Toilets are an obvious source of harmful germs. Cisterns store water in ideal conditions for bacterial development and these bacteria are released in an aerosol plume during flushing, but they can also spread back through the pipes and colonise the system.
The alternative to cistern-flush mechanisms is a direct flush system which connects directly to the water supply. A self-closing valve discharges a pre-determined flush volume without the need for stored water. By employing system pressure to rinse the pan, there is no water stagnation, scale deposition or build-up of impurities upstream of the flush mechanism.
Direct flush improves hygiene
Water Supply Regulations (1999) require the pan content to be “cleared effectively by a single flush of water”. Gravity-fed cistern-flush mechanisms may not have sufficient dynamic pressure to ensure a hygienic rinse with a single flush, and a 40 to 60-second refill time exacerbates the problem. Replacing the cistern with direct flush valves has several hygienic advantages. Firstly, the flush volume can be adjusted to the dynamic pressure to ensure an effective single rinse. Where necessary the flush can be adjusted for ecological or smaller children’s WC pans. This reduces the aerosol flush plume, prevents unhygienic splashing and avoids the risk of slipping on wet floors. In addition, since there is no refill time, the full flush is instantly available for subsequent users, delivering an effective flush every time.
Hygiene can be further improved by installing an electronic flush mechanism. For example, DELABIE’s TEMPOMATIC Dual Control direct flush valve (Image #2) has a user-activated conventional push-button flush. However, an automatic sensor also detects their presence and flushes the valve automatically if the user forgets. An intelligent rinsing system identifies the duration of use and flushes accordingly. There are 3 programme options, including an ecological setting with a reduced flush length equating to a lower flush volume.
Electronic flush systems have the additional benefit that no manual contact is required, so the toilet is accessible to any user, regardless of age or level of independence. Furthermore, an automatic duty flush can be programmed to flush the pipework every 12 or 24 hours when not in use, preventing stagnation and reducing biofilm development.
Fit for purpose
Cistern-flush toilets are usually installed through habit but, although they are ideal for domestic usage patterns, the mechanism comprises plastic components that cannot cope with the regular and intensive use experienced in public buildings. Heavy-handed users can easily break fragile mechanisms. Depending on water quality, watertight seals which are sensitive to scale and impurities quickly wear out with repetitive use. This inevitably leads to leaks and reduced flushing capability.
According to Thames Water, a leaking toilet can waste up to 400 litres of water a day, and a leak in a cistern-flush toilet is very difficult to detect. The resulting maintenance is time consuming and problematic, especially where cisterns are installed on frame systems behind IPS panels. However, with direct flush systems, 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 3 (Image #3) relies on water pressure to operate, so there is no metal–metal or metal–plastic friction. A self-cleaning timing groove reduces maintenance and extends the operational lifespan to over 500,000 activations. Furthermore, the cartridge is standardised and can be exchanged 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 activates for 7 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, based on a dynamic flow rate of 1.5 litres/second, DELABIE estimate that for a block of 20 direct flush toilets, 3 out of 20 will be activated simultaneously.
Easy to install
Another major concern is the ease and convenience of installation and ongoing maintenance for direct flush systems, especially in recessed applications. DELABIE has patented an innovative housing that can be installed on IPS panels (Image #4) or solid walls up to 120mm (image #5). 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 (image #6). The housing is cut to size in front of the collar and any leaks or condensation evacuate in front of, and 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 flush valve is supplied in two kits, the hydraulic connection is made from the exterior with temporary caps to replace the sensitive elements while the system is purged. The mechanism and electronic unit are then connected inside the housing, but 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 commercial washrooms. Designed for intensive use in public environments, they provide a sustainable solution that manages water consumption and adapts to the usage demands of public 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.