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Exam revision materials for Plumbing Level 2&3 and ACS Gas Safety test

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Sanitary Pipework Systems

Waste Systems

Ventilated Discharge Brunch System

  • Main Ventilating Stack joins the main ventilating stack above the spill over level for the appliances
  • Each appliance has its waste vented
  • Brunch Ventilating Pipe:
    • MIN 25mm if < than 15m
    • 32mm if > 15m or > 5 bends or serves > 1 appliance
    • 750mm MAX from the trap to the vent pipe 
    • ifindplumbers
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Stub Stack System

  • preferred where the numbers of sanitary appliances and their distance to a discharge stack are large
  • NO WC connected above 1.3m from the invert of the drain
    • On the stub stuck system the MAX height above the invert to the centre of WC bunch is 1.5m
  • MAX 2m from the invert to the highest brunch connection
  • Stub Waste connection – direct waste pipe connection to the drainage system
  • The top of the Stub Stack SHOULD be finished with End Cup (Screwed Access Plug) or Air Admittance Valve (CAN terminate inside a building)
  • Stub stacks may also be used on upper floors where the discharge from the stack is to a ventilated soil stack.
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Primary Vented Stack System

  • previously known as the single stack system
  • Installed in most new buildings and domestic premises
  • NO separate ventilation pipe required
    • The discharge stack and branch pipes are sized to avoid the need for separate ventilating pipes
  • There are limits on length, diameters, gradients and branch waste pipes
    •  this system saves space and costs 
    • The distances of sanitary fittings can be exceeded if using resealing (or antisiphon) traps and branch pipe air admittance valves
  • Appliances SHOULD be grouped closely together
  • BS EN 12056-2 allows external pipework on buildings up to three storeys
  • To minimise noise transmission it's recommended 25 mm of insulation around soil pipes passing through a bedroom or living room.
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Secondary Ventilated Stack System

  • The venting stack is usually half diameter of the discharge stuck
  • Appliances SHOULD be grouped closely together
  • Separate ventilating overcomes pressure fluctuations that could cause trap seals to be lost
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