Automatic Hygiene Flush: Function, Technology, and Use in Public Facilities
Five weeks of school holidays. The changing rooms are empty. Water stands in the pipes and fittings—warm enough to provide an ideal environment for Legionella.
In public buildings, sports facilities, hospitals, and schools, this scenario is commonplace. Automatic hygiene flushing is the technical answer: a built-in function that ensures stagnant water is periodically replaced without human intervention.
Why Stagnant Water is a Problem
Legionella are bacteria that naturally occur in water bodies and drinking water systems. It becomes critical when they can multiply unhindered in a hot water pipe or fitting. The optimal growth window is between 25 and 45 °C—exactly the range in which pre-mixed water sits when it doesn't flow for hours.
When showering or operating the faucet, water contaminated with Legionella can be inhaled as an aerosol. The risk is real; the health consequences for sensitive groups can be severe.
The SVGW guideline W3/E3.1 sets clear requirements for drinking water installations in Switzerland: stagnation should be avoided during planning. For systems where periods of inactivity are unavoidable due to construction or operation, an active measure—automatic hygiene flushing—is recommended.
| Tip: Keep cold water below 20 °C, hot water above 55 °C—and consistently avoid stagnation. Hygiene flushing secures the system even with irregular use. |
How Hygiene Flushing Works
The control unit in the fitting monitors the idle time. If the fitting is not used for a defined period, the control automatically triggers a short flush—the stagnant water is replaced by fresh tap water. Typical intervals are 6 or 24 hours after the last activation, depending on the product and installation situation.
The setting is factory-set for many products. It is crucial to adjust the interval to the actual frequency of use of the system: a 6-hour interval also protects during short overnight breaks, while a 24-hour interval is sufficient for systems with regular weekend operation.
Where Hygiene Flushing is Used
Washbasin Fittings
In washrooms of schools, office buildings, or public facilities, water typically stands still overnight and on weekends. Fittings with integrated piezo electronics are directly equipped with automatic hygiene flushing.
The ASA-SLU 92NP stainless steel washbasin fitting (CHF 715.—) combines piezo activation, adjustable water flow time (2 to 62 sec.), and hygiene flushing in a vandal-proof stainless steel housing. Connection to cold and hot water, temperature regulation via integrated mixer.
Urinals
Urinals in schools or sports facilities are not used at night, on weekends, or during holidays. Without hygiene flushing, the water in the inlet stands still for hours.
The ASA-SLPN 07C urinal (CHF 2,150.—) triggers hygiene flushing after 6 hours of inactivity. The vandal-proof stainless steel construction with 24 V DC is designed for heavily used public sanitary facilities.
For facilities without high vandalism requirements, ceramic urinals with integrated radar flushing are available—such as the Laufen Caprino with ASA-SLP 23B (CHF 1,110.—), which also flushes automatically after 6 hours.
Showers
In changing rooms and fitness centers, the idle time for showers is particularly critical: the hot water portion in the pipe section before the shower control cools down to critical temperatures when not in use.
For simple connections to cold or pre-mixed water, the ASA-SLS 01PA concealed shower control (CHF 490.—) is suitable: piezo-controlled, concealed mounting, integrated hygiene flushing.
If you want to allow the user free temperature selection, choose the ASA-SLS 02P (24 V DC, CHF 554.—) or the battery-operated ASA-SLS 02PB (6 V, CHF 667.—): integrated temperature rotary knob, continuously adjustable, piezo activation, and automatic hygiene flushing.
What to Consider in Planning
The flushing interval should be adapted to the actual frequency of use. In schools with six-week summer holidays, a 6-hour interval also covers short periods of non-use. In buildings with regular weekend operation, a 24-hour interval may be sufficient.
For battery-operated systems (6 V), the flushing frequency is also a factor for the operating time: more frequent flushing shortens service intervals. Electrically connected variants (24 V DC) offer more leeway here.
| Tip: Automatic hygiene flushing does not replace the periodic checking of water temperatures according to SVGW W3/E3.1. It is a supplementary technical measure—and a standard planning requirement in public facilities with interrupted use today. |
Conclusion
Automatic hygiene flushing is not a comfort option. In public sanitary facilities with regular periods of inactivity—schools, hospitals, changing rooms, hotels—it is an active contribution to Legionella prevention. The control operates automatically, regardless of user behavior—and for every type of fitting: washbasin, urinal, and shower.
Are you planning a project or do you have questions? We would be happy to advise you—by phone at +41 44 825 62 62 or by email at info@armatron.ch.
