Valve/Material for Siphoning Air & Blocking Water

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
Sign up Log in
5 replies · 3K views
SAG93
Messages
1
Reaction score
0
Hello,
I wonder if anyone knows of a valve or material that would allow air to pass both ways but prevent water to pass one way.
It will be on the end of a tube used for siphoning so that air can be blown in and suctioned out but if water is collected it is diverted away from the end of the tube by the valve/material into a separate bucket. There would need to be an arm off the tube at the point of the valve/material to redirect the liquid down.
 
Engineering news on Phys.org
Welcome to PF.
There are valves for anything you might need. https://en.wikipedia.org/wiki/List_of_valves
Automatic valves are commonly used to drain water from the bottom of a compressed air system, or to vent air from a high point in an otherwise closed pressurised water system.

Consider a ball that floats against a seat and so blocks the upward flow of water only.
Also consider keeping the outlet of the siphon below the surface of an outlet reservoir.

You have not identified at which end of your system the valve can be located. Is the internal pressure there above or below atmospheric pressure? Maybe a diagram would help. Drag and drop it into your post.
 
The amazing TEMISH sheet allows air to pass through, but not water. Stick it on a cup containing water, and water will not spill even if you turn the cup upside down.
 
  • Like
Likes   Reactions: anorlunda
@Elsa Black. Welcome to PF.
Thanks for the suggestion.

TEMISH™ is a dust and waterproof Fluoroplastic Porous Film that will allow air to pass.
https://www.nitto.com/au/en/products/group/temish/
It appears to be available as small stick on filters that protect high technology from the environment.
But does it allow water vapour to pass with the other gasses?

Gore-Tex is a similar PTFE material that can repel liquid water while allowing water vapor to pass.
https://en.wikipedia.org/wiki/Gore-Tex

The problem with these fabrics is that they can rapidly be blocked by material such as algae.
Unlike mechanical valves, they can only support a low rate of flow.
 
Elsa Black said:
The amazing TEMISH sheet allows air to pass through, but not water. Stick it on a cup containing water, and water will not spill even if you turn the cup upside down.

That does sound unique. But it doesn't say how fast the air passes through. The OP has a siphon entrained with an air bubble. Let's say that the air bubble builds up in the pipe at rate of 1 cm3 per minute. The pressure difference inside the pipe and out is slight. Roughly how much surface area of TEMISH would be needed to do that job?