How to disable WAL?

How can I disable WAL?

As many benefits it may have in speed and stability, I need to disable
it in order to restore a database. My 10 Gb database, for some reason,
won't restore on a 40 GB disk because pg_xlog blows all the available
space, after which postmaster craches...

Is there a configuration file switch that I can use?

It totally excapes me why that amount of disk space is required - the
database is about 10 GB in postgres. It dumps to roughly 6 GB. But it
then 25 GB of free space is not enough to restore it. What's going on?

Cheers.

Gordan