How to set Slopes (Falls/Grades) with a Rotary Laser Level
The following description in this guide, explains the general principles of setting a
Slope (Fall/Grade) when using a rotary laser level. The rotary level must be either a
“grade facility” laser with a Manual over-ride button or a true grade laser with a LCD
enabling the User to input slopes into the X-axis, Y-axis or both together ie. Dual
Grading.
This information is intended to be read in conjunction with your laser level’s
Instruction Manual.
Equipment:
You need a rotary laser level, a surveying tripod, measuring staff (rod) with mm scale
and a laser detector/receiver. Its not essential but having a remote control for the laser
level is preferable. (Without a remote control, having another person to assist you, is
essential).
Site Conditions:
There are many different worksite scenarios. As an example, we are assuming that
you are outside on a site with a clear field of view and planning to set drainage falls.
All above ground and below ground drainage pipes should be laid to an adequate
gradient. The fall in a pipe is defined as the vertical height by which the pipe drops
over a known distance. eg. a 2.5% gradient is a fall of 1m over 40m or 1:40. (1 in 40).
Typically, surface water or foul water drainage pipes are set at 1:40 to 1:80.
If a gradient is too steep ie. steeper than 1 in 40, the liquid may run faster than the
solids in a foul water pipe thus leaving the solids stranded, which could then block the
pipe. Conversely, if a gradient is not steep enough (usually less than 1 in 110), then
the pipe may still block, if the solids slow down and become stranded.
Procedure:
Place the rotary laser horizontally on the surveying tripod, switch it ON and allow it
to auto (self) level. Note the X-axis / Y-axis markings on the top cover of the laser.
Setting a 1:40 gradient:
Position the measuring staff say 10m away from the tripod,
held vertically and move the laser detector (receiver) along the staff to find the set
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