sealing Ball Valve assemblies

My first AG batch went very well this weekend - pumped!!

I've got verrrry slow drips coming from both my mash tun (10 gallon cylindrical cooler) and my kettle (15 gallon Megapot) at the ball valve assemblies.  The assembly on both is just like this one:

https://www.google.com/search?q=homebrew+ball+valve+assembly&source=lnms&tbm=isch&sa=X&ei=HkhNU8nROsrSsATnsoAw&ved=0CAcQ_AUoAg&biw=1280&bih=939#facrc=_&imgdii=_&imgrc=ZsQv8F88LQw6BM%253A%3Bzf_y-u3YV1SEiM%3Bhttp%253A%252F%252Fwww.homebrewing.org%252Fassets%252Fimages%252Fstainless_steel_weldless_kettle_conversion_kit_with_ball_valve_angle_one.jpg%3Bhttp%253A%252F%252Fwww.homebrewing.org%252FStainless-Steel-Weldless-Kettle-Conversion-Ball-Valve-Assembly_p_2380.html%3B450%3B357

interior, round female piece, washer, o-ring, kettle/cooler wall, o-ring, nut, ball valve

I've cranked on this assembly about as hard as I possibly can.  Should I be looking for perfection or is a drip rate of about .25-.5 pint throughout the entire brewing process just bound to happen?  Any suggestions?

Mine leaks really slowly too.  I don't have as much leakage as you do though.  On my MLT's I get maybe 30 drips during the entire process.  On my boil pot, I never see it leaking, but there is always a little trickled down carmelized string where it obviously leaked out very, very slowly.

My leaks are small enough that I don't let it worry me.  A .5 to 1 pint seems like a lot.  I'd lock it down a little tighter, if you can.

Thanks Scott - I don't think I'm anywhere close to 1 pint, but I'll put some elbow grease into them for the next batch 

Tighter is not always better when using O-rings or rubber washers. I followed the process described in http://www.theelectricbrewery.com/

The parts allow the O-ring to seal against the valve body and the kettle, but prevent the ring being distorted. No leaks, no problems. The link provides a parts source and part numbers.

Good thought - I probably have distorted the O rings when cranking on the assembly.  Something to watch for indeed.