Fabricated PE Fittings
In general, heat fused PE pipe and fittings do not require thrust blocks to restrain the longitudinal loads resulting from pipe pressurization or possible temperature changes. However, the attachment of valves or other appurtenances used with PE pipe systems can cause excessive loads, which may be prevented by proper backfill in most situations. Common fittings, elbows and equal tees normally require the same backfill as specified for the pipe. The use of concrete support pads, thrust blocks on hydrants, self restrained PE mechanical joint (MJ) adapters and sand stabilized with cement around the reducing tee are recommended practices. Compaction of the soil around these fittings is difficult and the use of sand stabilized with cement or flowable fill is a convenient alternative.
Typical Assembly and Support Arrangement for PE Pipe Connections to Valves and Hydrants
Additional details are provided in Chapter 7 of the Plastic Pipe Institute (PPI) Handbook of Polyethylene Pipe, which is available at www.plasticpipe.org/pdf/chapter07.pdf.