  We consider the standard first passage percolation model in the rescaled
graph $\mathbb{Z}^d/n$ for $d\geq 2$, and a domain $\Omega$ of boundary
$\Gamma$ in $\mathbb{R}^d$. Let $\Gamma^1$ and $\Gamma^2$ be two disjoint open
subsets of $\Gamma$, representing the parts of $\Gamma$ through which some
water can enter and escape from $\Omega$. We investigate the asymptotic
behaviour of the flow $\phi_n$ through a discrete version $\Omega_n$ of
$\Omega$ between the corresponding discrete sets $\Gamma^1_n$ and $\Gamma^2_n$.
We prove that under some conditions on the regularity of the domain and on the
law of the capacity of the edges, the lower large deviations of $\phi_n/
n^{d-1}$ below a certain constant are of surface order.
