I have a whole house carbon filter on cold water line to kitchen. It is mounted in utility room. The outlet fitting threads leak unless I put filter in bypass. But outlet fitting sees full pressure in bypass. Why does it leak in "filter" mode? We are on city water. But we have 25 grains of hardness. Water tastes ok. I use filter cuz I think it works. I know it does little to nothing for hardness. It is 10 yrs old. Has leaked for 3-4 yrs. so it has been in bypass since. Should I just remove it? Easy enough. Or try and put new Teflon tape on threaded fittings?