What it involves

A ‘hat’ shaped liner that seals the connection between a lateral drain or sewer and the pipe it connects to.

Our Service 

  • The Epros LCR System Drain is our most frequently used solution followed closely by the Hächler EL300/600 Grout injection lateral repair unit
  • The Epros system installs a polyester resin impregnated corrosion resistant fibreglass insert
  • It forms a leak-tight bond with the lateral to the main pipe
  • The delivery unit is an LCR packer that carries the resin-wetted hat profile and pushes it into position with an “extensible finger” once in position.






Our Process

  • An LCR packer carrying a wrapped-around resin-wetted hat profile is driven to the point of repair
  • The exact position of the damage is determined beforehand by TV inspection
  • The resin-wetted hat profile is extended and inverted out of the packer body by the extensible finger connected to the control system by calibration hose
  • Monitored by the on board CCTV camera and if appropriate a separate downstream camera, the finger goes up the lateral junction until forced against the host pipe of the junction in a tight fit
  • Excessive reaction resin migrates into the defective regions. This creates a permanent bond between the fibreglass of the hat profile, the host pipe and the lateral connection, when the resin cures at ambient temperature. The time is determined by the designed resin mix and proven by a surface sample.
  • After the complete cure of the reaction resin, the packer is deflated, the finger retracted and the packer removed from the pipe
  • Finally, the repaired pipe section is inspected and documented with by CCTV survey


  • Pre-survey and accurate measurement of the host pipe and lateral connection(s
  • Safe access and working area around chambers to be used.
  • Knowledge of probable flow rates and over- pumping / temporary sealing as appropriate.


When to use top hats for lateral connections

  • To be used when there is a significant risk of exfiltration through defective connections causing ground water pollution or conversely when the effect of ground water infiltration washing soil into the sewer system causes voids to be formed around the joints. The other problem with infiltration is the unnecessary treatment and management of high volumes of ground water in downstream treatment works
  • It is often the case that damage to the sewer system is first evident on the joints between the main sewer line and the laterals. Cracks appear on the joints due to slight movements in the pipes relative to each other, which are caused by poor installation, temperature fluctuations or heavy traffic. Top hats enable the accurate repair of the problem without expensive excavation and difficult external repair attempts

Why choose the McAllister Group for lateral connection repair by ‘Top Hats’

People – We have two dedicated top hat teams and a large number of staff with the relevant manufacturer training and experience as support operatives.

Experience – As an early-adopter of this system in the UK, the McAllister Group is now the leading installer of top hats. Supporting the position is a robust installation and quality management system which focuses our attention on getting it right first time. The 400 plus installations we complete annually bears testament to this

Partners – EPROS provide all the relevant technical support and training to our teams. Our other partners do likewise providing technical and installation support for our less frequently used systems.