How It Works
Parameters
To perform the calculation some initial parameters for polos and concrete were set, these are listed below. Beyond this the optimal amount of polo's and concrete above pipe is calculated.
- Manhole Cover = 160mm
- Raising Pieces = 225mm (This is the equivalent to 3 raising pieces 75mm each)
- Concrete Above Pipe = 150mm
- Catchpit Sump = 300mm
Material Data
Pipe Thicknesses have all been collected from the manufactures website data sheet
- Clay = Hepworth
- Concrete Pipes = Marshalls
- Concrete Manhole Rings = Marshalls
- Plastic Pipe = PolyPipe
Material Specifications
Types of Manholes:
Type A:
These are manholes which are more than 3m deep from cover level to soffit. When the pipe size of manhole is 375mm or more a reducer slab needs to be applied. This has been accounted for in the calculations
Type B:
These are manholes which are 3m or less from cover level to soffit. No additional materials required.
Type C:
Shallow manholes where the depth is 1.5m or less from cover level to soffit.
Catchpit:
Traditional Type B manhole but with a 300mm sump below invert of lowest pipe.
Easi Base:
Pre cast base unit which is benched. The unit diameter comes in threee types, 1200mm, 1500mm & 1800mm. The are 5 available depths the unit comes with which are spaced in 50mm increments. This calculator chooses the optimal depth to suit the manhole. Marshalls have been chosen as the Easi Base manufacture for this calculation.