Plumbing Glossary

Distribution unit: one feed — several loops with valves/flow meters. Basis of home-run piping.

Tightness test at elevated pressure (usually 1.5× working) before concealing pipework.

Set on the boiler supply: 3-bar relief valve, auto air vent, pressure gauge.

Membrane vessel absorbing thermal expansion. Sized ≈10% of system volume.

Assembly with a 3-way valve and pump feeding underfloor at 35–45°C from a 60–80°C boiler.

Vent extension of the soil stack above the roof — protects traps from siphonage.

Pipe bend holding water that blocks sewer odor. Dries out if unused for long.

Hatch for drain cleaning or node access. Must never be walled over.

Each point gets its own pipe from the manifold — no joints in screed. Reliable but more pipe.

One main line with branches. Cheaper on pipe, but joints get buried and balancing is worse.

Vessel decoupling boiler and consumer circuit hydraulics when multiple pumps run.

Valve with a head that self-throttles radiator feed to a set room temperature.

Lets flow pass one way only. Fitted on makeup lines, after pumps, on DHW recirculation.

Manual bleeder at the top of a radiator/loop to release trapped air.

Valve cutting inlet pressure to a setpoint (usually 3–4 bar) — guards against water hammer.

Dissimilar-metal contact (copper+galvanized) in water → corrosion. Break with dielectric unions.