Installation manual

4. Designing your site layout and choosing your turbine model

4.1. Measuring Head

You will need to measure the vertical drop in feet or meters (referred to as head or fall). A

map with contours can be useful for initial feasibility study followed by a site survey using the

methods below. It's a good idea to use more than one approach, so you can check

accuracy.

Altimeter - obtain an altimeter accurate to 10 feet (3m), this is good for measuring falls

greater that 70 feet (20m). Take the average of several readings. Some modern hand-held

GPS instruments that are fitted with internal altimeters can read altitude to 1m if the air

pressure is stable during the survey.

Builder’s optical level ("sight level") - measure the fall between intake and turbine in steps as

you progress along the pipe route. This is good for lower falls and it is very accurate. You

can use the height of the spotter's eye level as a unit of measure and move up the slope in a

series of equal steps. Use a helper to mark the spot, or simply keep your eye on that spot

until you are standing on it ready to sight the next one.

Low cost laser level - at dusk or in low light conditions project a horizontal beam and using a

long staff measure the vertical drop, as you progress down alongside the stream. You may

have to repeat this at a few locations.

Pressure gauge - lay a length of small bore plastic pipe or hose, fix a pressure gauge to the

end and measure the pressure of the water with the pipe full. 14.5 psi is 33 feet of fall (100

kPa is 10m of fall). Make sure you clear the line of all air first. This is a very accurate method

and easy to do.

Click here for a recent Home Power article on how to measure the head.