Red Diesel & Belgium

To confirm I drain the tank by taking the inspection cover off and pumping the tank dry. I have a 12volt pump that is also used for filling the tank, it is far easier to pump from cans to tank than try to hold the cans over the filler. this pump is used to empty the tank.
I have never had a problem with the seal, if there is a problem then will buy or make a new one.
The old oil is burnt off in our domestic boiler.
To any one serious about fitting twin tanks, presumably the main incentive is cost; the cost of fuel from a normal vehicle filling station and red from a marina is not much different. The fuel from a filling station is fresh and stored for very little time , some marina supplies are not filled very often, I often fill up with a couple of cans from my local station rather than use red, then no problem on continent.
By way of another though red diesel or gas oil is not long for this world the new duty free is green dye and made to the same spec as road derv, that having a higher water content and a shorter storage life, so as a thought maybe you should look to bye the green dye fuel that is being used in agriculture, that may confuse the Belgians .
Simon