Can different grades of PE be connected to each other?
It is possible to butt fuse pipes and fittings of different grades and SDR, but this should only be carried out under controlled conditions. In case of doubt please contact the pipe and or fitting suppliers.
Similarly different grades and SDR's of pipe can be connected using electrofusion, again only under controlled conditions. Special care needs to be taken to avoid collapse of thinner pipes during the fusion period.
Electrofusion fittings may also be of different grade and SDR than the pipes, in which case the lower rating (pipe or fitting) governs the rating of the assembly as a whole.
Mechanical jointing may be used to connect different grades and SDR's, with the same limitations as above for the electrofusion method. Special care should be take to use the appropriate insert stiffeners to the corresponding SDR.
Note: the use of different grades and SDR's could reduce the maximum operating pressure of a network.
IS0/TR11647:1996 Fusion compatibility of polyethylene (PE) pipes and fittings