With the older style gravity feed there is an input hole for water and a vent to allow air to escape. These new ones just have the air vent. If u use the vent to fill in water how does the air escape? Could this cause a pressure problem or do u just fill the water slow enough to allow air to come back up the same tube
Filling the fresh water tank via the vent/fill hole is similar to filling a car with gas. It's not a tight seal, so the air comes back up the pipe. It overflows when you fill it up.