A draft tube is one important part of a turbine, which is used to transform water into energy. A turbine draft tube is found within the piping system of a turbine. These draft tubes are used in turbines that function in jets, dams, or anywhere else where turbines help do difficult mechanical work.

Turbines need to have a minimum amount of water to propel them in order to produce enough energy. Early versions of turbines, however, did not include draft tubes in their design. Without them, the pressure could drop because of lack of water, and in turn, the entire turbine could fail to work and power could be lost.

The primary purpose of the draft tube within the turbine is to monitor the influx of water. The turbine has something called a "tail race," which is the lowest portion of a dam or construction project where water pools. The draft tube connects the turbine to this tail race, permitting the turbine to be outside of the water but still have access to the water.

A draft tube can be relatively simple to construct. It must, however, be strong and tough enough to withstand the elements and the work of the turbines. Draft tubes can also be either straight or curved, depending on the general construction of the turbine.

With a draft tube, it is possible to maintain the important column of water that keeps the turbine running. The right water level can be maintained despite any potential lack within the amount of material that flows into the machine. In this matter, the tube can help keep the inflow of water into the turbine regular, even if water levels drop, so that the turbine can run properly with the correct amount of pressure maintained.

Often, draft tubes have to be installed underneath a dam, plane, or other machinery that is controlled by the work of the turbine. They must be strong enough to withstand the pressure placed on them. If they are installed or repaired after the turbine is already functioning, sometimes they must be placed while other parts are working as well — sometimes even while air, gas or water is already flowing through the turbine. The draft tubes thus have to be put into place in the turbine through careful movement along the edge of the equipment.