  We consider the possibility of charged stable Kaluza-Klein leptons in
orbifold models in which all the Standard Model fields propagate (UED models).
At tree level the masses of the 1st mode states are nearly identical and
kinematics can prevent the decays of the 1st mode charged leptons. Perturbative
and non-perturbative affects alter this picture and allow for a range of
possibilities. For single extra dimensional UED-type models with stable
Kaluza-Klein charged leptons we calculate their production from the
all-particle incident flux of cosmic rays and find that null results in direct
searches for anomalously heavy water suggest a lower bound on the
compactification scale: 1/R > 290 GeV.
