I had already updated mekanism to lastest build, i had put some Mechanical pipes and boom!
http://pastebin.com/w8dVk3vF

I'm afraid I can't tell why that's happening because I can't see ic2's source code. We're not passing any null arguments to their method that's crashing though, so I don't see why it would happen.

public boolean canDrain(ForgeDirection from, Fluid fluid)
{
359 if ((from.getOpposite().ordinal() == getFacing()) || (from.ordinal() == getFacing())) {
360 return false;
}
361 return this.distilledwaterTank.getFluid().isFluidEqual(new FluidStack(fluid, 1));
}

That looks like an ic2 issue, report it to them I guess.