There are clear differences on who is responsible here. We can expect a factory to be always responsible over their area as it is a larger entity and doing business and we expect them to be experts and be in control of their own domain. We can expect them to be responsible over their non skilled labourers.
A plumber is the expert in this case and he controls his domain while you are just a dumb customer.
That's why it's not simple - you've got lots of things open to debate there - who is skilled or unskilled, who is a business, who is a 'larger' entity, who is the expert. That's why it's more complicated than just saying 'yes' with an emphatic full stop.