Flush valves from SCHELL – an FAQ for users

5-minute read

All over the world, people prefer flush valves from SCHELL for their sanitary installations at home or in (semi-)public facilities. After all, flush valves from SCHELL offer all of the features that are important to architects, planners, the skilled trades and end users: a modern design, saving water, excellent reliability, robust materials, support for user hygiene and help for maintaining drinking water quality. With more than 90 years of experience and a range of products unparalleled in the industry, SCHELL is viewed as the global partner of choice for sanitary equipment – including flush valves.

SCHELL flush valves: functionality and benefits

Many end user questions about flush valves from SCHELL focus on the functionality of these systems, whose modern and advanced flushing technology is now an indispensable part of our day-to-day lives. This is why almost all urinals are now flushed with flush valves. WC flush technology from SCHELL is also used all over the world in a wide range of utility systems. And SCHELL flush valves offer key advantages here.

Unlike cisterns, the flush valve supplies the flushing water for direct use without retention – an outlet valve is not required because this functionality is provided by the flush valve cartridge. Compared with cisterns, less installation space is required as well as fewer functional parts.
In this article, we’ve put together a set of useful end-user topics about installation, and special flush valve features for WCs and urinals. SCHELL offers helpful and practical answers to frequently asked questions.

How do you change the flush volume setting on a SCHELL WC flush valve, for example – and how is the output or the flow time regulated?

The flush volume is controlled by the flow time. First, the flow time is set. By controlling the opening duration, this naturally affects the output (litres/min), which is itself influenced by the drinking water system flow pressure and the piping cross-section.
The flow time is adjusted by turning the single slotted-head screw in the head of the SC cartridge on the WC flush valve. This limits the piston stroke in the SC cartridge – turning it in clockwise shortens the flow time.

How does the small flush volume work?

With a fixed stroke length for the piston inside the SC cartridge, a volume of three litres of water is released for a standard drinking water installation and with flow rate regulation opened to 100 percent. A WC flush valve must be pressed for at least one second in order for it to work as intended.

Why is there an opening in the flush valve housing? Water exits this opening – why?

The opening is used as an air intake. Air needs to flow into the valve so that water can flow through the connected flush pipe – otherwise, negative pressure would be created and flushing performance would be unacceptable. If water exits this opening, this means that the water in the flush pipe cannot flow freely as a result of backpressure – created by more than one pipe elbow, for example.

Which type of pipe should I install to supply a WC flush valve?

A DN 20 connection is required as a minimum. For more than one WC flush valve, a correspondingly larger pipe dimension will be needed. We recommend completing a pipe network calculation according to current technical codes.

Water sprays out of my WC without a flush rim when it is flushed. Why does this happen?

Compared with a cistern, WC flush valves create a stream of flushing water that flows differently inside the WC ceramics. Manufacturers of WC ceramics will indicate the suitability of their products for use together with WC flush valves. For this reason, we always recommend checking the suitability of WC ceramics before installation.

Can the isolating valve on urinal flush valves be used to regulate the flush volume?

We always recommend that tapping points are able to be individually shut off for the purposes of inspection and maintenance. The isolating valve on a urinal flush valve can also be used to reduce the flow volume. Step-by-step diagrams are provided in the installation instructions supplied with the SCHELL product.


Whether for public, semi-public or commercial premises, SCHELL offers a wide-ranging product portfolio with advanced flushing technologies. SCHELL also provides end users with a range of practical advice and guidance on its products and solutions. Useful information can be found in our clearly structured installation instructions, for example, and the FAQ on the website. Our brochure (PDF download) also introduces you to the wide range of SCHELL flush valves for sanitary facilities. If you have any questions about flush valves from SCHELL, please get in touch! We look forward to hearing from you via our contact form, a phone call or our chat for industry pros.

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