&ldquo;New&rdquo; Adjustable, Sliding Over-flow Tube and Two Inch Flapper Valve Assembly. Sliding Over Flow Tube Slides up and Down to Set the High of Water in the Toilet Tank. By Nuflush NuFlush, sliding over-flow tube and flapper valve assembly Adjust your water height in your toilet tank to any level you need. Replace your flapper valve and adjust your height of water in your toilet water tank. All in one. The easiest toilet over flow tube to adjust on the market. Toilet flapper valves need to be replaced every couple of years.