Float valve not closing every time

[redboat219]

I've not got one of these vacuum breaks, but I recall Ron saying they're not designed to have a perfect seal, else they wouldn't relax once the device was above the water. The idea is that any gap is small enough that the pump can empty the tank faster than any leakage past the vacuum break.

So the principle is the same to using a small diameter tube at the end of the snorkel. It lets air in and out easily but restricts water flow thereby letting the pump to partially empty the ballast tank just enough to to impart positive bouyancy to the sub to let the tip of the snorkel break the air-water interface.

https://youtu.be/RqnxuMlmhkA

[JohnDora]

UPDATE 24th June

The float - a ball - seems sometime to stick on the bottom of the cylinder / drum, having checked looking through the holes with my phone’s light. Blowing air with an air duster tube inserted in one of the holes releases it and it spins like a pea in a whistle. Wonder why and what is ‘holding’ it down?

John

[JohnDora]

So if a small diameter tube is used, doesn’t this restrict the flow so making it slow to dive? No, as air is being expelled… All down to physics (ye canny change the laws of physics!).

[redboat219]

UPDATE 24th June

The float - a ball - seems sometime to stick on the bottom of the cylinder / drum, having checked looking through the holes with my phone’s light. Blowing air with an air duster tube inserted in one of the holes releases it and it spins like a pea in a whistle. Wonder why and what is ‘holding’ it down?

John

It's called gravity. lol

[Subculture]

Does it stick to the base when in the water? As I've never had one of these to muck about with, I don't know exactly the materials used, so I just give a best guess on how I might approach it in lieu of details from the horses mouth so to speak. I would estimate the ball used in the snorkel is made from a (very slightly) buoyant plastic like polypropylene. When out of the water it will fall to the base of the container as required to enable the tank to fully evacuate.