How CCTV drain inspections work

The line usually has to be cleared first

A pipe full of standing water and debris shows you almost nothing. In most cases the drain is jetted first and then inspected, which is also the order that tells you the most: you see the pipe in its normal state rather than buried under the blockage.

The exception is where the history points to a collapse. If a line has failed structurally, we would rather look before putting a jetter down it.

What we are reading

• Pipe material and joint type, which tells you what failures to expect
• Root intrusion, and how much of the bore it has taken
• Cracks and fractures, common in older earthenware under driveways
• Displaced or open joints from ground movement
• Sags and back-falls, sections that hold water instead of draining
• Collapsed sections where the pipe has failed and ground is entering
• Foreign objects, and in newer houses, leftover construction debris

Marking the spot

The camera head carries a sonde, a small transmitter. A receiver walked over the ground above picks up the signal and peaks directly over the head.

That gives a position and a depth, marked at the surface. It is the difference between digging one targeted hole and trenching across a yard hoping to find the fault.

What a camera cannot do

It shows the inside of a pipe. It does not show what the ground around the pipe is doing, and it cannot measure remaining wall thickness or predict how many years a line has left.

It also cannot see through a solid blockage or standing water, which is why clearing generally comes first.

Be wary of anyone quoting a repair without having put a camera through and shown you the footage. If they cannot show you the defect, ask why.