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Richard Bailie Tech Talk: lack of ducts in residential class buildings (Part 2)

    • SANS 10252-2: Water supply and drainage for buildings Part 2: Drainage installations for buildings
    • SANS 10400-P: The application of the National Building Regulations Part P: Drainage
    • For plumbers to be able to comply with the installation standards of drainage, therefore in at least a one-pipe system it requires good access to the pipes in terms of SANS 10252.

This is part 2 of a three-part article which have to be read together for the full presentation.

The standards also say: “Any part of the pipe may be built into brickwork or concrete provided that the interior of the part is rendered readily accessible for cleaning and maintenance.” I don’t interpret that as being an allowance to build a stack into a wall. The discharge pipe or stack must be accessible for maintenance, and if the discharge pipe is intended to be enclosed within a building, it must be enclosed within a duct. What it’s saying here is that if you need to pass pipes through a concrete floor or a brick wall, ‘passing through’ is different to being ‘totally enclosed’.

SANS says: “When you pass through a wall or whatever, make sure that there is a means for you to get inside that pipe from a rodding eye – an access point at some location without you having to chop and break a wall to get to that”. It also mentions its vicinity to other services, in particular hot water pipes.

Hot water pipes have an ambient heat which radiates out. Waste pipes suffer a thing called dry out and what happens when a waste a discharge pipe or a stack dries out is the incidence of biofilm. This is something which exists in waste and sewage pipes: it is a film of matter which sits on the inside of waste or discharge. There can be a large build up of it. If it’s an unhealthy system, that biofilm can start causing problems. In drier climates it becomes hard and forms an obstruction.

Then the pipe becomes prone to blockages, which is not a favourable condition to have within a waste or sewage pipe. That’s why waste pipes should not be installed within at least 75mm of hot water pipes because of the temperature. If the pipes aren’t insulated it should be 150mm.

For plumbers to be able to comply with the installation standards of drainage, therefore in at least a one-pipe system it requires good access to the pipes in terms of SANS 10252.

Examples of this are connection restrictions within a single stack one-pipe system. A one pipe system means that a single stack or a single pipe is used as the discharge stack as well as the ventilation stack. A two-pipe system will have a dedicated ventilation stack and a dedicated discharge stack. Most systems are one pipe systems and they are subject to connection restrictions. There are areas within a stack within which you may not make connections for the reason that as water changes direction around a vent, for example, the flow of the water changes and the shape of the water within that pipe changes and there may well be areas within that area where the pipe is completely filled with water. When the water is no longer able to flow past and if you have a connection there, it plays havoc with the connection.

At the horizontal part of the stack (the bottom) it becomes a drain at that point and at the bottom part of the horizontal part of the drain within 2.5 meters of the foot of that you may not make a connection. If these regulations are to be followed, the plumber needs correct access to the drains, and consequently ducts are necessary.

Written by Eamonn Ryan based on an IOPSA Tech Talk by Richard Bailie on lack of ducts in residential class buildings

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