Does anyone know...

[Ya Ya]

When pulling back on syringe to see if registered the contents flow to the opposite end and now the air space is up by the plunger. Why is this happening?

 

[wezface]

You're creating suction in the barrel, which affects the contents therein.

 

[szuko000]

Right its a typical vacuum equalizing situation. Generally speaking the vacuum really wants to be filled so it starts from the back and goes up if you will. I think its because the vacuum is the entire length of the system and as such it must fill from the back to the top as the back still experiences a vacuum when the water removes the vacuum from the front as it fills up thus getting pulled all the way to the back.

Its kind of hard to explain but just think of it like this it makes more sense to remove the vacuum from back to front if you are filling to from the front as the vacuum pulls that front amount to the back instantly.

 

[Ya Ya]

Thanks