Automatic Siphons

DESCRIPTION:

Automatic siphons allow urinals to be flushed with a pre-determined quantity of water at regular intervals. They are simple and reliable devices which contain no moving parts.

The operating principle of the valve is similar to an inverted unequal U tube, the longer leg of which is connected to the flush pipe; the other shorter end sits a little above the bottom of the cistern. As the level of the water within the cistern rises it also fills the inside of the short leg. When the level reaches the top of the U it begins to fall down the longer leg and out into the flush pipe. Because the cistern is full of water and the end of the short leg lies beneath the surface, no air can enter the siphon.

The weight of water in the flush pipe leg, being greater than the weight of water in the short leg begins to suck out the water from the cistern. This suction continues until the water level in the cistern falls low enough to expose the short end of the U tube, at which point air enters and breaks the siphon.

The quantity of water discharged during each flush is determined by 2 factors; the area of the cistern in plan view (i.e. looking down onto the top of the cistern) and the height of the automatic siphon. The interval between flushes is regulated by controlling the flow of water into the cistern via a Petcock.