A buoyant float including a body having an interior defined in part by a side wall and a bottom extending inward from the side wall. The side wall has an upper edge defining an open top of the body. The float includes a cover sized and shaped for covering the top of the body. The cover attaches to the body to maintain the cover in position relative to the body to cover the open top. The cover has a tubular skirt extending downward and around the upper edge of the body side wall when the cover is in position covering the top of the body. An air pocket is created at an interface between the cover and the body when the float is positioned in liquid to isolate the interface from the liquid and prevent liquid from entering the hollow interior of the body through the interface.

In one aspect, a tube device including concentric inner and outer tubes to form an annulus to receive an upright stem in a toilet tank and adjustable vertically and rotationally relative to the stem. In another aspect, an elongated catch device is pivotally mounted intermediately to an inlet tube device and carries at its upper extremity a keeper selectively disposed in the path of a float device to, unless a toilet has been flushed, block lowering of the float device and consequent opening of the control valve.