I am a pump and pressurisation engineer/salesman. I look at boosting water up tall buildings, football stadiums, schools etc, storing water and distribution through pipework. Most calulations are based on flowrates, resistances through pipework, weights etc. The other part of the business is heating pressurisation so dealing with expansion at different temperatures and how to deal with it.
It's a great job and you have to think on your feet whilst in meetings with clients. I tend to do the maths in my head and then check it on a calculator, when the answer is correct I say to the customer "I could do this for a living..!!" When I get it wrong, I blame the calculator.....
H.