Leaving a site

10kg is neither here nor there in the grand scheme of things.

Draining in cold conditions to protect against frost damage is a different matter but in good weather I don't see a need. 

I always drain down the water tank when leaving a site. I don't like the thought of the water sloshing about and the weight too. It only takes a few seconds. We are also probably at the limit of our payload everytime out.

I drain my hot water tank each trip. It's 'only' 10kg, but its towards the front of the caravan & my car's nose weight max is only 85kg.

I usually drain my water just as I've left the site

A split decision! We had cars with higher noseweight limits and vans with ample payload but I wonder how many people consider the extra weight when the throw a full awning and poles into the van?

Ours go into the back of the car .... I suspect many others do the same

We also drain down each time we move. However, although this may not be entirely necessary, the instructions with Alde heating say it should be done every month, to preserve the air cushion in the boiler. Given the cost of the system, I prefer to follow this advice.

And many don't unless it's so they can carry the table, chairs and bikes inside the van

Back to the idea of packing up.  I find it a bit of a long job to do all the necessary on the morning of departure, so I have taken to doing some the day before, such as not refilling one of the Aquarolls when it runs dry, putting magazines and CD away in lockers when last one finished with.  It eases the rush and allows a leisurely departure, even a walk around the vacated pitch to collect the things that fell under the 'van but were not missed!

We never drain down when touring just when we start the journey home.  Never had a problem with weight or stability