There are many reasons why a drain may become blocked, with a homeowner themselves the likely culprit of the drain blockage. Homeowners don’t realise the consequences of flushing inappropriate items down the toilet, such as nappies or cotton wool buds, and only realise their mistake when they have to phone a local drainage company.

Besides inappropriate items finding their way into the drainage system, these other things can cause blocked drainage.

• The accumulation of garden debris – Leaf litter and small decorative stones or gravel, which is used on a path or driveway, can find its way into the drainage system through the gullies adjoining your property. This debris can block a drain completely.
• Root growth – Roots can find their way into the drainage system through small fissures in the drainage pipes. When roots find a source of water they can quickly multiply and cause a drain blockage.
• Pipe damage – Drainage pipes don’t last forever and there will come a time that due to age alone the pipes will deteriorate beyond repair.
• Subsidence – Drain subsidence isn’t very common but when it does happen the drain can be damaged beyond ‘no dig’ technology boundaries and excavation may be needed.

Drain blockages in London are an all too common occurrence, as the city’s Victorian sewer system struggles with the pressure put on it by modern life.

When the Victorians built the London sewer network, they were not to envisage the population boom the city has seen over recent decades. And although the system has done well coping so far, there is still far too much sewage dumped into the River Thames at times of heavy rainfall.

Currently only around 2mm of rainfall can trigger a discharge into the River Thames from one of the 57 sewer overflows on the river. When the Thames Tunnel is built it will take the discharge from the 34 most polluting sewer overflows and transfer it to Beckton Sewage Treatment Works where it will be processed.

Thames Water say that on average a discharge is released around 50 times every year and a total of 39 million tonnes of sewage is released into the river. If the proposed tunnel build does not go ahead the forecast for annual sewage release is expected to increase to around 70 million tonnes, which could have a huge impact on the river and its wildlife.

If you have a recurrent drainage problem, you might need a drainage company to look into the problem in finer detail. Jetting does remove drain blockages, but if the blockages are frequent there may be some reason why this is happening.

There are many reasons why a drain can become blocked, but there is usually a trigger which causes a blockage. It may be that there is a part of the drain which has a rough surface, a drain may be cracked or deviated, a drain may even have roots growing in it. The only way a drainage company will find all these things is if they conduct a CCTV survey of the drain so they can visually interpolate the internal workings of the drainage system.

Roots are one of the most frequent reasons for recurrent drain blockages. These roots find their way into the drainage system, and when they find an easy supply of water they quickly multiply and block a section of the pipe.

To remove roots from a drain, a drainage company don’t usually have to excavate. They simply have to use a spinning root cutter which they insert into the drain. This cuts the roots back to the internal dimensions of the pipe. When this is done the drainage company will insert a liner into the pipe which stops the roots growing back.

If you are having recurrent drainage problems, your local drainage company in London might suggest that you have a CCTV survey to see if there is any structural damage to the pipe network.

CCTV surveys are an important tool and can be used to assess damage within a section of pipe. When a drainage company knows what is wrong, they can suggest a suitable repair.

If during a CCTV survey a section of pipe is found to be cracked or if there is a gap between sections of pipe, the drainage company may suggest a liner repair. To install an epoxy flexi line, the drainage company simply has to blow the liner into position to the corresponding section of damaged pipe. Once the liner is in position the drainage company inflate it and the impregnated resin liner sets, bonding it to the pipe wall. This covers any fractures in the pipe and stops water getting through the pipe and causing a damaging void.

When the liner is in place, the cross section of the pipe will be slightly reduced but the pipe will be repaired so the flow rate will be increased by as much as 15%.

Drainage pipes can become damaged or misaligned after years of use. This can be quite common and can usually be put down to age or ground movement. When this happens a drainage company has one of two options. Either they can excavate a section of the pipe to instigate a repair or they can insert a pipe liner into the pipe so the cracks or other damage are covered.

Drain lining technology has improved drastically over the last few years and now even pipe runs of up to 80 metres can be lined quite successfully with no loss of waste carrying capacity. For large diameter pipes run lengths will be reduced, but pipe integrity will still be restored.

To reline straight sections of pipe the best technology to use is a polyester resin felt liner, whereas if the pipe deviates in any way epoxy flexi line is the preferred method. When the liner is inserted into the pipe into the correct position, air is used to inflate the liner to the same internal diameter as the pipe. Because the liner is impregnated with resin, when it cures, it provides an effective seal against any liquid escaping from the repaired section of pipe.