If the cistern of your toilet is leaking into the pan, and the leak is not too substantial, it can be difficult to detect. It will be leaking 24/7 though and as such can waste a surprising amount of potable water, which is a waste of resources, but also a waste of your money. This article will give you an idea of how to check and what to do about it if you do find a leak.
The Test
Remove the top of your toilet cistern and add a few drops of food colouring dye, just enough to give a discernible tint to the water in the cistern, and leave it for an hour or so without flushing. If you have a leak and it is a bad one, the colour will appear in the pan almost immediately, but if it is a very slow leak it may take a bit of time, hence leaving the system for an hour. If there is no obvious tint to the water in the pan after an hour you will be pretty right.
Having said that, things can change over time, so you should do this test every year or two so you can keep on top of things. If you suspect a leak (eg your water bill has gone up without any obvious changes) you should do the test right away just to make sure.
What You Can Do
The fix will vary slightly, depending on the brand of toilet you have, we have a “Caroma” brand. The most important thing is to get spare parts which are designed for use with your brand of toilet. They may look the same on the face of it, but unless the packaging states the parts are for your brand of toilet, you should not buy them. I picked up a part recently for an issue we had, the front of the part looked exactly the same as the one from our toilet, but when I bought it and removed it from the packaging the back looked somewhat different. It was not labelled as fitting our toilet.
Left: original seal Centre: new repalcement seal (correct) Right: New seal which llok OK from the front but rear was totally different
With more hope than confidence I fitted the part, but sure enough it didn’t work: wasting the part (I couldn’t return it), a small amount of money, my time and the hassle of driving out to find the correct part. Another one of life’s lessons learnt!
In my experience the leak is most likely to come from one of two places – The flush valve washer or the inlet valve head seat diaphragm.
Remove the top of the cistern and have a look in, if there is water going over the internal overflow pipe it’s probably the head seat diaphragm, if water is still getting into the pan but the overflow is dry it is likely to be the flush valve washer.
The view inside our cistern - white structure on the left is the inlet, open tube in the middles is the internal overflow and the cylinder on the right is the dual flush mechanism.
The flush valve washer seals at the bottom of the (in our case) dual flush mechanism to prevent water getting to the pan once the flush is completed. To fix it is just a case of flushing the toilet to remove the water and then turning off the water inlet at the tap. Then grasp the mechanism tower and twist it slightly to the left and lift it up out of the cistern. The washer is at the bottom of the tower, remove the old one and replace with a new one. Place the tower back into the cistern and twist slightly to the right to seat it. Turn on the fill tap and away you go.
The orange flush valve washer at the base of the dual flush mechanism
To replace the inlet valve headseal, again, empty the cistern and turn off the inlet tap, grab the attachment arm on the side of the mechanism and disconnect it, twist the housing to the right and remove it from the cistern. Pull out the headseal and replace with a suitable spare. Place the housing back onto the mechanism and twist to the right to re-seal, and reconnect the lever. (Here is a video from Caroma which makes the process a bit clearer!)
Inlet valve head seal - the old one, showing that the seal has come completely off the support fitting.
New inlet valve headseal in place and about to be refitted into the cistern
As mentioned earlier, this might not totally fit your cistern if it is a different type to Caroma, but it will give you an idea of where to look for the problem. Good luck!
