Picking up on the discussion "Air build-up in a siphon system"

[brad miley]

TL;DR Summary

This post is in response to a thread started by Grizzster on May 20th, 2015, titled "How can I get rid of air buildup in a siphon system"? The last post was August 4th, 2022, and is now "not open for further replies."

In 2018 after having suffered several 4- and 5-day power outages, I started to develop a siphon system that I hoped would automatically and continuously remove ground water from our basement's sump basin. (Siphon specs. at our house: head 58", apex height above source water 80" (apex is directly above source water), 1" I.D. tubing runs 300' beyond the apex with a relatively consistent drop, and the output end sits in a bucket that overflows.

I started by making a simple intake end float valve to regulate the siphon's uptake so as to match the rate at which water entered the basin. The higher the water in the basin, the more the valve opens; the lower the water, the more it closes. This worked well for 1 to 3 days and then a bubble would form at the apex and stop the siphon. I made sure there were no leaks, but it continued to build gas. Sound familiar?

It was a short time later that I found the thread on PF. After a few months, I got an idea. Because the siphon seemed to build gas when the flow was slowest, I thought that if I could completely stop the flow during those low flow periods and let the water rise a few inches then open the valve fully, it may wash any gas build-up downstream. Here is a link to a short video explaining what I came up with: Cycle Siphon.

Note not explained in the video, the tubing remains full of water (primed) when the valve is closed. Once I got the magnets installed and the leverages worked out, it started working and now, as a test, if I remove the magnets, it builds gas again. It's been working for several years and has proven itself to be very dependable. I received a U.S. Patent for this device in August 2023. Number 11,725,377 B1

 

[russ_watters]

Here's that prior thread, for reference:
https://www.physicsforums.com/threads/how-can-i-get-rid-of-air-buildup-in-a-siphon-system.814904/

 

[Averagesupernova]

I watched the YouTube video linked above. I have yet to use a syphon that has a discharge tube large enough to do the job as described above and not empty the downhill run of tube and fill with air when the end submerged in water is stopped off. In a large tube there is not enough surface tension to keep the water in. A slight upturn of the tube might prevent this. @russ_watters what are your thought on this?

 

[brad miley]

I keep the discharge tube's outlet end in the woods submerged in a full 3-gallon bucket and simply let it overflow. I think this is the same effect as an upturn in the tube? I then cover the 3-gallon bucket with a larger 10-gallon bucket for freeze protection. I'm sorry I did not have that information in the video.

 

[Nik_2213]

Tangential, I had a problem with a dribbling 'utility' tap which just needed a '10p' washer, but body was seized, back inaccessible and no local isolator. Have since replaced tap and feed as 'side-quest' for a similar bath-taps issue which needed full house shut-off, but...

So, that pesky tap dribbled, which led to icing problems on its drain. I got a small 'auto-syphon', as used to periodically flush urinals, and fitted it to the base of a tall, narrow plastic bin. The bin would slowly fill to above the auto-syphon's weir, then dump the gallon fill in one 'tranche', preventing icing.
Or, in your case, an air-lock in syphon...

 

[sophiecentaur]

I got a small 'auto-syphon', as used to periodically flush urinals,

Very handy. They use a device like that on the drain of (some?) condensing boilers to keep the outside drain pipe clear of ice by waiting till there's a reasonable amount of condensate to er got rid of.

 

[Nik_2213]

FWIW, have since removed tall kitchen unit to simplify combi-boiler replacement, found that utility tap's 'local isolator'. Accessed, had I known it, via a neat 'porthole + flap' in back of unit. But seized, of course, of course...