Plumbing is a licensed trade here, not a favour from the building watchman
In the UAE, what matters is not a personal plumbing licence but the company behind the technician. A legitimate plumbing outfit holds an economic licence from the emirate's licensing authority — the Department of Economy and Tourism in Dubai, ADDED in Abu Dhabi, the economic development departments elsewhere — with an activity such as plumbing and sanitary installation or building maintenance listed on it. The person in your bathroom should be a sponsored employee of that company, and when work goes wrong — a joint fails inside a wall three weeks later, a heater connection drips into the flat below — your recourse runs through that company, its licence and its insurance.
A freelancer moonlighting from an unrelated job has no licence, no insurance and, practically speaking, no address. If his joint floods the apartment beneath yours, the claim lands on you as the person who hired him. The gap between a licensed company and an unlicensed handyman on a mixer swap might be AED 50–150; the gap when a concealed connection fails is a collapsed gypsum ceiling, warped wardrobes and a five-figure bill in dirhams. Compliance is the cheapest insurance you will ever buy.