  We present a detailed NQR, NMR and $\mu $SR study of a magnetic phase
obtained during a topotactic chemical reaction of YBa$_{2}$Cu$_{3}$O$_{6.5}$
high- temperature superconductor with low-pressure water vapor. Our studies
give straightforward evidence that the ''empty'' Cu(1) chains play the role of
an easy water insertion channel. It is shown that the NQR spectrum of the
starting material transforms progressively under insertion of water, and
completely disappears when one H$_{2}$O molecule is inserted per unit cell.
Similarly, a Cu ZFNMR signal characteristic of this water inserted material
appears and grows with increasing water content, which indicates that the
products of the reaction are non-superconducting antiferromagnetic phases in
which the bilayers are ordered. These antiferromagnetic phases are felt by
proton NMR which reveals two sites with static internal fields of 150 and about
15 Gauss respectively. Two muon sites are also evidenced with similar local
fields which vanish at $T\approx 400$ K. This indicates that the magnetic
phases have similar N\'{e}el temperatures as the other bilayer undoped
compounds. An analysis of the internal fields on different sites of the
structure suggests that they can be all assigned to a single magnetic phase at
large water content in which the Cu(1) electron spins order with those of the
Cu(2). It appears that even samples packed in Stycast epoxy resin heated
moderately at a temperature (200$^{0}$C) undergo a reaction with epoxy
decomposition products which yield the formation of the same final compound. It
is then quite clear that such effects should be considered quite seriously and
avoided in experiments attempting to resolve tiny effects in such materials, as
those performed in some recent neutron scattering experiments.
