Determining head when selecting a water pump

Determining height ( HEAD ) when selecting a water pump

" But when we need to choose water pump to deliver water to an elevated location, we can read the pump curve or its head rating. " 
Many readers are probably familiar with this, but the difficulty is knowing the actual elevation of the destination. Here is a simple way to estimate it.

1. For an existing pipe route, the actual delivery-point height can be estimated by fitting a pressure gauge at the pump and pumping normally. After stopping the pump, water remains in the pipe; its pressure, in kilograms per square centimeter, indicates the delivery height.  

 

Using bar for comparison, 1 bar is close to 1 kilograms per square centimeter, corresponding to a vertical height of 10 approximately. The values differ slightly, but an approximate comparison is sufficient here. In practice, if the water in the pipe presses on the gauge after the pump is stopped and the gauge reads 1.5 bar or 1.5 kilograms per square centimeter, that is equivalent to a height of 15 meters: the highest elevation the water must reach is 15 meters. Examples include delivering water to a champagne-shaped elevated tank or a garden storage tank. A pressure gauge can be used for both vertical and sloping pipe routes.
But what if there is no pressure gauge? ??
We often hear about pumping water up a steep hillside at 45 degrees or 30 degrees. Such slopes are very steep and are uncommon; some areas do not have slopes this steep. Sometimes, however, the route has a slope of 87-90 degrees for tens of meters, for example pumping at 90 degrees to a height of 57 meters in several districts of Chiang Rai. Such descriptions are common, but the actual slopes observed may be less steep. Measurements have sometimes shown 77 degrees or 82 degrees, which is fine.   Sometimes residents are concerned about pumping up steep terrain and estimate the slope incorrectly, making pump calculations more difficult.   For example, they describe a hillside with a pipe route of 50 meters, inclined at 45 degrees along the hillside. When drawn to scale on paper, the actual height above the pump position is only 34 meters. Adding a suction lift of 8 meters and a further tank delivery height of 10 meters gives a total height of only 52 meters. When asked whether this is equivalent to a 20 story building, the site owner shakes their head and says it is no taller than a 5 story building. Discussion then reveals that slope angles are usually estimated roughly rather than measured accurately. Such estimates can easily be wrong. Use a protractor, or an angle-measuring tool like the one pictured, aligned with the pipe route or sight line to the destination. This makes a scaled paper model easier to create, as illustrated.

Smartphone users can also download a protractor application   and place the phone along the pipe route toward the delivery point. The approximate angle can then be transferred to a scaled drawing to calculate the height.

 

Steps for estimating pump head