seating to allow the water to discharge directly into the cistern outlet. If the unit fails to flush, it is generally due to a broken component and, in most cases, the whole internal flushing valve will have to be replaced because spares for these devices are not generally available.
If you are lucky, you may be able to purchase an identical unit, making a replacement a relatively simple process. Looking at the new component, you will notice that there is a facility to turn and remove the valve from its base plate. So, once you have done this and removed the existing valve unit within the cistern, the damaged part can be replaced without the need to remove the cistern.
Remember to turn off the water supply before carrying out this task.