Why you should check your dumpy level weekly.
Using any piece of equipment that you haven’t checked could lead to disaster. Using a dumpy level that hasn’t been checked can lead to a costly mistake. Take the case of a site engineer working on a new proposed surface water drainage network for a new proposed access road. After setting out the new manhole positions along the new proposed road, the site engineer proceeded to work out profiles for the drain runs. Each time he set up his dumpy level he was next to the downstream manhole and took readings to the upstream manhole. But because he hadn’t checked his dumpy level, he didn’t realise that it was falling by 20mm over 30m. He also didn’t close his levelling run so had no other clues as to the accuracy of his results. As the drainage works progressed, the pipe runs were installed lower than the design levels. The mistake was only noticed when the cover and frames were being installed and the drainage crew were using more raising pieces than expected, and in the worst case an extra manhole ring was needed to be installed.
Top Tip for Getting the Best Results When Checking Levels.
Whenever you are checking an Automatic (Dumpy) Level, or a Rotating Laser Level, or a Total Station, make sure that the tripod head is as close to being level as possible. Whenever I am carrying out these checks I like to use a bullseye spirit level like this one I bought from Amazon. Its 65mm diameter so it spans the tripod access hole and is large enough to be easy to set.