How to make on older toilet use less water

There’s a simple way to make a non dual flush toilet use less water without permanently modifying it. It only takes 30 minutes, costs virtually nothing and should save an average Australian household around $70 a year and 50 litres of water a day.

First, check how much water the toilet uses per flush. This can be done in one of two ways:

  • Use your water meter to measure how much water the toilet needs to refill after a full flush (provided that no other water is being used whilst you’re doing this measurement).

OR

  • Carefully remove the cistern lid (where the water is stored for the next flush), turn off the tap that supplies water to the toilet, and make a note of where the water level is in the cistern.
  • Flush the toilet and then use a jug or bucket to refill the cistern back to the same level. Note how many litres were used.
  • Some cistern lids may slide off easily whilst others may require you to unscrew a fitting first (usually located where the flush button is) before the lid can be gently removed.

If your toilet uses more than 6 litres for a full flush, here’s how to make it use less:

 

Overhead view of toilet with cistern lid removed
Cistern lid off: bottles can go on the left away from the flushing mechanism and ball valve.

 

  • Gently take the cistern lid off if you haven’t done so already.
  • Take a few bottles, fill them with some sand/gravel, top them off with water, seal them and place them inside the cistern where they won’t interfere with the toilet’s ball valve or flushing mechanism.
  • Every litre of bottled water/sand/gravel that you add to the cistern reduces its flushing capacity by a litre so for a 12 litre per flush toilet you would add 6 litres of bottles.
  • Although 6 litres a flush is overkill for flushing liquids, it’s not advisable to go lower than this as you will need it to flush solids.
  • Keep in mind that some older toilets are not designed to flush with smaller amounts of water (e.g. you shouldn’t have to flush multiple times to remove solids).
  • Don’t use materials like bricks which can dissolve and block up parts of the toilet.

This idea has been tested in a former rental property and it worked very well while we have seen similar reports from others online. As a renter, it is a great way to save water if you can’t put in a water saving toilet.

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