PVC Compression Fittings can be used to join various pipe materials. Suits either iron, plastic or steel pipe sizes and can attach plastic pipe to threaded valves or fittings. Available this season is a new 150mm size fitting! Watermark Certificate of Conformity As of 2nd February 2011 HOLMAN Industries are proud to be Watermark Certified ? Level 1 ? Evaluated to AS/NZS 1477 PVC Pipes and fittings for pressure applications ? 2006.