What Does an Emergency Plumber Actually Do?
By Emergency Plumb,

What the job involves, what to expect from a good one, and the questions worth asking at the door.
Short answer: An emergency plumber stops active damage and restores essential services the same visit: burst and leaking pipes, blocked drains and toilets, and loss of hot water or heating. The job is to stabilise first and repair properly second.
The job in one line
Stop the damage first, then repair the cause: isolate the water or gas, make the situation safe, and only then fix, quote or advise. An emergency plumber who starts with paperwork has the order backwards.
What a good one looks like
Answers the phone directly, gives an honest arrival window, talks you through making safe while the van moves, shows ID, states a price before working, and leaves the paperwork your insurer will ask for.
What you should never see
A price that appears after the work, pressure to decide instantly, cash-only demands, or reluctance to give a company name. Any one of those is a reason to close the door.
What counts as an emergency
Water you cannot stop. Water near electrics. No water at all. No heating in freezing weather with a vulnerable occupant. A single blocked toilet in a one-bathroom home. Those warrant a callout at any hour, and we would rather you rang for one than waited.
What sensibly waits until morning
A dripping tap, a slow gully, a radiator that is cold at one end, a running toilet, or a booked job you have been putting off. Nothing is gained by paying attention to these at 3am, and an honest firm will tell you so on the phone rather than dispatching a van. For the wider picture of the trade, see the meaning of plumbing work and the jobs it includes.
What happens on the call itself
A controller establishes what has failed, talks you through isolating it, gives you a real arrival time for your postcode, and confirms the rate before anyone sets off. The advice given in that first two minutes, stopcock off, electrics off, taps open, routinely prevents more damage than the visit itself does.
If it is happening now, our emergency plumber in London page has the number and the rate before anyone sets off.
Questions people ask
What is the difference between an emergency and a normal plumber?
Availability and priority, not skill. The same engineers do both. An emergency call-out means dropping planned work to attend now, which is why emergency-only firms often charge a premium - and why a firm doing both can price them the same.
Will they fix it there and then?
Usually. Where a part is obsolete or the fault needs a specialist survey, the first visit makes the property safe and stops the damage, and the repair is booked. Making safe is still the visit doing its job.