I know I put this in the general section but I'll put it here as well.
Don't leave bits of kit you have replaced lying around at the customer's place as it's bad practice. One local engineer I come across seems to leave debris and junk with customers and today I was presented with a shoebox of worn out oil pumps, used flexi hoses, nozzles, bust control box, broken solenoid etc. Fair enough if something still functions (such as an old nozzle, but only one), leave it there, but otherwise If you replace something faulty, show it to the customer and ask if they would like you to dispose of or recycle it for them. If they say they want to keep it, fair enough, otherwise take your junk away with you.
It is one of my main pet hates, tradesmen leaving junk for me to clear away, whether they be electricians, joiners, plumbers etc. Wire trimmings, empty PTFE spools, rubble etc swept under floorboards really annoys me. I only use tradesmen for my own jobs who are tidy. Came to one property and there were half a dozen old flexi oil lines tied around a horizontal pipe like dead moles on a molecatcher's gibbet, totally ridiculous.
In industry for commercial work, it is an absolute no-no to leave junk on site and if you do so, the customer will take a dim view of it. Domestic is no different. There's also a potential liability risk if you leave a broken component and someone later tries it and something goes wrong, they could blame you.
On another note, as a previous post has said, make it obvious what you take off is useless by breaking it so it can't get mixed up with good stuff again. I always bend old immersion heater stats in half for example as soon as I take them out.
I worked in a printing works once. In the past, a plumber had left a short pipe offcut on a gantry which months later had accidentally been knocked off and fell into a printing press, causing thousands of pounds worth of damage.
