  A Bethe-Peierls treatment to dilution in frustrated magnets and spin liquids
is given. A spin glass phase is present at low temperatures and close to the
percolation point as soon as frustration takes a finite value in the dilute
magnet model; the spin glass phase is reentrant inside the ferromagnetic phase.
An extension of the model is given, in which the spin glass / ferromagnet phase
boundary is shown not to reenter inside the ferromagnetic phase asymptotically
close to the tricritical point whereas it has a turning point at lower
temperatures. We conjecture similar phase diagrams to exist in finite
dimensional models not constraint by a Nishimori's line. We increase
frustration to study the effect of dilution in a spin liquid state. This
provides a ``minimal'' ordering by disorder from an Ising paramagnet to an
Ising spin glass.
