Jargon Buster - O

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The component in a compression fitting that provides the mechanical seal.

One-pipe system

Where the radiators are run in series, with the flow in and return out on the same pipe.

Open safety-vent pipe

The part of a conventional tank-fed un-pressurised central heating system that allows any pressure build up to be safely discharged to the atmosphere.

Open-vented system

A conventional central heating system which is un-pressurised and tank fed.


A device that collects temperature data from sensors inside and outside the building, allowing the boiler to work at maximum fuel efficiency.

Outlet valve

An isolation device to control substances leaving an appliance.

Overflow pipe

A device fitted to a tank to safely discharge surplus water.


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