RIGID pipe producers have accused plastic pipe manufacturers of misleading contractors and pipeline installers over the capabilities of plastic sewer systems.
They claimed that a briefing note sent out to installers by the British Plastics Federation had misled contractors by suggesting that plastic pipes have a number of advantages over rigid clay and precast concrete sewer systems.
The note, seen by Construction News , claimed improved performance for plastic and structured wall over rigid systems because the inner bore is smoother.
It said: 'Plastic sewer systems offer specific benefits over rigid (clay and concrete) systems, including benefits in performance such as less likelihood of blockages due to the smooth, non-porous bore.'
But Edward Naylor, chief executive of concrete and clay pipe producer Naylor Industries, said the claims were misleading.
He said: 'It makes it sound as if plastic pipes are better than concrete and clay because the inside bore is initially smoother. But all sewer pipes are subject to sliming and have the same smoothness of bore after a short period of use.There is no advantage for plastic.'
The briefing note was sent out to installers following the move by utilities group United Utilities to back down on its decision to charge developers for surveys on plastic sewer pipes offered up for adoption.
It announced it will now bear the cost of initial light line surveys on plastic sewer systems following lobbying by the British Plastics Federation.
Light line surveys are used to check the deformation of plastic and structured wall pipes after installation by superimposing the outline of the as-installed pipe over its ideal cross section. Operators can then determine how much the pipe has been squashed by soil reinstatement following installation.
The UK limit for deformation is set at 6 per cent of the inside diameter of the pipe, but United Utilities has toughened up this target to 5 per cent or less before it will consider adoption of the installation.
The BPF guidance note claimed the ability of a structured wall plastic pipe to deform under loading was actually a benefit, but one clay pipe producer dismissed the idea.
He said: 'To claim that deformation is an advantage is absurd.There is an accepted world-wide view that in excess of 6 per cent deflection increases the risk of joint failure and buckling to an unacceptable level.'
But plastic manufacturers claimed loading on rigid pipe systems would smash the pipes, causing them to fracture and collapse.