Abstract: A means to obtain a sample of raw sewage entering a sewage treatment and disposal plant so that the sample is taken during a fixed portion of the time that raw sewage flows into the treatment area of the sewage treatment and disposal plant and is of a constant volume comprised of a vacuum pump with a percentage timer to draw raw sewage through a stand pipe into a sample vessel so that the raw sewage will rise above the top of the stand pipe and then, due to the action of an imperfect flap valve, fall to the level of the top of the stand pipe and remain at this level until the percentage timer deactivates a solenoid valve causing atmospheric pressure to allow a constant volume sample to flow into a sample container.