FAULTNEST PLUMBING

Plumbing Fault-Finding Guides

Diagnose common plumbing problems involving leaks, blocked drains, toilets, taps, showers, pipes, water pressure and hot water systems. Start with the exact symptom and work through the simplest checks first.

!

Stop water damage before troubleshooting

If water is escaping quickly, turn off the nearest isolation valve or the main stopcock before investigating. Avoid electrical fittings, ceilings containing lights and any area where water may have reached live equipment.

Read FaultNest plumbing safety guidance →

BROWSE PLUMBING FAULTS

Choose the plumbing problem

Open the section that matches the symptom, then choose the individual troubleshooting guide.

Leaks and dripping water Pipes, joints, ceilings, valves, appliances and hidden water leaks.
Pipe Leaking Identify the source, isolate the water and assess the damaged joint or pipe. Pipe Joint Leaking Check compression fittings, push-fit joints, soldered joints and seals. Water Leaking Through the Ceiling Trace bathrooms, tanks, heating pipes, roofs and hidden plumbing above. Water Leak Under the Sink Check traps, tap tails, isolation valves, waste joints and appliances. Water Leak Behind the Toilet Inspect the inlet valve, cistern connection, flush pipe and pan connector. Radiator Valve Leaking Check the gland nut, compression joint, valve body and radiator tail. Washing Machine Hose Leaking Inspect inlet hoses, waste hoses, washers and appliance connections. Dishwasher Hose Leaking Check supply hoses, drain hoses, clips and cabinet connections. Signs of a Hidden Water Leak Recognise meter movement, damp patches, pressure loss and unexplained water use. Stopcock Leaking Check the gland, spindle, compression joints and valve body.
Blocked drains and slow waste Sinks, baths, showers, toilets, outside drains and recurring blockages.
Sink Draining Slowly Clear traps, grease, food debris, soap deposits and partial pipe blockages. Sink Completely Blocked Work through plunging, trap removal, drain snakes and pipe checks. Bath Draining Slowly Remove hair, soap deposits and restrictions around the trap and waste pipe. Shower Drain Blocked Clean the waste cover, trap and connected pipework. Toilet Blocked Clear paper and object blockages without damaging the pan or seals. Toilet Keeps Blocking Check restricted drains, poor flushing, scale and incorrect pipe falls. Outside Drain Blocked Inspect gullies, traps, rodding points and shared drain problems. Multiple Drains Blocked Recognise main drain or shared sewer restrictions. Drain Gurgling Check partial blockages, venting issues and trapped air. Bad Smell From a Drain Check dry traps, debris, failed seals and drain ventilation.
Toilet and cistern problems Running water, weak flushing, filling faults, leaks and noisy cisterns.
Toilet Keeps Running Check the flush valve seal, fill valve, water level and overflow. Toilet Won’t Flush Inspect the button, handle, cable, siphon and flush valve. Toilet Flush Is Weak Check cistern water level, rim holes, siphon performance and blockages. Toilet Cistern Not Filling Test the isolation valve, fill valve, float and supply pressure. Toilet Cistern Fills Slowly Check restricted valves, filters, scale and low water pressure. Toilet Keeps Filling Diagnose fill valve faults, incorrect float settings and leaking flush valves. Toilet Leaking at the Base Check the pan connector, floor fixings, condensation and cistern leaks. Toilet Button Not Working Inspect button mechanisms, cables and pneumatic tubes. Toilet Handle Loose or Not Working Check the lever, retaining nut, linkage and siphon connection. Toilet Making Noise Identify whistling, humming, water hammer and fill valve vibration.
Tap and mixer faults Drips, stiffness, poor flow, temperature problems and noisy taps.
Tap Keeps Dripping Check washers, ceramic cartridges, valve seats and O-rings. Tap Leaking From the Base Inspect cartridge seals, body O-rings and loose tap fittings. Tap Leaking Under the Sink Check flexible tails, copper connections, isolation valves and fixing studs. Tap Hard to Turn Diagnose scale, seized cartridges, worn valves and damaged handles. Tap Handle Loose Check retaining screws, splines and cartridge stems. Low Flow From One Tap Clean aerators and check isolation valves, cartridges and flexible hoses. No Water From One Tap Check local valves, blocked cartridges and frozen or restricted pipes. Mixer Tap Temperature Problem Diagnose cartridge, pressure balance and supply connection faults. Tap Making Noise Identify loose washers, high pressure, water hammer and vibration. Outside Tap Leaking Check washers, glands, frost damage and pipe connections.
Shower and bath plumbing Low pressure, temperature changes, leaks, dripping and poor drainage.
