Harry K wrote:
On Feb 5, 10:38 pm, "Bob F" wrote:
Harry K wrote:
But really, when the flush valve opens, the pressure is not what
operates, it is the velocity of the water. The pressure is what gets
you the velocity. Thus it doesn't matter what the pressure in the
mains is, your tank height is all that counts. Even the "pressure
assists" operate the same way.

You don't have "pressure" unless the water is confined in something.

The water is confined by the orifaces in the toilet. Otherwise, it
would drain the tank a lot faster. Try flushing a tank removed from
the toilet.

If there were no pressure, they wouldn't need a gasket between the
tank and the base.

God! We are talking about how a _flush_ works, not what the pressure
or anything else is in the tank prior to the flush. Any container
will have pressure when filled with _anything_.

Again: Once the water exits those "orifaces" it has no pressure, only
velocity because it is no longer confined.

But to get through those orifaces with velocity, it needs pressure.