I run it at 10 psi.
Less psi does not mean better filtration.
More psi tends to rip cartridge apart.
Canister usually does not leak unless canister gasket is off
![Smiley :)](http://www.homebrewersassociation.org/forum/Smileys/default/smiley.gif)
Try your local plumbing supply store (box stores do not have them) and ask for 1 micron sediment filter.
Do not get the carbon stuff.
They are about $27.
You could go with disposable type.
They are about $2 on web.
Lookup 1 micron cartridge on Northern brewer site and then search for the brand they are selling.