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standpipe elevations

I am working on a water distribution system where the village has one existing standpipe.  The water supply to the village is provided by a nearby city through its transmission main water supply system, and delivered into the village at a single connection point. The static pressure at this point of delivery is 90 PSI. The pressure is then  reduced to 60 psi before delivery into the village. In the model I set up a tank to represent the connection point and reduced the tank initial elevation to 780 to allow for 60 psi in that first junction into the system (ground elevation at the first junction =645).  I also have a standpipe in the village as well, however I am not entirely sure what to set the WaterCAD tank elevations for the standpipe?

  • First, you need to understand that WaterCAD gives you two ways to specify tank elevation - elevation and level.

    Elevations are given relative to your datum (usually mean sea level) while levels are given relative to base elevation (usually the ground at the tank).

    So if your standpipe is at 600 ft and is 120 ft tall and water level is 700 ft. 

           Elevation    Level

    Base El   600            600

    Initial       700            100

    Maximum 720           120

    Is this an existing tank or one you are designing?

  • This is an existing stand pipe and I have the elevations.  Base = 699, overflow = 783, HWL=781, LWL= 779. I don't understand what to set my operating or initial water level to. If I set it between 781 and 779 there be a large amount of water that is not used as effective volume? The ground elevations vary from 588 to 699 in the system so at a tank elevation of 779, our static pressure is 35 psi ( at high ground elevation of 699).

  • Hello,

    I would recommend taking a look at this wiki, which has information on the operating range for a tank: Understanding Tank Operating Range. The minimum elevation would be the lowest level of useable water for the simulation. If the elevation in the tank reaches this value, that would mean that the tank is empty.

    Regards,

    Scott