Plumbing Terms Explained

Twenty four terms an engineer will use on your property, what each one does, and how you know when it has failed. Every entry links to the work it belongs to.

Acoustic leak detection

Listening for the sound a pressurised leak makes as water escapes a pipe. A ground microphone or contact probe amplifies it, and the position where the sound peaks is the leak. It is the first method tried on a buried or concealed supply line. See leak detection.

Thermal imaging

A camera that reads surface temperature rather than light. Water escaping a hot or cold line changes the temperature of the floor or wall above it, and the camera shows that pattern as a shape. Fast in a ceiling void, less certain through thick screed. Used in leak detection.

Tracer gas

A harmless gas mixture introduced into an emptied pipe. It escapes through the leak, rises through the floor, and is picked up at the surface by a detector. Reserved for leaks where acoustic listening is drowned out by traffic or a pump. See what leak detection costs depend on.

Isolation valve

A valve that cuts the water to one part of a property, or to all of it. Find yours before you need it. A valve that has not been turned in years often will not turn when it matters. See how to shut off your water.

Pressure reducing valve

A valve that steps incoming pressure down to a level the fittings can live with. When it drifts or sticks, one floor loses flow while the floor below it hammers, and relief valves start weeping. Often blamed on the pump. See low water pressure.

Booster pump

A pump that raises pressure for a building or a villa, usually drawing from a tank. Symptoms of failure are rapid on and off cycling, humming without rotation, or a leak at the shaft. Complaints reach you from the top floor first. See repair and replacement.

Expansion vessel

A small sealed tank beside a pump or heater, half air and half water, separated by a diaphragm. The air cushion absorbs pressure change. When it loses its charge, the pump cycles every few seconds and wears its own switch contacts out. See water pump repair.

Water hammer

The bang heard when a valve shuts fast and moving water has nowhere to go. It loosens brackets, works joints apart and eventually splits one. Usually caused by a solenoid valve in a washing machine or dishwasher snapping shut on an unsupported run. See pipe repair.

Backflow preventer

A device that lets water travel one way only, so a drop in mains pressure cannot draw contaminated water back into the supply. Required wherever an irrigation line, a boiler feed or a hose bib could siphon backwards. See backflow prevention.

PPR pipe

Polypropylene random copolymer pipe, joined by heat welding rather than glue or compression. Common in newer Dubai buildings. A correct weld is effectively one continuous pipe. A weld held a few seconds short passes handover and lets go later. See pipe materials compared.

PEX pipe

Cross linked polyethylene, supplied in long flexible coils. Because it bends around corners it needs far fewer joints than rigid pipe, which removes most of the places a system can fail. What remains is the crimped or pressed fitting at each end. See pipe materials compared.

Copper pipe

Durable metal pipe, tolerant of heat, still found throughout older Dubai properties. Its characteristic failure is a pinhole, forming where water sits still for long periods. Finding one pinhole usually means others are already forming. See pipe repair.

Galvanised steel pipe

Zinc coated steel pipe used widely before plastics. It scales inward year on year until the bore passes a fraction of what it once did. This is why an old villa loses pressure that no pump can restore. See pipe materials compared.

Dead leg

A length of pipe left connected but no longer used, usually forgotten after a bathroom was moved or a fitting removed. Water stands in it indefinitely. That stagnation is where copper pinholes tend to begin. See water leak repair.

Pan connector

The flexible sleeve joining the back of a toilet pan to the soil pipe. When it perishes, waste water seeps into the floor screed rather than onto it, so the smell arrives well before any visible stain. See toilet repair.

Fill valve

The valve inside a cistern that refills it after a flush and shuts off at the right level. When it stops closing fully, the cistern trickles into the pan all night, quietly, and nothing on the floor ever gets wet. See toilet repair.

Thermostatic cartridge

The temperature controlling core of a mixer shower. A wax element inside expands and contracts to hold the blend steady when pressure shifts. Scale seizes that element, and the shower starts swinging hot to cold. See shower repair.

Aerator

The small mesh screen at a tap outlet that mixes air into the stream. It is the first place scale lands, and a clogged one can halve the flow from a tap that is otherwise perfectly healthy. Ten minutes to clean. See low water pressure.

Anode rod

A sacrificial metal rod inside a water heater tank. It corrodes so the tank wall does not. Once it is consumed the tank begins corroding from the inside, and nobody notices until the cylinder body weeps. See water heater repair.

Thermal cut out

A safety switch on a water heater that latches off if the thermostat fails and the water overheats. A heater with no hot water at all, and no obvious fault, has often simply tripped its cut out. Resetting it without finding out why is a mistake. See water heater repair.

Pressure relief valve

A valve on a water heater that opens to release excess pressure. A steady drip from it points at the valve itself or at high incoming pressure, not usually at the tank. Diagnose before condemning the heater. See repair or replace.

Hydro jetting

Cleaning a drain with water at high pressure through a rear facing nozzle, so the hose pulls itself along while the jets strip the pipe wall. Unsuitable for pipe that is already cracked or displaced. See drain hydro jetting.

Belly

A section of drain that has sagged below the run, so water stands in it instead of flowing through. Every solid that passes settles at the low point. It reblocks however often it is cleared, under a kitchen or out in the main line. Found with a camera survey.

Sonde and locator

A transmitter in the head of a drain camera, and a handheld receiver above ground that finds it. Together they give a defect a position and a depth, which is the difference between digging once and digging three times. See CCTV drain inspection.

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