Siphon Overflow – Pond

If you want to lower the level of your 1+ acre pond and you want to have an overflow that can lower your water level very fast, think of the siphon principle.
With a siphon the flow is about 5-8 liter (about 2 gallon) PER SECOND.

When we bought our current house, it came with a pond. A two acre pond.
Everything looked fine and this was the overflow at that moment. The 3 inch pipe was basically going to nowhere and there was a lot of erosion.

When cleaning the pond, it looked like it the water level was about 3 feet to high. First I started pumping out the water, but that took forever.
Because I already wanted to change the overflow, why not create an overflow that can also be used to lower the water level. How? With the siphon principle.

Here is my current setup of the overflow:

Components used:
1 = Inlet. I have it under a hook of 45 degree so it won’t get all the dirt from the bottom of the pond.
2 = Outlet. To have less corrosion of the other pond and bank, I used a 22 degree as outlet.
3 = Valve.
4 = Valve and plug (In my case it is a T with a plug that I can open and close to fill the PVC pipe for a manual start.)
5 = Valve for air
The PVC pipe is 4 inch. The air pipe (5) is 2 inch.
The PVC pip at the top is NOT horizontal. the part towards the outlet is slightly lower than at the valve 4. This is to fill the whole pipe to start the siphon principle manually.

Manually start the siphon

I wanted to lower my pond with at least 3 feet. A pump would take a couple of weeks to have it at the right level. With the siphon it took about 36 hours.
Valve 3 should be closed and is used when you want to start the siphon principle manually. Close valve 5 and you can put water in 4 until the water is not streaming to the outlet, but to the inlet.
Now you close 4 and open 3. After about 3 seconds, the water will flow very very fast!
The outlet should be lower than the inlet. In my case the pipe to the outlet is twice as long as the inlet pipe.

Normal overflow

To have the overflow working normally, open 3 and 5 and make sure 4 is closed.
Overflow without siphon principle:

Siphon Overflow normal operation

Overflow kick in Sip

When the pond water is higher than the pvc pipe, the siphon principle kicks in. In my case that means with a 4 inch PVC pipe, the 2 acre pond will be lowered by 1 inch an hour.

Siphon principle is working:

Siphon Overflow Pond is working

Automatically stopping the siphon overflow

When the siphon is working, the water level of the pond will be lowered until pipe 5 will gasp air.
Make sure valve 5 is open. If it is not open, your pond water level will be lowered until no water can be sucked up.
In the next video you see I am stopping it manually by raising the air pipe. As you can see, the forces are very big.
Stopping the overflow siphon:

Siphon Overflow stops automatically
You can hear the overflow stopping.

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