The piano overflow is predominantly a Labyrinth spill, which provides a miniature foundation to build on narrow terrain. The flow through the piano overflow increased from 3 to 5 times compared to the traditional overflow due to the increase in the length of zigzag drainage, especially when the water column was small. Spill has complex structure, ability to remove overflow depends on many shape parameters. The paper presents the results of the study and comes up with a selection of standard sections for piano overflows for optimal removal and economy. The standard piano cross section is determined by the ratio of overflow / overflow widths of 4 to 6 (N = L / W = 4 division 6)
the ratio of the width of the water / key keys is from 1.2 to 1.5 (Wi / Wo = 1.2 divided by 1.5)
the ratio between spill height and single key width P / Wu = 0.5 divided by 1.3
slope of water key into Si = 0.4 divided 0.8.