Install a dual flush toilet cistern outlet valve to save water

Introduction

The Smart Apartment is not all electronics. Some smart ideas are mechanical. The dual flush toilet cistern is one of these. You can save a considerable amount of water to help the environment (and perhaps save some money) with a properly installed unit. These units have two buttons: one for a full flush and one for half, as required by the user. Dual flush units have been required under Australian planning regulations for some years. But older houses will not have them, or yours may not be properly adjusted. You can buy a kit at the hardware store to convert an old single flush toilet to dual flush and install itself yourself (regulations and ability permitting) or have a plumber fit one.

An old cistern will use about twelve liters of water per flush. A modern unit will use six liters for a full flush or three for a half flush. There are more advanced units using four and a half liters for a full flush but these still use three liters for a half flush.

A kit for an old cistern will add a three liter half flush. This will not reduce the amount of water used for the full flush. You can also adjust the inlet cistern valve to reduce the height of the water in the cistern and so reduce the amount of water used. But you can't reduce it by more than about three liters (bringing it down to nine liters) as old toilets are not designed to work with less water.

Measuring how much water your toilet uses

You can measure the amount of water your toilet uses:

1. Remove the lid from the cistern: You may need to unscrew the flush button to remove the lid. Be careful not to drop the lid as it may be slippery.
2. Mark the full level: Use a waterproof pen or piece of tape to mark the water level inside the side of the cistern (or measure the level from the top).
3. Turn off water to the cistern: There should be a tap located under the cistern. Otherwise you will have to turn off the mains water to the home to do this.
4. Press flush: Let the cistern empty.
5. Fill from a measuring jug: Use a bottle of know size (such as one liter) to refill the cistern with tap water to the full mark. Count the number of liters to fill (measure to the half liter is close enough).

Installing a dual flush cistern outlet valve

Make a note of the brand and model of your cistern. This may be written inside or under the unit. Also it may help to take a photo of the inside workings so that if something goes wrong later you can put it back together.

Take the details to a hardware store and obtain a dual flush replacement. Large hardware stores, such as Bunnings and Hardware House have units in stock, small stores may need to order a unit. Make sure you can return the unit as it may not fit. Note that it is an outlet valve you want, not an inlet valve. An example is the "Fix-A-Loo" brand "Hush Flush" cistern outlet valve.

If you are not confident to install the valve yourself (or local regulations do not permit it), then call a plumber. If you cistern is very old, it may be more cost effective to replace the whole cistern with a dual flush unit.

Third party units, such as the Fix-A-Loo have several adjustments to suit a wide range of cisterns and to adapt single to dual flush toilets. As a result they are complex looking (but like a modern sculpture). Read through the instructions and examine the photos supplied before attempting installation.

You are going to end up with several liters of water on the floor, so take precautions to soak it up. The bottom of the cistern may have some sediment in it accumulated from years of tap water, so you might want to clean it out.

After installing the unit as per the instructions, you need to check the amount of water it uses. Adjust the inlet valve if you want to reduce the full flush (you might find nine liters the practical limit). Then adjust the half flush.

To adjust the half flush:

1. Mark the full level: As before, using a waterproof pen or piece of tape, mark the water level inside the side of the cistern.
2. Turn off water to the cistern: There should be a tap located under the cistern. Otherwise you will have to turn off the mains water to the home to do this.
3. Press half flush: The water level in the cistern should drop about one third to half way. Mark or measure this level.
4. Fill from a measuring jug: As before, use a bottle of know size (such as one liter) to refill the cistern with tap water to the full mark. Count the number of liters to fill (measure to the half liter is close enough). Adjust the half flush unit to provide about three liters of water.