Type testing is done on polyethylene according to EN 12201 for water pipes and EN 1555 for gas pipes.
Initial type testing is performed by the compound manufacturer and include among other MRS classification of the material.
EN 12201/EN 1555 also regulate the reoccurring testing for compound manufacturer and piping system producer. There is also guidance what to test if anything is changed in the production or formulation of the compound, aka process verification testing (PVT).
We can offer the complete package and guidance how to get your compound certified.