What is a Sovent fitting?

A Sovent fitting is a special branch fitting in the discharge stack of a multi-storey building, to which the branch discharge pipe of each floor is connected. A partition inside the fitting guides the stack flow around the connection point. Water falling down the stack and water coming in from the floor therefore do not collide head-on, an air core is kept in the stack, and the flow velocity is reduced. The system was developed in 1959 by the Swiss Fritz Sommer and is best known today as Geberit HDPE Sovent. It is a form of single stack drainage; in Dutch the fitting is simply called a sovent.

Why use it?

In a conventional stack, water entering from one floor can briefly block the pipe. The resulting pressure fluctuations can siphon traps dry, which is why conventional high-rise systems use a parallel (secondary) ventilation pipe. With Sovent fittings that extra pipe can be omitted in many cases, and the stack can be smaller. Geberit states a maximum flow rate of 12 l/s for stacks with Sovent d110 fittings and 17 l/s for d160.

Application

Key points for design and installation:

1. Use it in high-rise buildings. The manufacturer specifies buildings with more than 5 floors as the application range.
2. One fitting per floor. Install a Sovent fitting on every connected floor, where a standard branch would otherwise go.
3. Vent through the roof. Each Sovent stack must be individually ventilated through the roof without reducing the pipe size.
4. Follow the rules for the base and offsets. The transition into the horizontal collector pipe and any stack offset have their own manufacturer design rules; otherwise EN 12056-2 applies.
5. Jointing. The closed spigots are cut off, then pipes are connected by butt fusion, electrofusion coupling or a push-fit socket.

Common mistake: detailing the base of the stack as for an ordinary stack. The pressure advantage is lost and traps can still be siphoned.

Related terms

• Waste water
• Sewer
• Drain trap
• Soil vent pipe
• Air admittance valve
• Welding

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