Backyard Aquaponics
A place to discuss aquaponics

BYAPers,

Anyone here using automatic air vent valves to help avoid airlocks in the tubes? I don't think I've seen anyone mention them before -- just some DIY manual air release valves. Perhaps these would be particularly useful for those using inverted U siphons... Here's an example of one on ebay for $8.50 USD:

WATTS FV-4a REGULATOR HYDRONIC AUTOMATIC AIR BLEEDER

Note: I don't know the seller or anything about them, but only use them as an example for those seeking further info.



WATTS FV-4 Automatica Vent Valves
http://www.watts.com/pages/_products_details.asp?pid=664
http://media.wattswater.com/ES-FV-4M1.pdf

Spec-sheet on this model says minimum working pressure: 1.45psi (10 kPa).

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Sam

Cheap but I cant think of any situation in aquaponics where you would need them

I have no plans to use them right now, but I'd worry about eventual airlock, or perhaps at least degraded performance by air build up inside the tubes, when using a "no holes overflow" siphon that some like. I've seen examples of how folks try to bleed off the air buildup with various tricks like this:



TCLynx started a thread with many examples of "no holes overflow" siphons here: no holes overflows.

Perhaps that would be a good place for an automatic air vent valve if they are reliable enough.

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Sam

On that drawing theres no way that an auto air vent would work

Indeed, if it opened at all, it would just suck in air, and break the syphon.

But wouldn't something like this always have a check valve sort of thing to prevent air from entering since its primary purpose is to purge air that may be in a hydronic heating or cooling system?

TCLynx had several inverted U water-bridge siphons in use at one time. I'm still re-reading that thread mentioned above so perhaps I'll get to the final results and conclusions from her implementations soon. Here's an example of a where a check valve is used with attached air tube to manually suck out the air.

[click pic for thread]


I believe these were regular aquarium air pump check valves being repurposed.

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Sam

Yes it can remove air, but must be attached to a vacuum pump of some sort (or your mouth) to do so, so it is hardly automatic. If you open the valve with no suction on the tube, then the inverted U tube will fill with air.

Right, those automatic air bleeders work in pressurized heating systems... pressure forces the air out until the water level raises the float and closes the valve. If more air enters the system it collects in the bleeder until the float drops and valve opens again.

Yes, functionally, pressure on the inside= vacuum on the outside. They are never going to work in the situation pictured in Sam's post a few days ago.

Yeah, I could see where the pressure in a tube like that is less than the minimum working pressure this particular valve requires. But with a one-way air valve preventing air from entering, would something like this just need slightly more pressure than atmospheric pressure on the outside of the tubes to work?

Hmmm... [quick study of siphon theory] ... nope... okay, so the pressure inside the tube of a siphon is negative. However, water pushing air in a tube compresses the air -- so higher air pressure in that case. I suppose if the water is pulling the air rather than pushing it, that would not be the case. Apparently after more than 3 millennia of siphon use, we still don't fully understand them. Even the most recent scientific research on siphons at best produces yet another non-conclusive theory. But siphon theory is better left for another topic.

I'm convinced that automatic valves that just work on positive pressure won't be the magic bullet in a siphon.

To paraphrase a famous US Supreme Court decision 60 years ago... We may not be able to fully explain a siphon, but we all know one when we see one. And obviously as long as one works, it matters not one twit to plant nor fish, why it works... just that it works and works reliably.
Thanks for the interesting discourse everyone!

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Sam

Phew at last

Jajaja.... in Spanish they say I'm "más terco que una mula" (more stubborn than a mule) and it's probably true, but I do listen to reason!

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Sam