Roofing iron Wellington

[Robin McCandless]

You could have emptied the 40l of water with a flexible plastic hose (syphon it down into a bathroom, just like syphoning petrol from a car petrol tank into a plastic cannister).

Needs 2 people (one to suck at the bottom and one to hold the hose underwater at the top.

[Viking]

Unless the iron is really bad just rust coat the bits that are rusty and re nail and repaint. The iron that's on there will last many more years than the new stuff especially if salt spray is anywhere around.
There is also a product that's been around since ww2. Name I can't recall but its made of wood fibre. Good stuff, doesn't rust, light and makes the house a lot quieter.

There are also several spray on membranes that can be used. Check out the yellow pages under roofing.