How to Replace the Cistern Valve in a Dual Flush Toilet

What You'll Need
Towels (to soak up water)
Pen (or tape for marking water level)
Liter Bottle
Replacement Cistern Valve

A dual flush toilet is a regular toilet that actually uses two buttons to flush different levels of water. One is for a full flush while the other is for a half flush. It saves up to 67% of water usage in homes cutting it almost in half. The dual flush toilet is more expensive than other low-flow type toilets. Kits can be purchased at a hardware store to convert a regular single flush toilet to a dual flush toilet. These can be self installed with a little plumbing experience.

A cistern will use about 6 liters for a full flush or 3 for a half flush. The cistern valve reduces the height of the water in the actual cistern. This reduced the amount of water used. These valves can easily get worn and may need to be replaced. If you are not able to do a self install for the replacement valve, call in to a plumber. If the cistern itself is too old, it is probably a little more cost efficient to replace the entire cistern with a dual flush unit. There are a few steps and tools listed below to help you replace the cistern valve in a dual flush toilet.

Step 1 – Purchasing the Replacement Dual Flush Cistern Valve

Write down the make and model of your existing cistern (or take a picture of it) and take it to your local hardware store. This will ensure that the right replacement valve is purchased. Large hardware stores may have the valve on hand. The smaller hardware stores may have to order it for you. If you do this replacement yourself, be sure to read the instructions thoroughly.

Step 2 – Adjusting the Flush

Lay down towels to soak up the water that will be on the floor. This may be about several liters.

Step 3 – Cleaning the Cistern

There may be some sediment built up in the cistern from years of tap water running through it, so this will need to be cleaned out.

Step 4 – Removing the Existing Valve

There are two clips on the back of the valve, and two clips on the front. Unclip all four of them and the valve will pop straight out. You can lift the valve up to remove it.

Step 5 – Installing the Replacement Cistern Valve

Set the replacement valve back into place where the previous one was removed. Snap the two clips on the back of the valve, then snap the two clips on the front. 

Step 6 – Check the Valve

After the cistern valve has been replaced, check the amount of water it uses. It can be adjusted if you want the full flush reduced. The half flush will then be able to be adjusted. 

Step 7 – Adjusting the Half Flush

Mark the water level using a waterproof pen or a piece of tape. Turn off the water to the cistern and press the half flush. This should drop the water level to about 1/3 to 1/2 of the way to the top. Mark this level also. The measuring jug can now be used to refill the cistern full. After counting the amount of liters it took to fill, adjust the half flush so that it will produce 3 liters of water.