TundishTundish CS TUND A tundish helps to stop cross contamination between an overflow and a drain pipe. A tundish also serves as an air gap and provides an inspection window to check for water leaks. Without the inspection window on a tundish, you would not be able to see water overflowing from the pressure relief valve. This inwall tundish is easy and economical to set up for air conditioning discharges. Complete with Perspex window, screw on face plate