Did the closed to open cooling swap - but?

Hi all,
Because both my radiator and pressure tank and cap had issues, I decided to change out my cooling system for open system. I am however puzzled by one step and can';t seem to find the info.
The coolant recovery bottle hooks up with 1 hose from the overflow of the filler neck of the new radiator.
I can see how coolant under certain conditions can be forced out of the neck and into the tank, but I don't see how it gets from the tank back into the cooling system.
Being that the radiator cap seals the radiator and it takes pressure greater than 13 psi to open it, it has to act as a one way value......right?

Thanks
Don

Radiator caps for modern, open systems have two valves built into them. As the radiator coolant cools, it contracts, causing a vacuum, which sucks the coolant out of the recovery bottle back into the radiator. With the radiator completely filled when cold, there is not any air space left to deal with the coolant when it naturally expands during normal operation. The pressure valve in the radiator cap lets the expanding coolant flow into the coolant bottle. You should observe that the coolant level rises in the "bottle" as the engine warms, then after the engine is shut down and begins to cool, the level of coolant should drop.

I would get a fresh (16 LB) cap. They are very cheep and easy to install. At least get a fresh cap anyway, I have found a 24 LB cap off of some Ford that fits. But I do run the increase risk of blowing a pump seal sooner at that PSI.

I am running a 13lb, which I think is the spec's for a cap in 92.

Thank you
Don