Gravity doser question

[c.rob]

I have a 15 gallon container I am going to use for a kalk drip. As the volume reduces in the sealed container will the drip rate change to a vac in the air space above the liquid or less head pressure from the lower volume of kalk ? Or does it stay the same rate throughout ?

 

[fijisrfr]

I believe that if you don't have an air hole it will stop when the liquid goes down. I used the same system for a while & ended up drilling a 1/16th hole in the lid to prevent this from happening.

 

[uncleof6]

Two things happen, and OP nailed them both. A vacuum is not created in the sense that there is no air, (if there was air to beging with) rather the pressure will drop, due to the same volume of air occupying more space, and eventually it will stop, if it even started in the first place. So yeah, you need an air vent. as stated above.

Secondly, as the water level drops, the head height drops, the flow rate through the outlet drops. Chained reaction that equals the drip rate will change, and require adjustment probably.