Cornish Cream just posted a link to the TM31 Manual on another thread so I thought I'd have a quick read as I don't think I've referred to mine since I got the machine.
I found 2 interesting things about the Varoma
1. It says not to use above speed 2 to avoid splashing liquid into the tray
2. For quantity of water it says: 30 minutes steam cooking requires 0.5 litre (500 g) of water, for every additional 15 minutes an additional 250 g.
HTH