Recyclers are all different, even those blown in the same pattern are nearly impossible to precisely match to have any kind of universal water levels. Some scientific rigs will have an indication for water level but it's very rare to see that. Ultimately it's up to the user and the use case. Because of all that, it really varies widely between the many different types of recyclers, devices and people.
(Sneaky Pete offers a similar-ish style to the distilledglass one above, which I have seen simply not function with a vape attached, because it needs more water but then it can't handle more water. Having a honeycomb should mean an airy percolation chamber, a slotted inline isn't going to behave with the same bubble stacking, it's not meant to be an airy percolation in that oil rig).
With the pic above (
@Ramahs did you reupload? Looks like
www.imgbb.com will be my go-to now that Tinypic is no more)
Here's my most relevant pic (testing imgbb), not particularly cheap, and the quality is debatable, but a great spot for a quick spot of insta clouds.
As with all recyclers, the water balance is a little picky. This one manages to function with the water just covering the perc, but it works better with a bit more, and it starts to splash the mouthpiece about halfway up (although the perc function is still firing nicely , it needs a chamber between the neck and body to avoid splashes).
Adding lots of water above the perc of a recycler just adds a nice bit of chug. Once all the water is displaced, the thing should fire up and it won't need much to keep it moving. Ideally with a lot of water it will just keep cycling despite drag speed, and the mouthpiece will stay dry.
It'd be a design flaw if the water needed to be filled into the upline tube, that might happen as the water shifts from the stemless entry, but as long as you're not getting a drink and are happy with the chug, then it's fine - enjoy that super smooth inhalation!
If that piece had a gridded inline, you would find it'd stack MUCH more and require less water to cycle through, but it also changes the style and signiture of a hit.
When the water level is wrong for the use case, the piece acts like a simple rig with a splash guard. You should feel the constant motion with a recycler, if the water isn't flowing right, it means the toke speed is chopping and changing. A good design should offer a smooth and consistent pull once the intitial chug is dealt with.
Here's one just managing to function with an airy percolation chamber and a reasonably open airflow vape (would better perform with the PFE). You can see when the vape is removed and the chamber is cleared how the water is supposed to move, the levels are fine without a vape, but not great with it. This is why it's hard to match a recycler to a vape, they're all different and you often can get a drink when removing the vape to clear the rig
... Happy Friday
And with a small discount on Ebay. Got it in 2 weeks to the US. 
, I now have 14 to 18mm dropdowns
)