Pond Boss Forums INTRO New Forum Member Introduction Need help with manhole siphon to pond

I have a spring feed manhole 5' dia by 7' deep,it puts out about 40 gal a minute,have a 3"pipe to my pond 100'away. The 3" drain pipe is 12"from the top of the manhole and drains to the pond,approx 30 gallons per minute with 12'fall.when i pump the manhole down to 5'it puts out about 100 gal a minute,the bottom of the pond is approx 5'below the manhole bottom.any ideas for a siphon,so i would not need a pump?
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ZRT if your pond is lower than the spring once you start the water flowing in the pipe it should continue to flow once you disconnect the pump, or am I missing something in your description.

I have 2 pipes running 300ft, from above a waterfall down to the pond, once I start the flow with a pump it's disconnected and the siphon does the rest.
Both pipes are 2 inch gray pvc and total supply is 110 GPM.

A manhole? Is the manhole a drain for the spring? The only manholes we have are in sewer systems.

Thanks for your input,yes the manhole i installed is right on top of spring,that puts out approx 100 gpm at the bottom of the 7'deep manhole with a pump.Without the pump the water rises approx 6'in the manhole and starts to drain to the pond,but only produces 40 gpm.I am trying to siphon at 6'down in the manhole and get more water flow,can i regulate the gpm with a valve in 3"pipe so i don't suck the manhole dry and loose my suction or would it better to use the 3"pipe for a raceway and slide a 1 1/2 or 2" pipe in it all the way from the manhole thru the 3" pipe bottom to the bottom of the pond.

There's a lot I don't know about springs. There's also a lot I don't know about pumps.

However, the pumps that I have used had a shut off switch when the water level dropped.On the spring, could you eliminate the manhole and just go down to the spring and let it run directly to the pond? Or, if it is below pond level, could you run it into a catch basin at 100 gpm and then pump from there?

40 gpm puts out 2.13 acre ft. of water in a 24 hour period. Figure on one inch of water over one acre being 27,000 gallons.

You could put a valve at the bottom end of the line near the pond to control water flow, I have a gate valve on one of my lines to regulate it.
http://www.amazon.com/Valterra-Gate-Valve-SxS-6301/dp/B000PR50YY

Once you start the flow with the pump you could disconnect it and put a pipe extension on reaching down 6 ft, but the connection needs to be air tight so you don't loose suction, I've found that the rubber pipe connectors with clamps work well which allows you to disconnect the extension if you need to.
http://www.fernco.com/

You could also have the pump connected to the bottom of the extension but when the pump is off it restricts a lot of the flow, maybe try it first with the pump connected and see if the flow is sufficient when turned off.

adirondack,i think i will extend the 3" to the bottom of the pond and also extend the 3" in the manhole down to 1' from the bottom of the manhole,which end do you think i should install the pump on? the pond end or the manhole end which would be approx 3'higher than the pond pipe end to get the siphon working.also i will install a 3" gate valve where the 3" enters the pond,thanks Lee

ZRT you should keep the outlet above the pond surface so it splashes into the pond or on some rocks so that it helps aerate the water.
Is your pump a surface pump or submersible pump?, I prefer a submersible pump which you could hook up to your pipe in the spring hole and after the flow starts turn off the power to the pump and measure the flow rate, if the flow is less than you want disconnect the submersible pump while keeping the pipe submerged so you don't lose suction and see if that flow rate is acceptable.
Since your using a 3" pipe I assume you have to reduce the size of the pipe to the pump, let me know what kind and size pump you have, from your description it sounds like you have a surface pump.

adirondack,the outlet has to go to the bottom of the pond so it will be below the intake elevation or it will not siphon,i have several submersible pumps 1 1/4 and 2" i will have to increase it for the 3" pipe i think you are right water should flow thru the pump after disconnecting power,i could install a tee with a valve next to the intake pump if needed and open it from above without losing suction,i hope it works,pond is 250 miles north me it on my hunting land,i will try to get it working next week,Thanks Lee

Lee, putting a T valve above the submersible pump would work great, but you have me confused .
You mentioned in your first post that you had a 12' fall from the spring hole to the pond, but you said that you have to put the pipe outlet to the bottom of the pond to get it below the spring. If the surface of the water in the spring hole is not above the surface of the pond a siphon will not work.
If I've misunderstood let me know, my pond is also not where I live, it's 95 miles north.

Here's my first 2" siphon pipe, starting it up during a warm spell in the winter, it has a 10 ft. vertical drop to the pond, but it's 300 ft. to the pond.

I am confused also. By putting the siphon outlet at the bottom of the pond, I would think that the water pressure exerted by the pond water column would severely limit any siphon action.

I am sorry guys its only 12 inches fall to the pond not 12 foot,thats why i have to extend the 3" pipe to the bottom of the pond so its below the intake.instar,i have thought about your comment in the past,maybe the pressure at the bottom of the pond will restrict the siphon action and not let it flow,Thanks Lee

Lee if the spring level is 12" above the pond you should be able to get a siphon flow but doesn't allow you to draw down the spring much so you would only get as much water as the spring keeps that level above pond level, so a valve would be required to regulate the flow so it doesn't lose suction.

Another option would be to use a smaller continuous rated fountain pump which would not use alot of power but give you a steady flow.
Last winter I used a fountain pump in a bucket in the stream to keep water flowing to the pond. The stream flows about a 100ft from the pond but by then it's 9 ft. below the pond so I insulated the pipe and it ran all winter at about 10 GPM.