How to suction heating oil from a tank?

We have an old house that will be demolished soon and in the basement there are still plastic tanks with a remaining stock (approx. 400 l) of heating oil. We could use this heating oil well in another house. Is there a way to suction the oil and transfer it back into the other tank? Or is it better to wait until the basement is exposed during the demolition work and then somehow take care of it? Which companies do something like this?

There are certainly companies for that. Tank builders, tank cleaners - Ecosia should find that.
For the extracted liter, you might still get 40 cents. What it costs if they put it back somewhere else, I don't know.
Doing it yourself is a tricky thing: How do you want to transport the oil if not in a tanker truck? Driving around with everything in 20-liter gasoline cans is probably not the best idea...

And it is also subject to restrictions. There are indeed 200l barrels. However, from a certain quantity onward, appropriate training is also required. Rightly so, by the way. Nobody really needs 400l of oil on the road due to poor securing.

If you had asked not here, but at the regulars' table, I would advise you to get an IBC tank and a drill pump. Then you load the IBC onto a trailer and drive to the unloading point and pump it back into your tank.

What should be particularly noted:

- If possible, do not drive, or only very carefully drive with a half-filled tank. Because it starts to rock.
- Do not pump out the sediment from the tank. Suspended solids and residues have collected there over the years.
- Secure the container well on the loading surface.

But you asked here and not at the regulars' table, so I answer as follows: Let the old crap be pumped out and be happy if you don't have to pay for the "disposal". Organizing the transport and disposing of the oily mess afterwards costs more nerves and time than 400 liters of heating oil cost...