How do air vent caps work?

In this week’s edition of Ask Caleffi, Cody Mack (Technical Support) will give a brief demonstration on when to use certain air vent caps.

[randy_constan]

I've an unusual need in an air valve and I don't know the proper word to describe it. I want to install it at the top of a swimming pool filter, and its purpose would be to allow air to escape, but close as soon as the water reached it. The need is due to the fact that the pump inevitably draws some air, which then accumulates at the top portion of the pool filter. That condition prevents as much as 1/2 of the inner filter cartridge from being properly used. The filter has a manual valve at the top for letting out air when a new filter cartridge is installed, but its intended to be manually closed once water starts pushing out. If I were to build what I'm looking for, it would simply be a vertical tube, narrowed at the top, with a heavy hollow ball inside, which would sink to the bottom as long as air was flowing, but float to the top and block exit once water pushed into the tube. Does such a valve exist? Would it be one of the ones you are describing? Thanks for any assist!

[homediddy]

Is the hygroscopic air vent food safe? Im in the early stages of building a portable drinking water storage tank that will need to be able to be vented but not let any water out regardless of the orientation of the tank.

[drizzydre]

I just took my heater cover off and only see a black rubber piece like the one you had on table in front of you. Should I put it back on? Because it’s been off this whole time and I didn’t know

[Jorge.O]

So it has to be opened ? By haft turn ? Not complety close. ?

So of theres air inside the pipes i will hear the horrible noise inside ?

[shelby]

my cap is red plastic and its not solid on top it has two tiny holes / slots openings on each side

[shelby]

hi i have a water boiler boiler heating system that is leaking water at the top of the air vent part..the red cap is broken is water suppose to be coming out when cap is off or broken? th

[danila.motovilov]

Было бы хорошо если бы было на русском, я английского не знаю, поэтому ничего не понимаю, хотя с удовольствием продаю ваш продукт;) Действительно качество на высоте. Аналогов нет!

[Jerseyhighlander]

Is there ever a point when you do want water dripping out of your air vent cap? Don't think I've ever been there.