I have couple of pilsners in secondary. The carboys are not full to the top . Should I fill them ,top them up with water to eliminate headspace or leave alone?????........................Pat
How much headspace? A little is no problem as you will still get co2 from the yeast to fill up the space. If you have a lot and add water you will dilute your brew, just make sure to boil first if you do this. I would add CO2 into the secondary if that is an option for you.
Don't fill them with water. If it isn't too much it will be fine, the beer will still be giving off enough CO2 to clear out the space and there is enough alcohol in the beer now to not have big concerns about infection. If you have some CO2 you can always shoot a little in the space.