Vacuum Relief Valve

The vacuum relief valve is used to let air into the main line so as to stop siphoning.

Advantages

• Stops siphoning
• Low cost

Disadvantages

• If the entire main line is down hill from the pond then the whole line will still empty out.

Things to consider

You may need to install multiple valves to stop the siphoning. If the main line has high and low points then the valve can be put in the main line at each high point. It also allows air into the line to prevent the line collapsing under vacuum.