Abstract: An overflow arrangement which includes an upstanding fluid retaining wall spaced radially outwardly from and encircling an upstanding externally threaded fillneck on a surge tank or overflow reservoir so as to define an annular channel therebetween. A cap adapted to be screwed onto and off of the upstanding threaded fillneck is provided, the cap having a generally circular-shaped top wall, a skirt depending downwardly from a radially outer periphery of the top wall and a radially outwardly extending flange contiguous with a lower extremity of the skirt to a radial extremity overlying an upwardly facing extremity of the upstanding fluid retaining wall.