Regulate a 12V Water Pump with a Motor Speed Controler (PWM)

During our trip to New Zealand, we bought a little Camper Van. For some reason, the built-in water pump had too much power so that the water shot out of the tap and splashed everything around it.

To restrain the pump, one could probably install a resistor. But resistor burn off unused current as heat and therefore are inefficient. Also, how much resistance is needed to slow down the pump to a desired level?

Another possibility is a Motor Speed Controller based on Pulse-Width-Modulation (PWM). This controller allows you to vary the output from 0 to 100%, which makes it easy to find the ideal configuration. Motor speed controllers can also be used as LED dimmers! That is the solution I settled for the van and it worked out great.

The installation looks a bit messy. But hey, it just for a year (and it was messy before).