It is possible for drains that have become defective or are leaking to be lined with a new drain liner. lining drains This method is a fraction of the cost of replacing drains using traditional excavation methods, particularly where drains are located under buildings.
How it is done:
To gain access to the drains, the manholes first have to be located and their lids removed to expose the drainage pipes themselves.
In the event that there are no manholes, the soil will have to be excavated to locate the drain pipes and manholes will then have to be constructed
Firstly, a camera survey is required to determine the condition of the drains and ascertain whether they are suitable for re-lining.
If the drain has collapsed or is badly damaged they will not be suitable for re-lining and will have to be dug up and replaced.
Assuming they are suitable, the drains will need to be jetted with high pressure water to clean the internal surfaces.
The drain liner is a tube of the correct diameter made from a heavy felt type material. This is soaked in resin which has been catalyzed, so that it hardens after a set amount of time. Consequently, it is critical the liner is in place before the resin starts to harden.
Once the liner is in situ, air is forced into the liner under pressure, filling the liner tube and forcing it to open and expand to fit the sides of the existing pipes.
Once the drain liner has hardened, the air can be dispersed from the pipe, leaving the liner in the desired position and ready for use.
Specialist equipment is required to carry out this work.
A Drain liner is suitable for all types of pipes including those made from clay, plastic and even pitch fibre.
Whilst pitch fibre pipes are especially prone to collapsing, on a positive note – it is possible to have partially collapsed pipes reformed as long as they have not collapsed by more than 30% .
Reforming these pipes involves using a correctly sized metal bobbin.
A wire rope, with a bobbin attached to the end, is pushed through the drain run and then winched back through the pipe, reforming the walls as it passes. Once this process is complete, the pipe lining can then be introduced to impede further collapse.
These pipes were introduced as a cheap alternative to the clay version installed from the 1940s to the 1970s. They were manufactured using wood fibre and coal tar- (similar to bitumen.) and were hailed as a ‘ wonder material’ since they were light, easy to handle and cheap.
We have now come to realise they are prone to de-lamination and collapse, with a predicted life span of approximately 40 years.
However, due to their earlier popularity, it is quite possible if your house was constructed during this period, that your drains will be constructed of pitch fibre. If it has become damaged it possible to install a drain liner.
With all drains, it is important that waste can run freely through them to the main sewers. Regular blockages are the best indicator that something is wrong. A camera survey is the best method of establishing faults which, best case, could reveal something as simple as a build up of lime scale or a joint that has moved out of alignment.
Drain camera surveys.
An operator uses a small camera with led lighting. This is fed into the pipe and can be either pushed along or fed in and drawn back. The camera is linked to a video screen and recorder.
The distance travelled is logged, so it easily possible to trace the exact position of a fault once the survey has been completed.