Cast Iron P-Trap Adapter

Transition for adapting Cast Iron P-Trap spigot to PE pipe

Where existing Cast Iron P-Traps are connected to PE pipe, a Rubber Ring joint (RRJ) Transition adapter is required to make a leak tight connection. The transition adapter will be either Eccentric or Concentric in design, depending on the PE pipe size connecting to the P-Trap. Eccentric connectors ensure the level invert is maintained and no septic pooling of wastewater or blockage step exists at the joint between the PE and cast iron.

Recommendations for anchoring the RRJ transition socket to the P-Trap / Chamber wall are given below, two possible conditions are considered:

Option 1: Normal Condition - Where there are no significant ground or thermal forces forces acting on the pipe.  The pipe is buried and installation is not in reclaimed land or on a significant slope.

Option 2: Special Condition - Where ground movement is expected, such as installation in reclaimed land, installation on a steep slope, installed above ground or where the pipe is subject to significant thermal forces.


Existing P-Traps may have non standard dimensions. We recommend confirming the Cast Iron P-Traps spigot OD before ordering the transition, to ensure the transition will fit and seal correctly when installed. installation procedure and submission documents can be downloaded below:

Submission Document Option 1 – Standard Install

Option 1 Installation 

Submission Document Option 2 – Special Condition Install

Option 2 Installation


PE to Cast Iron Transition (P-Trap) / Spigot / Socket / SDR 17

PE100 Single piece transition adapters, machined from Hollow bar with integrated puddle flange and supplied with a BS EN 681-1 NBR (or equivalent) rubber sealing ring. Sockets can be machined to order once the actual Cast Iron spigot diameter is known.

The design of the transition is Eccentric if the ID of the PE pipe (SDR17) and the ID of the CI fitting is greater than 5% difference.  Eccentric design avoids an internal step.

non-Waterstop with Waterstop DI Pipe
Pipe OD
dn (DN)
Fitting rating
Type Long Spigot Length
LS Length
Availability in Hong Kong
P531E.055.160160 P531E.955.160160 150 CI EN877 160 17 Eccentric 150 384 4-6 weeks
P531E.045.225222 P531E.945.225222 200 DI EN598 225 17 Eccentric 150 395 Ex-Stock
P531E.050.250247 P531E.950.250247 225 CI 250 17 Concentric 250 473 Ex-Stock
P531E.055.280274 P531E.955.280274 250 CI EN877 280 17 Eccentric 250 508 4-6 weeks
P531E.050.355326 P531E.950.355326 300 CI EN877 355 17 Concentric 300 521 4-6 weeks
P531E.043.400378 P531E.943.400378 350 DI EN598 400 17 Concentric 300 568 4-6 weeks
P531E.055.400403 P531E.955.400403 375 CI 400 17 Eccentric 300 624 4-6 weeks
P531E.055.450429 P531E.955.450429 400 CI EN877 450 17 Eccentric 300 614 4-6 weeks
P531E.045.500480 P531E.945.500480 450 DI EN598 500 17 Eccentric 350 721 4-6 weeks
P531E.050.710635 P531E.950.710635 600 CI EN877 710 17 Concentric 350 667 4-6 weeks

Note: CI P-Traps vary from manufacturer to manufacturer. The OD of the cast iron spigot must be confirmed before ordering.