Instructions – Correct Installation of Capillary Tube
A capillary tube (sometimes called a “breather tube”) is a narrow tube that is inserted into the spacer between the two panes in a dual-paned window. The capillary tube equalizes the pressure inside and outside the sealed unit.
This is especially critical when shipped by air freight, as air pressure diminishes at higher altitudes. Likewise, it’s important when shipping dual-paned units to high-altitude geographical locations.
You can see the capillary tube sticking out from an outside corner of your dual-paned window unit.
For windows that are to be installed vertically, seal the tube (a) with a drop of silicon sealant on the opening, (b) during mild weather of 50 to 70° F, and (c) with the window unit standing vertically.
When installing the window, always ensure that the capillary tube is at the top of the window, pointing down. Never install with the tube at the bottom of the window.
If tube must be cut to facilitate installation, steps (a), (b), and (c) still apply.
The same instructions apply for dual-paned horizontal (e.g. skylights) or sloped installations as for vertical installations, though position of the tube at installation is not critical.
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