Alien Invasion - I want my pond back !

[MossRoad]

It depends what is the length of each leg. If the pond side is long relative to downhill side you have to fill both.

Think about that and get back to us.

 

[MossRoad]

Best examples I can find are these:
Downhill side always has to be longer than uphill side because siphons work by gravity and stored potential gravitational energy.

 

[txdon]

Moss, that is interesting - I just thought one side had to be lower not necessary longer, the chain example clarifies that.

 

[the old grind]

Downflow in the lower leg has to suck any air/water from the upper leg faster than the bubbles can rise to the high point to get full flow. The Youtuber had ~35'(?) of fall, smooth pipe, and a total dynamic head <100'.

OP has 45' fall but more than double the run/TDH, more volume to get moving and most likely a slower flow rate due to the latter. (bubbles impede flow 'til discharged) Diameter and pipe walls (smooth vs corrugated, etc) have to be considered. Siphoning is never as simple as just the difference ('fall') between source level and output height.

btw, The OP's bucket reminds of having a jar of fluid at the end of a bleeder hose when bleeding brakes or a hydraulic clutch.

txdon, its the length of each effective leg vs total tube length on either side of the high point that provides the siphoning action. Extra pipe length on either side adds inertia and pipe friction, and they do matter to rate of flow.

 

[dave1949]

It depends. If the downhill side runs out of water before the uphill side fills, you will have nothing but water running back into the pond that made it partway uphill. He may have explained that in the video but listening to those is torture for my hearing.

It doesn't depend. I don't think you understand how siphons work.

It is the water--under the pull of gravity--in the downhill side that will pull the pond side water up the pipe. If the downhill side is not long enough (contains enough water) to pull the pond water over the top of the rise and far enough down the downhill side to have the mass required to continue lifting the pond water, the siphon will fail. It does depend, just like the example you posted later.

 

[MossRoad]

It is the water--under the pull of gravity--in the downhill side that will pull the pond side water up the pipe. If the downhill side is not long enough (contains enough water) to pull the pond water over the top of the rise and far enough down the downhill side to have the mass required to continue lifting the pond water, the siphon will fail. It does depend, just like the example you posted later.

We already talked about filling the downhill side with enough water to compensate for the length of the uphill side.

 

[MossRoad]

Moss, that is interesting - I just thought one side had to be lower not necessary longer, the chain example clarifies that.

Yeah, that's about as good a visual I could find. Pretty much everyone has had a piece of rope, Christmas lights, extension cord, string, etc... in their hands at some time and have seen how if you drape it over something and one side has more than the other, it pulls it down on its own. Siphon works the same way.

The downhill side always has to be longer than the uphill side AND the discharge always has to be lower than the inlet. If its not, it will try to flow the wrong way.

 

[SPYDERLK]

It is the water--under the pull of gravity--in the downhill side that will pull the pond side water up the pipe. If the downhill side is not long enough (contains enough water) to pull the pond water over the top of the rise and far enough down the downhill side to have the mass required to continue lifting the pond water, the siphon will fail. It does depend, just like the example you posted later.

Well described.

We already talked about filling the downhill side with enough water to compensate for the length of the uphill side.

Ignores differing slopes and pipe sizes. In large tubes on a slope the water will not necessarily flow as a slug, but as a stream. Water coming over the hi point with an air bubble ahead can go into this mode thwarting the start of siphon.

Yeah, that's about as good a visual I could find. Pretty much everyone has had a piece of rope, Christmas lights, extension cord, string, etc... in their hands at some time and have seen how if you drape it over something and one side has more than the other, it pulls it down on its own. Siphon works the same way.

The downhill side always has to be longer than the uphill side AND the discharge always has to be lower than the inlet. If its not, it will try to flow the wrong way.

Chains have nothing analogous to air voids or bubbles in fluid. Fluids next to air in a large tube can seek their own level allowing air above the flow. The downhill side does not have to be longer, only to outlet at a lower level.
,,,larry

 

[Redneck in training]

Well described.Fluids next to air in a large tube can seek their own level allowing air above the flow. The downhill side does not have to be longer, only to outlet at a lower level.
,,,larry

The volume of the downhill side has to be the same or preferably greater than the pond side. If it is not the case you have to fill both sides.

 

[MossRoad]

Well described.

Ignores differing slopes and pipe sizes. In large tubes on a slope the water will not necessarily flow as a slug, but as a stream. Water coming over the hi point with an air bubble ahead can go into this mode thwarting the start of siphon.

Chains have nothing analogous to air voids or bubbles in fluid. Fluids next to air in a large tube can seek their own level allowing air above the flow. The downhill side does not have to be longer, only to outlet at a lower level.
,,,larry

So you're saying a 10' long downhill pipe with an outlet 1" below the inlet of a 100' long uphill pipe will work?