New tanks on 170d11fa, when is a pump needed?

[Peterdenmark]

Hi

I put some extra tanks on the the old feurwehr truck in Marokko. The lowest point on the new tanks are some 40-50 cm below the old tanks (which are placed very high). There is no electric fuel pump at the moment.

Do I need an electric pump on the new tanks?

Also there are three fuel lines from the engine to the fuel tank. One is obviously the intake and then the two others are both return? Or?

The new tanks are only prepared for two fuel lines, can I combine two of the fuel lines to one or is there a very good reason that they are separete?

Best reagards Peter