Deposit Gauges and Copper Sulphate Solution

Deposit gauges are provided with copper sulphate solution to prevent the growth of algae.

Algae can grow in water, and if it grows too much, it can clog the gauge and make it inaccurate. Copper sulphate is a toxic substance to algae, so it prevents them from growing.

The answer to the question “Why are deposit gauges provided with copper sulphate solution?” is therefore “To prevent the growth of algae.”