  $\pi^+\pi^-$ transitions of heavy quarkonia, especially the $
\Upsilon(3S)\to\Upsilon(1S)\pi^+\pi^-$ decay process, are revisited. In the
framework of the Chiral Unitary Theory (ChUT), the $S$ wave $\pi\pi$ final
state interaction (FSI) is included. It is found that when an additional
intermediate state with $J^P=1^+$ and I=1 is introduced, not only the $ \pi\pi$
invariant mass spectrum and the $cos\theta_\pi^*$ distribution in the
$\Upsilon(3S)\to\Upsilon(1S)\pi^+\pi^-$ process can simultaneously be
well-explained, but also a consistent description for other bottomonia $
\pi^+\pi^-$ transitions can be obtained. As a consequence, the mass and the
width of the intermediate state are predicted. From the quark content analysis,
this state should be a $b\bar bq\bar q$ state.
