How to Convert to a Dual-Flush Toilet

Someone pushing a button to flush a toilet.

As California looks likely to return to drought status, water usage is once again high on the list of environmental concerns. It has been calculated that the average Californian uses over 200 gallons of water per day. If we reduce the water consumption a little per person, then this will potentially have a dramatic effect. Of course, it’s not just California—the average water usage across the country is still over 80 gallons a day per person.

One practical way of helping in water conservation is to reduce the amount of water that the toilet uses when flushing. However, the waste still needs to make to the sewer, so a one-size fits-all reduction of water usage by the toilet doesn't necessarily work. In the past, it was recommended to put a brick in the tank to reduce its water capacity. This is a bad move, unless you're in the drain unblocking business.

A greater volume of water from the tank is needed to push solid waste into the drains and sewer system. However, for the majority of time, a much smaller volume of water is required to flush the drains through and it's here that we should be looking to reduce the volume of water used to flush the toilet. This brings me neatly onto the dual flush toilet and how to convert your single flusher, thus saving you and the environment in the process. OK, that final line might be over dramatic, but we all need to do what we can, right?

How Much Are the Water Savings?

Water splashing against a white background.

Based on four people living in a house with two bathrooms, each flushing five times a day, the saving over a post-1994 toilet (1.6 gallon tank) equates to around 7,000 gallons of water in 12 months. This is a significant amount per household.

This change is relatively straightforward and little plumbing or DIY experience is required. The dual flush kit costs around $30 each and should be fitted to each toilet in the house if you would like to maximize your water-saving efforts. The assumptions here are that you have a lever flush on a close coupled toilet as this is the most awkward arrangement to work on. Simply tailor the instruction accordingly if you have a different set-up.

The Tutorial

The inside of toilet tank.

The humble toilet consists of a bowl (the bottom part) and a tank (the top part). For this article, we need to focus on what's in the tank. The intake valve / ballcock / flushing mechanism looks at first glance to be a bit complicated, and this is connected to the handle or button. At the bottom of this mechanism is a flapper, which allows the water into the bowl when the handle is pulled or the button is pushed.

Step 1

Stop the tank from being able to fill up with water by closing the isolation valve from the water system. There should be a tap close to the tank that turns clockwise. Otherwise, you'll need to turn off the water supply at the main feed coming into the house. Flush the toilet to empty out the water from the tank. Remove the tank lid (careful—they are often heavier than they look) and set it aside somewhere safe.

Step 2

Remove the link between the flush lever and the internals of the tank; you may need some long nose pliers for this. Remove the nut holding the lever in place and remove the lever. Use a towel to soak up any outstanding water in the tank (you want to keep the floor as dry as possible).

Step 3

Usually there are two screws holding the tank to the bowl. On the bottom side of these should be some wing nuts which are usually plastic. These need to be undone. You may need to use a screwdriver on the top of the screw to stop it rotating while you undo the nut. Repeat for the second nut and set aside.

Step 4

If there are any screws holding the tank to the wall, these should be removed and stored safely. The tank should now lift away from the bowl and be placed on its back where you can work on it further, so a clean workbench would be perfect. Examine the bowl for any seals or washers that sit between the tank and bowl that will need to be reused, unless they are being replaced.

Step 4

On examining the tank, you should see how the flushing mechanism is held in place. This is usually via a plastic nut which can then be carefully undone using grips if required. Check to make sure that there is no calcium buildup or dirt where the new mechanism will go. I'd also check that any washers are still in serviceable condition. If in doubt, replace them now as its easier to do while the system is apart.

Step 5

Fit the new dual flush unit into the hole, ensuring that you have a watertight seal. Tighten the nuts so that they are finger-tight. Slowly ease the tank back onto the bowl. Ensure that the foam or rubber seal that interfaces between the tank and bowl is still in the right place. Once stable, tighten up the wing nuts holding the two units together. Use grips if unsure, but don't overtighten and crack the nut.

Step 6

Place the new button into the existing hole where the lever was. Connect and tighten the nut to hold in place.

Step 7

Turn the water back on. Check for any leaks. Once happy, push the buttons to make sure that everything is OK, of course allowing for the tank to fill up between actions. Replace the tank lid carefully.