Converting an Open-Vented System to Sealed
Converting removes the feed and expansion tank from the loft and puts the heating circuit under pressure, with an expansion vessel and a filling loop instead.
Converting removes the feed and expansion tank from the loft and puts the heating circuit under pressure, with an expansion vessel and a filling loop instead. It is usually done alongside a boiler change and it tests every joint in the house.
Why old systems leak afterwards
An open-vented circuit runs at near-zero pressure. Raise it to a bar and tired compression joints and corroded radiator valves start to weep.
What gets added
Expansion vessel sized to system volume, pressure relief with a safe discharge, a gauge, and a means of filling that meets water regulations.
The honest warning
We will always say before starting that a conversion can expose weak joints. It is not damage caused by carelessness, it is age revealed by pressure.
Discuss a sealed system conversion
Tell us the age of the pipework and radiators and we will be straight about the risks before any work starts.
Questions we get asked
Can the loft tanks be left in place?
The feed and expansion tank must be disconnected. A cold water storage tank may remain if the hot water side still needs it.
Does it improve hot water pressure?
Only if the hot water side is also changed. Sealing the heating circuit alone does not affect the taps.
Will old microbore survive it?
Often, but it is exactly the pipework most likely to show weaknesses once pressurised.