11. (5 points) To create a green school, the Science Club students designed a pond to recycle the vegetable washing water from the school canteen to water the flowers. It is required that the inlet pipe alone can fill the pond in 3 hours, and the outlet pipe alone can drain a full pond in 4 hours. After the pond was built, it was found that the pond was leaking. At this time, if the inlet and outlet pipes are opened simultaneously, it takes 14 hours to fill the pond. Then, when the pond is full, and the inlet and outlet pipes are closed, it will take $\qquad$ hours for the pond to leak out completely.
【Solution】Solution: The efficiency of the inlet pipe: $\frac{1}{3}$, the efficiency of the outlet pipe: $\frac{1}{4}$,  
the combined efficiency of the inlet pipe, outlet pipe, and the leak: $\frac{1}{14}$, if there is no leak, the efficiency of opening the inlet and outlet pipes simultaneously: $\frac{1}{3}-\frac{1}{4}$; the efficiency of the leak:
$$
\begin{aligned}
& \left(\frac{1}{3}-\frac{1}{4}\right)-\frac{1}{14} \\
= & \frac{1}{12}-\frac{1}{14}, \\
= & \frac{1}{84} ;
\end{aligned}
$$

The time required to drain the entire pool:
$$
1 \div \frac{1}{84}=84 \text { (hours); }
$$

Answer: It will take 84 hours for the entire pool to drain.
Therefore, the answer is: 84.