This Part of EN 1555 gives guidance for assessment of conformity to be included in the manufacturer's quality plan as part of the quality system. This Part of EN 1555 includes: a) requirements for materials, components and joints given in the applicable Parts of EN 1555; b) requirements for the manufacturer's quality system; c) definitions and procedures to be applied if third party certification is involved. In conjunction with the other Parts of EN 1555 it is applicable to PE pipes, fittings, and valves, their joints and to joints with components of other materials intended to be used under the following conditions: a) a maximum operating pressure, MOP, up to and including 10 bar 1); b) an operating temperature of 20 °C as reference temperature. For mechanical fittings conforming to ISO 10838-1 [5], ISO 10838-2 [6] or ISO 10838-3 [7], as applicable, guidance for assessment of conformity is not given in this part of EN 1555. When requested, a quality plan based on the tests mentioned in ISO 10838-1 [5], ISO 10838-2 [6] or ISO 10838-3 [7], as applicable, should be set up in agreement between user and manufacturer. EN 1555 covers a range of maximum operating pressures and gives requirements concerning colours and additives. Note 4: it is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account their particular requirements and any relevant national regulations and installation practice or codes.