Siphoning 101 Question

[Beltzington]

I'm in the middle of repairing my well pump PVC plumbing which for the first time in 10-years froze and cracked. The well is rarely used so I am not in a hurry which has left me with time to over engineer the repair. I have been siphoning liquid from tanks and irrigation ditches since I was 10-years old but for some reason I can't wrap my mind around this question.

Can you siphon water out of the well pump drop pipe? My initial thought is you could not generate enough vacuum but gravity is a wonderful thing so now I am curious what factors limit the process.

 

[4570Man]

Only if you’ve got a point lower than the bottom of the pipe. I’ve heard there’s is a limit on the depth a siphon will work but I’ve never reached that point. You can shove a smaller pipe down it with a cap on it which would force most of the water out the top. The mythbusters recovered a sunken boat by forcing enough ping pong balls in it.

 

[/pine]

I'm in the middle of repairing my well pump PVC plumbing which for the first time in 10-years froze and cracked. The well is rarely used so I am not in a hurry which has left me with time to over engineer the repair. I have been siphoning liquid from tanks and irrigation ditches since I was 10-years old but for some reason I can't wrap my mind around this question.

Can you siphon water out of the well pump drop pipe? My initial thought is you could not generate enough vacuum but gravity is a wonderful thing so now I am curious what factors limit the process.

AFAIK outside of a vacuum water will flow down hill...if the outflow is below (in elevation) the input it should flow...

 

[RNeumann]

Siphon or pump? If it’s siphon it’s as stated so I’m not sure how u r going to get the drop.
If it’s pumping from above you are relying on the atmospheric pressure to create a “vacuum” that will allow water to be “sucked” out. With the proper pump and tight seals you can pump, in theory, about 28’ below the pump to the top of the water level- in reality it’s about 25’.

So if you have a 100’ well and the pipe goes top to bottom you could attach the proper pump at the top of the pipe (ground level) and pump out about 1/4 of the water- about 25’ below grade.

 

[4570Man]

You could run a tube to the bottom of the pipe and seal around the tube and the pipe. Then pressurize the pipe with an air compressor and it would force water out the tube. All of this is assuming it has to be drained.

 

[RalphVa]

You can pull water up with a pump. Technical limit is the feet of water expressed as the difference between atmospheric pressure and the fluid vapor pressure. Get more suction or footage than that, and it'll boil into the pump, and the pump will stop pumping and further overheat. In practical terms, you have to have a footer valve (just a check valve, more or less) and then prime the suction pipe with the same cool water you're sucking up. Most successful pumps for doing this are piston pumps. They might do it without priming.

For pure siphoning, you have to be going downhill from where you're sucking from.

Ralph

 

[bcp]

The height limit of a siphon | Scientific Reports

Bruce

 

[airbiscuit]

My only experience has been with siphoning gas.

Step 1 Insert hose into the vessel with fuel

Step 2 Suck on the hose until you have a mouth of gas.

Step 3 Stick the hose into the empty gas can

 

[Beltzington]

The height limit of a siphon | Scientific Reports

Bruce

Thanks Bruce, an interesting read. Clearly Australians think about more than how many prawns to be on the Barbie my mental hiccup was much simpler, I wasn't considering the check valve on the supply side of the system, no air in no water out the spout. Appreciate all your comments.

 

[/pine]

...no air in no water out...

That's why a siphon will not work in a vacuum...