Desludging pumps can be turned on and off with a timer but it is more efficient to use a controller based on suspended solids. The Markland Model 502 suspended solids controller can be used to measure this slurry and then control the pumps. Markland offers free testing of your materials. Using safe ultrasound, the meter can be used in open top tanks or in pipelines. It measures slurries too thick for optical methods.