Shower Pressure Low Check the shower head, hose, filters, valves and water supply. Shower Temperature Keeps Changing Diagnose thermostatic cartridges, pressure imbalance and boiler flow issues. Shower Only Produces Cold Water Check hot water supply, mixer cartridges and electric shower heating faults. Shower Only Produces Hot Water Check cold supply restrictions and thermostatic mixer faults. Shower Head Keeps Dripping Inspect control valves, cartridges and retained water in the head. Shower Hose Leaking Check washers, split hoses, loose nuts and damaged threads. Shower Leaking Through the Ceiling Inspect trays, seals, waste fittings, pipe joints and tiled areas. Bath Waste Leaking Check waste seals, overflow connections and trap joints. Bath Tap Leaking Inspect tap valves, flexible tails, deck fittings and pipework. Shower Tray Leaking Separate sealant failure from waste, tray and pipe leaks.
Water pressure and flow problems Low pressure, high pressure, weak flow and sudden supply changes.
Low Water Pressure in the House Check the mains supply, stopcock, filters, leaks and pressure controls. Low Water Pressure Upstairs Assess system type, static head, restrictions and pump performance. Low Hot Water Pressure Check cylinders, boilers, filters, scale and hot-side restrictions. Low Cold Water Pressure Check mains pressure, valves, filters and local pipe restrictions. Pressure Drops When Two Taps Open Assess supply capacity, pipe sizing and shared restrictions. Water Pressure Too High Recognise banging pipes, failed valves and pressure-reducing valve faults. Water Flow Pulsing Check pumps, blocked filters, air and unstable supply pressure. Water Stops Then Starts Diagnose intermittent supply, valve and pump problems.
Noisy pipes and water hammer Banging, humming, rattling, whistling and vibration in plumbing systems.
Pipes Banging Identify water hammer, loose pipe clips and rapid valve closure. Water Hammer Check pressure, solenoid valves, pipe support and arrestor options. Pipes Humming Diagnose high pressure, vibrating valves and partially closed stopcocks. Pipes Whistling Check restricted valves, worn washers and high-velocity flow. Pipes Rattling Find loose clips, pipe expansion and contact with floors or walls. Gurgling Pipes Check drainage ventilation, partial blockages and trapped air. Noise When the Toilet Fills Inspect the fill valve, pressure and pipe vibration. Bang When a Tap Turns Off Identify water hammer and unsupported pipework.
Hot water plumbing faults No hot water, slow delivery, temperature faults and cylinder problems.
No Hot Water Check boiler, immersion, cylinder, controls and hot water supply faults. Hot Water Runs Out Quickly Assess cylinder capacity, thermostat settings, immersion and heat-up time. Hot Water Takes a Long Time to Arrive Check pipe runs, circulation systems and flow restrictions. Hot Water Not Hot Enough Check thermostat settings, mixing valves, boilers and scale. Hot Water Too Hot Inspect thermostats, mixing valves and control faults. Hot Water Cylinder Leaking Identify connection, valve, immersion and cylinder-body leaks. Overflow Pipe Dripping Check float valves, expansion vessels, pressure valves and overheating. Tundish Dripping Understand discharge from unvented hot water safety valves.
Frozen pipes and cold-weather faults No water, split pipes, frozen outside taps and winter leaks.
Frozen Pipe Locate the frozen section and thaw it safely without flame or excessive heat. No Water During Cold Weather Check exposed pipes, loft tanks, external supplies and frozen stopcocks. Burst Pipe Shut off the water, drain the system and limit property damage. Outside Tap Frozen Thaw safely and inspect the tap and pipework for splits. Pipe Leaks After Freezing Check split copper, failed joints and damage hidden by insulation. How to Prevent Frozen Pipes Insulate vulnerable pipework and protect lofts, garages and outside taps.
Plumbing checks and repair basics Isolation, tools, testing and simple plumbing reference guides.
How to Turn Off the Water Supply Find and use the main stopcock and local isolation valves. How to Find a Water Leak Use visual checks, meter tests and isolation to narrow down the source. How to Use a Plunger Correctly Create an effective seal and avoid pushing blockages deeper. How to Clean a Sink Trap Remove, clean and refit a bottle trap or P-trap without leaks. How to Check Water Pressure Measure static and dynamic pressure and interpret the result. Plumbing Tools for Home Repairs Useful spanners, grips, cutters, plungers and leak-control equipment. When to Call a Plumber Know when a plumbing fault is unsafe, hidden or beyond a basic repair. Emergency Water Leak Checklist Immediate steps to isolate the supply and reduce property damage.

CAN’T FIND THE EXACT FAULT?

Search the complete FaultNest library

Use the search box in the navigation menu. Every plumbing guide added to the sitemap becomes searchable automatically.

View safety guidance