A common problem labs have is that the filter housing (bowl) gets tightened too much when the Ion-Ex or 1 Micron filters are changed and the next time they need to be replaced it seems like it is impossible to loosen it.
When doing up the bowl make sure the O-ring is in place and has not fallen out, without the O-ring the filter housing can seize as there is little give in the head and it plastic on plastic.
Bowls should only be done up by hand. The seal is provided by the O-ring, so it should be replaced if it does not seal when don up hand tight. The black spanner is intended for for loosening the housings.
IMPORTANT: If the bowl is over tightened they can crack as the styrene material it is made from can be quite brittle.
