Cover story

a day and a leak in a cistern-flush toilet is very difficult to detect.³ The resulting maintenance is time consuming and problematic, especially where cisterns are installed on frame systems behind IPS panels. However, with a direct flush system, any leak is very easy to identify and remedy.

Direct flush mechanisms, designed for public washrooms, are much more robust. The hydraulic timing mechanism on Delabie’s Tempoflux range of direct flush valves relies on water pressure to operate.

A self-cleaning timing groove reduces maintenance and extends the operational lifespan to over 500,000 activations. Furthermore, the mechanism has standard replacement parts that are easy to access and exchange, simply by isolating the water supply via an integrated stopcock.

Challenging perceptions Contrary to popular belief, direct flush toilets can replace cistern-flush toilets in refurbishment projects. If the header pipe is close to the installation, only the branch pipe run needs to be changed in the majority of cases.

Although the methodology for calculating pipe sizes for cistern-flush is different to that for direct flush, the pipework sizing is similar due to the principle of calculating simultaneous use. A direct flush valve activates for seven seconds, whereas cistern refill is between 40 and 60 seconds. Although the effect on demand is cumulative, the shorter duration of the direct flush means that in effect fewer valves will be operating simultaneously. For example,

Hygiene by design

In public washrooms, a suspended toilet pan offers a stylish, contemporary design. However, there are distinct functional advantages for the care sector. A suspended pan offers an additional hygiene benefits, since the overall toilet surface area is reduced and access for cleaning beneath the pan is improved.

Supported on a frame system, a suspended toilet pan is ideal for installation in confined spaces or service ducts. The pipework and all fixings are concealed and, where the mechanism is also recessed, the working parts are inaccessible to users reducing potential vandalism.

User access and comfort is also improved as the adjustable bracket on a frame system ensures that the WC pan can be installed at the correct level for compliance with the Building Regulations4 for wheelchair-accessible toilets (with the pan height 480mm above floor level).

One further hygiene consideration is a rimless WC pan. Designed for maximum hygiene, the bowl is quick and easy to clean, with no inaccessible places where bacteria can take refuge. The adjustable flush volume on the direct flush system is the ideal mechanism to complement a rimless toilet pan, guaranteeing an effective rinse without splashing.

May 2020 •

not behind or into, the wall. The collar also provides support for the wall actuator plate which conceals the whole mechanism and has an integrated electronic unit for sensor models. The Tempoflux 3 is supplied in two kits which simplify installation. A pre- assembled first fix kit means that the housing can be installed and water connections made, system purged and wall finish completed during the first fix. The second kit includes the actual flushing mechanism which is replaced by a temporary casing during

TEMPOFLUX 3 direct flush valve with hydraulic timing

based on a dynamic flow rate of 1.5 litres/second, Delabie estimates that for a block of 20 direct flush toilets, three out of 20 will be activated simultaneously. Another misconception is that direct flush mechanisms are difficult to install and ongoing maintenance is difficult, especially for recessed applications. Delabie has patented an innovative housing that can be installed on IPS panels or solid walls up to 120 millimetres. Unlike conventional housings which are cut flush to the wall, this housing features a collar with an integrated seal which provides a watertight seal against the wall finish. The housing can be cut to size in front of the collar and any leaks or condensation evacuate in front of, and

commissioning. Once the system has been purged and the wall finish completed, the flush valve can be installed during the second fix. The mechanism is fully contained within the housing and can be easily accessed for subsequent servicing. A backflow prevention device is also incorporated within the housing and, in the event of backflow, any water will evacuate in front of the wall.


Direct flush systems offer a hygienic alternative to cistern-flush WCs, reducing the risk of infection in care facilities. Designed for intensive use in public environments, they provide a sustainable solution that manages water consumption, adapting to the usage demands of care facilities, plus they are easy to install and maintain. Breaking the habit of specifying domestic style cisterns will deliver long term dividends in terms of improved hygiene, sustainability and reduced maintenance.


References 1. Aerosol generation by modern flush toilets, Aerosol Science and Technology, 2013 PMC4666014/

2. Water Supply (Water Fittings) Regulations 1999, No. 1148, Schedule 2: WCs, flushing devices and urinals

3. Spotting a leaky loo, Thames Water, 2017. smart/you-can-be-water-smart

4. The Building Regulations 2010, Approved Document M, Vol. 2 (2015 Ed.)

Contact details

Telephone: 01491 824449 Email: Website: LinkedIn: company/delabie/


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