One-Armed Bandit - Mixer Tap Redesign

Introduction: One-Armed Bandit - Mixer Tap Redesign

About: Openproducts' focus is on design of new products and on innovative approaches towards improving existing products. An example: the CountClock, a concept facilitating children to learn telling the time. Purpose…

A single-lever mixer tap is robbing the user before his very eyes. Why? Its intuitive 'neutral' middle position is when the arm is directed towards the front; a lot of users do not realize that in this position actually medium temperature water is being supplied. Or even worse: as a result of the distance between the heating device and the tap (pipe losses) the warm water will never reach the user. The latter is mostly the case when only small amounts of water are being tapped.

This Instructable aims to highlight this design failure and suggests a redesign for the single handle mixer. The purpose is to reduce pointless energy use and consequently to save resources, not only in terms of energy carriers but likewise by reducing energy expenses. As the concept described is improving energy efficiency it can be qualified as Green Design.

This Instructable addresses three user groups:

1.) Designers of mixer taps: intuitive design should make sure that unintentional energy use is being avoided;

2.) Owners of public places and hotels: clients may unintentionally drive up energy expenses by not understanding or not being aware of the functioning of the single-lever mixer tap: user and cleaning person information might help here;

3.) Users of the mixer tap: by understanding the standard single-lever mixer tap it is possible to operate it appropriately and thus to reduce energy expenses.

Now what to do when you own such a mixer tap? Dependent on the type of users and in how far they are approachable (which varies significantly between a hotel-keeper and a parent) various options exist. As the pointless hot water demand of this badly-designed mixer tap might represent a significant share of the annual energy bill, the good news is that there are ways to improve on this:

A.) Replace the single-lever mixer tap by one with a more intuitive design, i.e. with the 'neutral' (i.e. cold water) position in the middle. This might be done by simply fixing the lever handle in a different position, twisted 45° clockwise (note however that this results in different tapping behaviour, see Step 3);

B.) Replace the single-lever mixer tap by a conventional mixer tap, which is more intuitive (but, indeed, also less comfortable and luxurious);

C.) Make sure that users better understand the functioning of the mixer tap. For this purpose banners have been added to this Instructable, stressing the fact that the middle position of the mixer arm involves energy use that might not be needed. The source file of this banner is available on request (PM), see Step 4.

Note that this instructable aims at addressing awareness of the possible unintentional energy use involved in using a badly-designed single-armed mixer tap. It doesn't feature a practical manual on how to execute the redesign as shown in the pictures, since implementing this redesign requires a custom-made approach.

Another Openproducts' Instructable that focuses on energy saving in hot water preparation is Energy Saving by Omitting Stand-By Energy Use in Combi Boiler through Remote Switches.

Step 1: Standard Single-Lever Mixer Tap

The standard situation for a single-lever mixer tap is to get cold water when the lever handle is completely turned right, and hot water when the lever handle is completely turned left (I have seen quite a number of mixer taps that have been connected the other way round, one can imagine the wasting of energy resulting from this careless work). Temperature measurements have shown that the middle position gives quite precisely the average of the cold and hot water temperature.

The next step shows that it is possible to fix the lever handle in a different position, twisted 45° clockwise. Doing so, the middle position of the lever handle will provide cold water only.

Step 2: Adjusting the Lever Handle

The lever handle can be removed. You'll find a screw, possibly closely under the lever or maybe at its backside, often hidden behind a rubber plug. Unscrew it and remove the lever. See whether it is possible to fix the lever in a different position. This might require some filing or other non-reversible modifications. If it is not possible to adjust the lever handle, you always can refer to Step 4, the improved user information.

The next step shows that after succesful modding the lever handle behaviour has changed significantly.

Step 3: Different Lever Handle Behavior

From the picture it can be seen that after the modding the lever handle deviates to the left when lifting it, starting from its middle position. This is a feature of the redesign; it will remind you to the successful mixer tap tweak.

Step 4: User Information Banner for a Standard Single-Lever Mixer Tap

The pictures show a banner for printing on paper and sticking close to a standard single-lever mixer tap. The purpose is to make the user realize that the middle lever handle position involves energy use, which might not be fit for purpose. The source file of the banner is also available on request by PM (in OpenDocument Graphics .odg). Feel free to post alternative or translated versions as a comment to this Instructable.

Step 5: License

This Instructable is made available through a Creative Commons Attribution (cc-by) license. Republishing this Instructable is allowed, provided it is being attributed properly (cite the name openproducts, link to,, or the original Instructable. For other arrangements send a Private Message through the instructables member page (

As explained in the beginning, the concept may be useful for various target groups, which may benefit from reduced energy expenses. It would be great if this redesigned single-lever mixer tap would benefit from an uptake by the installers.

If this design infringes any rights then refer to Article 28 in the Terms of Service (

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