In sewerage and drainage, it is not the horizontal plane that matters, but the slope . Too small and the water stagnates, dirt settles. Too large and the water drains away faster than the solid parts. A rotating laser will help maintain the slope along the entire length of the pipe.
What does slope mean in percentage?
The percentage slope tells you how many centimeters the pipe will fall for every meter of length:
| Slope | Drop to 1 m | Drop to 10 m |
|---|---|---|
| 1% | 10mm | 100mm |
| 2% | 20 mm | 200mm |
| 3% | 30 mm | 300mm |
The slope to choose is determined by the project and the relevant standards according to the pipe diameter and type of wastewater. For house connections, in practice it is most often around 1 to 3%, but always take the exact value from the project documentation.
Method 1: classic laser and conversion to lath
With a conventional rotating laser that holds a horizontal plane, the slope can be calculated by:
- Place the laser on a tripod and let it level.
- At the beginning of the pipe, place the batten on the bottom of the trench and set the receiver – for example, read 1,600 mm.
- At a 2% slope, the bottom of the trench must be 200 mm lower 10 m further, so you read 1,800 mm on the staff.
- Move the receiver to 1800 mm and adjust the bottom of the groove until the receiver beeps continuously.
It works reliably, but on longer routes you have to continuously recalculate waypoints.
Method 2: Laser in slope mode
A classic laser can also be tilted manually within a range of ± 5°. The laser plane is then inclined and the receiver on the staff simply copies the desired slope – the height of the receiver does not need to be changed. However, setting the exact slope manually requires some experience.
Method 3: digital slope laser
The digital rotary laser has a display where you enter the slope in percentages separately for the X and Y axes , for example X = 2.00%, Y = 0.00%. The laser levels itself and maintains the inclined plane. You only need to set the receiver on the staff once at the beginning and check the entire length of the line – whether it beeps continuously.
What makes a digital laser the most worthwhile:
- sewer and rain connections,
- drainage around the house,
- paved areas, parking lots and yards where water must drain into drains,
- garage entrances and ramps.
What to watch out for
- Point the laser axis along the pipe. The X and Y axes are marked on the laser – the axis with the slope must point in the direction of the route.
- Check the bottom of the trench and the top of the pipe. The sand bed may settle during compaction.
- On long routes , check the gradient every few meters, not just at the beginning and end.
If you are considering whether a digital laser is worth it or want advice on setting the slope, give us a call.