Back to Inclination Measurements

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Background

Under ‘normal’ conditions, drains flow by gravity and run downhill in the direction of flow, so the upstream end of a drain is usually at a higher altitude than the downstream end.

The only times that this does not happen are:

• If the pipe is a pumping (or force or rising) main so it has a pump at the upstream end and the downstream end of the pipe is higher than the upstream. It would very unusual to measure the inclination of this type of pipe.

• The pipe has failed or been badly installed so that the downstream end is higher than the upstream end.

The Equipment

Inclination measured by an inclinometer which is a device usually inside a CCTV crawler similar to an accelerometer that can measure very small changes in attitude, which can then be processed into a curve that represents the shape of a pipe in the vertical plane between;

• one specified point and one calculated point, or

• two specified points.

While an inclination test is being carried out, the camera will be sometimes looking up and sometimes looking down and sometimes level during the test so we will be recording a mixture of positive and negative values along the length of the test.

Open

When completing an inclination test it is best to keep the camera moving at an even speed and not to stop or reverse at any point. With this in mind and when considering the options described in Test Options, if possible it is best to do the CCTV inspection while driving forwards along the pipe and then the inclination test while returning the camera back to the TV truck. Working in this way means that almost no additional time is needed on site to make a sewer inspection with or without an inclination test.