Foam markers and tanks filling devices transcript
Since the development of GPS and autospray technology, foam marking has fallen out of favour. It does though pay to maintain a functioning foam marker as it does provide some back-up in the event of the technology letting you down. Foam markers are a useful tool to identify where you started spraying.
The mixing hopper can be used as a measuring device. Inflow meters are used to flow water into the sprayer but these must also be calibrated as well. The hopper can be used as a back check on the inflow meter. If your hopper holds, say 50 litres to the point of overflow with water, and you use a different water source, like overhead gravity feed instead of your usual fire pump, you can run a hose back from your inflow to your hopper and fill the hopper.
By doing this you have a back check that the flow meter you're using to fill the sprayer isn't reading differently at different water sources. The inflow meter should read 50 litres at the point of overflow - this would be dead reckoning. Other readings would require a recalibration. Once the boom spray and inflow meter are both reading correctly, the sprayer's right to go.