A cavity wall insulation pump is the machine that blows fill through a hose into a drilled cavity, and the way it is used is most of what decides whether a wall is properly insulated. The material is metered and blown under pressure through holes drilled in a pattern across the elevation, working in a sequence that fills the cavity from the bottom up. A wall filled from too few holes, or too quickly, has voids in it that nobody can see.
The drilling pattern is the specification
Holes are drilled in a grid across the wall, usually in the mortar joints, at spacings set by the system being installed. Too few holes and the fill cannot reach the whole cavity; the pattern is not a matter of tidiness but of whether the wall ends up insulated.
Filling from the bottom up
The installer works upward so that fill settles into place rather than bridging and leaving voids beneath. Around openings, at the top of the wall and beside obstructions are where voids form, and those are the areas a thermal image will later show as cold.
Making good, and what to check
Holes are filled with a matching mortar and should be barely visible on a weathered wall. Before the team leaves, ask for the installation certificate, the guarantee registration and confirmation that airbricks and flues were sleeved or protected, because blocking one is the failure that causes real harm.
Questions people ask about cavity wall insulation pump
Can I see whether the fill is complete?
Not by eye. A thermal image taken in cold weather shows voids clearly, and it is the evidence to ask for if a wall stays cold after the work.
What happens to airbricks and flues?
They must be kept clear, normally by sleeving before the fill goes in. A blocked airbrick under a suspended floor causes damp and rot, and a blocked flue is dangerous, so this is worth confirming rather than assuming.
How long does the work take?
Filling a typical house is usually a single day for the fill itself, with the survey done earlier. The short duration is one reason this measure is the one government backed schemes have funded most widely.