Hello,
I have a 08 2500 with a 6.7 CTD. My question is; How often do you drain water from your fuel filter, and have you had any problems getting the drain valve to seal afterword? (The manual says to drain once a month.)

 

I rarely drain mine. The secret is to buy quality fuel, not the cheapest cutrate price you can find. Big rigs don't even have drains, and they use a lot more fuel than we do.
If it makes you feel better, drain it when you check the oil.

 

if it leaks just work the handle a few times. if it don't stop then take it apart and clean it out the add grease put back together. to take apart under the handle is a plastic nut unscrew that then pull the plunger out. clean grease put back in.
the plastic nut use your hands anything else you risk breaking it and Cummins don't normally stock that. atleast my location don't unless they got wise to me breaking them all the time lol
Pizzo

 

I've only drained mine when replacing the fuel filter.