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HOW TO SET SLOPES (FALLS/GRADES)
Working Example 2 (when you do NOT know the grade to set)
Note: If the laser is switched off and on again, this value is lost; as the laser reverts back to auto
level.
Keep the detector clamped in place on the measuring staff & by moving between covers A & B,
keeping a continuous tone on the detector, the ground can be cut away at the base of the staff ,
following the grade set by the laser.
Obviously, allowance must be made for the actual depth of the pipes’ exit & entry positions in
each manhole.
Grade Ratio
As an example, if distance “D” is 20m (20,000mm) & fall “F” is 250mm, the formula shown below
determines the Grade ratio:
Distance “D” in mm / Fall “F” in mm = Grade ratio.
i.e. 20,000/250 = 80
A 1:80 Grade (fall) is used typically for a foul drain run.
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