I've tried to manually put labels (1-2-3-4) on the arrows tip in the center of the connection lines but it seems not working good..How can i fix this?

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning,intersections,shapes.geometric,decorations.pathmorphing,decorations.pathreplacing,decorations.shapes,decorations.markings,patterns,calc,fit,arrows,backgrounds,matrix}
\begin{document}
\begin{tikzpicture}[auto]
\tikzset{deco/.style={decoration={markings, mark=at position #1 with {\arrow{>} }},postaction={decorate}}}
\tikzset{trape/.style={trapezium,draw,shape border rotate=90,minimum width=2cm}}
\tikzset{box/.style={rectangle,draw,minimum height=1cm,minimum width=2.5cm}}
\tikzset{cerchi/.style={circle,draw,minimum size=1cm}}
\matrix [row sep={1.5cm}]
{
&[2cm] \node [box] (genera) {}; &[2cm] &[1cm] \\
\node [cerchi] (pompa) {}; & & \node [trape] (turbina) {}; & \node [cerchi] (ultiliz) {}; \\
& \node [cerchi] (condensa) {}; & & \\
};
\begin{scope}[>=triangle 60]
\draw [deco=0.6] (genera) -| node[pos=0.6]{2} (turbina.top right corner);
\draw [deco=0.6] (turbina.bottom left corner) |- node[above=1mm,pos=0.71]{3} (condensa);
\draw [deco=0.4] (condensa) -| node[above=1mm,pos=0.31]{4} (pompa);
\draw [deco=0.6] (pompa) |- node[below=1mm,pos=0.63]{1} (genera);
\end{scope}
\draw [->,>=latex,very thick, shorten >=4 pt,shorten <=4pt] (pompa.south)--(pompa.north);
\node [coordinate] (B) at ($ (condensa.center)!.6!(condensa.west) $) {};
\node [coordinate] (C) at ($ (condensa.center)!.6!(condensa.east) $) {};
\node [coordinate] (A) at ($ (B)+(0,-1.5cm)$) {};
\node [coordinate] (D) at ($ (C)+(0,-1.5cm)$) {};
\draw (A)--(B);
\draw[decorate,decoration={zigzag,amplitude=3pt,segment length=8pt}] (B)--(C);
\draw (C)--(D);
\end{tikzpicture}
\end{document}

