We expect, even take it for granted, that washrooms should be smooth-running, hygienic environments. At the same time, we naturally feel that human involvement in them should be kept to a minimum. The character of the washroom attendant, as employed by exclusive bars and restaurants, is an almost titillating throwback to long-vanished notions of personal service.

The typical washroom functions as an almost completely autonomous space. Cleaners and maintenance workers are seen as infrequently as possible. Ideally, the place runs itself. What specifically, though, are the roles played by automation in its design and operation?

Cleanliness is the obvious priority. There are automatic public toilets that fully self-clean after every use, even using high-pressure washers on the walls. Washrooms by their very nature are more complicated.

Where cleaning is intermittent, the reduction of physical contact with common surfaces is a key principle. The idea behind a public toilet’s labyrinth, or doorless, entrance is that visitors can come and go without touching a germ-covered door handle.

Hence the importance of motion (usually passive infrared) sensors in the washroom. Lights may be activated, taps turned on and off and hands dried all without the fixtures having to be touched. There are even toilet paper dispensers that use the technology.

Motion sensors used to activate the flushing of urinals have the added benefit of cutting down on undue water consumption. In the UK, following the Water Supply Regulations 1999, the water filling a cistern serving a single urinal should not exceed 10 litres per hour (7.5 per urinal for a cistern serving two or more). This is a threshold that the old 24/7 flushing systems could easily exceed if the refill rate (determined by the pet cock valve) was too fast or the timer’s setting too frequent.

On a person’s approach, the motion sensor activates a time-delayed signal to a solenoid valve which opens to begin filling a cistern with water. Once full, the cistern flushes the urinal and the valve is automatically closed. Long periods of inactivity will also trigger a hygiene flush.

This arrangement brings a more precise degree of control to water management than the simpler hydraulic valve system. Here cisterns are filled in response to short-term drops in pressure within the water supply. Flushing toilets and running taps, that is to say, are the approximate indicators that a washroom is being used and are thus tied to urinal flushing times.

Washrooms that reduce the flow of water through their urinals may find, especially in hard water areas, a greater incidence of limescale build up. With more time to evaporate between flushes, mineral-rich water will leave greater deposits of calcium carbonate. These, combined with uric acid, encourage the growth of bacteria, create unpleasant smells and can ultimately block urinal pipework.

One way of combating this problem is to integrate specific treatments into the flushing system. Technology company CBio, for example, has developed a product that is automatically dosed into the cistern with every flush. Such products rely on microbial and enzyme activity actively to break down the scale and establish bacteria that naturally combat odours.

Both reduced water usage and a greater reliance on biological cleaning agents illustrate ways in which the modern washroom aims to function on a more environmentally-friendly level than previously. This in part reflects developments in legislation, such as the growing insistence in EU regulations on rapid degradability for surfactants, an active ingredient in a range of detergents.

There are urinals, in fact, that use no water at all. Following a 2016 water-saving ruling in drought-hit California, waterless urinals were installed in a number of public venues. These have generally depended on replaceable cartridges containing liquid sealant to sit over the drain and prevent back up of odours. Alternative systems use biological blocks and require occasional sluicing.

The chances are that more and more washrooms will combine this kind of environmentally-friendly, biological approach to cleaning with a sensor-based control of water use where necessary. Also likely to become more widespread is the use of sensors to monitor activity and consumption levels as an aid to cleaning and maintenance routines.

Less certain, perhaps, is the future of the automatic sit-down toilet. Conspicuously high-tech models, such as those manufactured by leading Japanese company Toto, unite toilet, bidet and drying functions and for reasons of expense have an obviously limited distribution.

But what of the more functional washroom type? Toilets that use simple motion sensors to decide when to flush (these may be active infrared, rather than passive, with a temporary interruption of the beam associated with occupancy of the seat) are also far from widespread. Where they are found, however, such as in parts of the USA, so too is a measure of public unhappiness about them.

Unexpected flushing (or worse: not flushing) is the bane of many users’ experiences. Whether due to less than clean sensors or misunderstood positional behaviour on the part of users, universally accurate flushing seems yet to have arrived in this area of the washroom. Talk of covering sensors over with post-it notes is common.

Even assuming the technical issues are resolvable, though, there remains a more philosophical question. To what extent are people comfortable allowing automation into the most intimate areas of their lives? After all, attending to our own cleanliness is about as basic as it gets. What about a sort of baseline responsibility, or personal agency?

The answers may vary from one culture to another, as they may over time into the future. But for now, for some, if automation has such a thing as natural frontiers, this may be one of them.