The steam does not come out of the vent, because it is water. It is only maintained as a gas at 100 degrees, or more depending on the water pressure in the system. When it tends to rise, it cools, and becomes water again. But as this contraction produces a reduction in pressure, more steam is produced, because the state passage is easier.
And also, when steam is produced where the fire is, a vacuum is made, and it heats faster than if it had water. It is like a vicious circle.
The pressure of the water weight with the hot water tank is the point. The higher the pressure, the lower the temperature necessary to reach the boiling point. In short, less temperature, more steam.
Thank you very much for your attention.
So that I close everything ... then if I put it between the water heater and hot water tank, a non-return valve would solve everything ... well, no pressure would come from the water heater to the water heater ...
It would be like this?
Not so simple. If you get to heat the water with fire and steam is produced, with the pressure you will have a mini Chernobyl at home.
The issue is complex, the escape or relief that can be put, will randomly have steam or water. Y