A plumber
Plumbers commonly repair water pipes, taps, toilets, basins, baths, showers, radiators, tanks and water-side heating components. They may also install bathroom fittings and alter water supplies and wastes inside the property.
A drainage specialist
A drainage specialist may be better suited to a blocked or damaged drain, repeated external blockages, drain surveys, tree roots growing into drains or faults in underground waste pipes. If only one sink, basin or toilet is affected, an internal plumbing blockage may still be the likely starting point.
Responsibility for drains and sewers can change at the property boundary or where pipework is shared. Your water and sewerage company can explain the arrangement in your area.
A Gas Safe registered engineer
Work on a gas boiler, gas fire, cooker, gas pipe or other gas fitting must be carried out by a Gas Safe registered business and an engineer qualified for that category. Some plumbers are Gas Safe registered; others are not. Check rather than assume.
Water-side radiator and pipework jobs may not be gas work, but any job that involves opening, repairing or connecting a gas appliance needs the appropriate registration.
Gas or carbon-monoxide emergency
If you smell gas, avoid flames and do not operate electrical switches. Open doors and windows if you can do so safely, go outside and call the gas emergency service: 0800 111 999 in England, Scotland or Wales, or 0800 002 001 in Northern Ireland.
Carbon monoxide has no smell. If you suspect poisoning, go outside, get medical help immediately and do not return to the building until you have been told it is safe. If a gas appliance may be involved, call the gas emergency service as well.
Call 999 if someone may have been exposed and is having difficulty breathing, suddenly confused, unconscious, weak, or has chest or muscle pain. Do not drive yourself to hospital.
For other suspected symptoms in England, Scotland or Wales, call 111 for urgent medical advice. In Northern Ireland, seek medical help immediately; NI Direct advises going to an emergency department if you have symptoms after suspected exposure. For further details, read the NHS carbon-monoxide guidance.
Do not use a quote form or wait for tradespeople to respond in an emergency.
Sources and further information
External guidance can change. Follow the linked organisation where its advice applies to your situation.