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The exit weir, which controls the flow of water leaving the plant also regulates the water heights in the plant. The weir is a large diameter pvc pipe that functions freefall overflow weir. The equation used to determine the pipe size necessary is a deriviative of the fluid dynamics sharp crested weir equation. The equation was such that the length of the weir, over which water flows is the circumference of the pipe and the equation calculated the diameter of the pipe necessary for that length. The equation used can be found below.

Equation 2 - D.PltWeirEstimated

This calculated diamter is rounded up to next available pipe size.

Inorder to calculated the height of the weir needed the lip height of the water over the edge of the weir has be found. The height of the weir is then found by subtracting the this water lip height from the water level in the exit channel. The height of the water in the exit channel depends on the about of head loss in the sedimentation launders, and thus is calculated at the end of the program.

Sedimentation Tank Exit Launders

Water that leaves the sedimentation tank exits at the top of the tank through holes drilled in pvc pipes that run the length of the tank. The holes drilled in the sides of the pipe create uniform flow of water up through the tank. The water exits into the exit channel. The first step to designing the sedimentation launders is to determine the length of the launders. The launders are defined to run the entire length of the sedimentation tanks, minus the widths of both the inlet and exit channels.

Equation 3 - L.SedLaunder

The size of the launder pipe is dependent on the length of the pipe, the flow through the pipe, an estimated head loss available, and the given acceptable ratio of the flow in the last hole to the flow through the first hole. This function (ND.Manifold) is defined in the fluids functions program and returns the nominal diameter for the mainfold (ND.SedLaunder).

The actual head loss through the manifold is found based on the actual diameter of the launder. The function determining head loss is referenced from the fluids functions program.

This component must maintain some dimensional consistency with the other components of the plant. It consists of having inlet pipes that connect to each sedimentation tank, and a circular weir in the center that will transport the water to the storage tank. It is in the weir where water will be chlorinated.
The height of the leveling tank's wall will be the same as the height, measured from the platform of the plant, as the wall for the channel and the sedimentation tank, which is 70 cm.
The water level in the PLT is the difference between the water level in the channel and the total head loss through the launders:

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