When Drain Lining Goes Wrong
When done correctly using the right materials and technique drain lining can save major disruption and upheaval whilst delivering a permanent and quality repair, when liners are poorly installed they can cause untold problems and usually in areas not related to the initial problem, an excavation can often be the only way of removing the defective liner.
Liners can and do go wrong occasionally and it has happened to the best of us, it is usually down to human error, inexperience or a ground water issue that you were not aware of but in truth it has never been easier to install a cipp liner system. Modern materials and resins are reliable and can be ordered in pre-measured and mixed quantities taking all the risk out of the calculation and mixing process.
 Typical defects on liners are due to;
- Poorly wetted out liner leaving a rough or course finish to the liner wall
- Resin washed out of liner end due to poor wetting out or water flow prior to inversion
- Poor preparation of system prior to installation including roots, debris, encrustation not fully removed
- Debris drawn into the system during the installation of drag in liners
- Liner over stretched or twisted during installation
- Excess resin left in system after installation causing blockages
- End of liner not fully opened when inversion hose inflated, usually on single entry liners
- Lip or step caused by liner in outlet of a manhole or inspection chamber
- Wrong type of liner used causing wrinkles on bends or changes of direction
The worst liners we come across are simply down to poor workmanship and the guys are either trying to do too much in one day or they are on job and finish so anything goes, there is a certain element in the industry who move from one company to another on a regular basis so they have little regard for the long term result of a poorly installed liner. We then have the contractors who will reline anything in order to raise an invoice even though there comes a point on any system where defects such as stepped joints or a severely dipped line are beyond a Cipp liner repair.
The image above right shows a poorly installed liner end on the outlet of a manhole, the jagged edges at the base of the liner caused a build up of paper and waste until the system eventually blocked.
Removing Defective Drain Liners
There are a few techniques for removing defective liners but in most cases due to the time and effort required the shovels are usually out of the van and a big dig ensues, however there are occasions when digging is not an option so you could try the following.
- Cutting/Grinding - If its the end of the liner that has not opened or there are a couple of rogue wrinkles or some debris trapped under the liner then a robotic cutter can be used to grind out the defect before using a patch liner repair to make good.
- Winching/Splitting - this is where you winch a splitting head through the liner shredding it as you go, probably better suited to drag in liners as apposed to anything that has adhered to the host pipe or its joints.
- Steam Jetting - there was a contractor who would use steam to soften the liners before winching them out, never seen it done but i read an article on it some years back.
- Pipe Bursting - Tried and tested method where if you can get a line through you can drag a new pipe though the liner splitting it as you go, no good if there are any lateral connections and you will need an excavation at each and of the defective liner.
- Install Parallel System - if all else fails and the liner can not be removed you can try to install a parallel line, this usually involves an impact mole and pipe bursting rig or a directional drilling rig. Not cheap and specialist work but if a full excavation is not an option worth considering.
- Cleaning Up Liner End - Its a relatively easy job to tidy up the outgoing liner from an inspection chamber using a grinder before inserting a patch liner repair for a smoother transition from the host pipe to the relined pipe work.
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