Thomas Dudley Tri-Well Black Well Bottom Cistern Part No. 313510. This high-level flush cistern is perfect for use in public restrooms that may be subjected to vandalism or misuse. Features Tri-Well plastic cistern tanks providing ready-made replacements for most rubber and cast iron well bottom cisterns. Includes side inlets, plastic outlets, and nuts with internal or external overflow warnings. Internal parts comply with the regulator's specification. WRAS approved Dudley Turbo S1-11 2 part syphon as standard, which can be serviced in under 5 minutes without disconnecting the water supply and dismantling the cistern chain pull. Suitable for high-level installations. The chain pull can be fitted on the left or right side.