A question of "playability'.....

[PlayTheTuba]

For a king, I prefer to hold down the 4th valve and dump the water back through the leadpipe. Better than spinning

A section mate from high-school did that with all of the valves. Definitely more efficient than pulling out slides and dumping the water out.

[LeMark]

I find that I have to do the valves one at a time, unless the water runs places you don't want it

[bloke]

OFTEN, I get things WRONG...

but (if someone's else tuba, whereby - not being yours - you haven't installed a water key there) couldn't (simply) the FOURTH VALVE ONLY be depressed, in order to get the water to run back of the 4th circuit to the mouthpipe and drip out the receiver?

me...??
I would choose (as some here know) 7 or 8 water keys, vs. even one slide pull or one "spin"...

...and yes, you will see a water key on an upper #1 slide on one of my instruments.
(definition of terms: That involves a TILT, which is NOT a "spin". )

...but bloke, won't that affect the sound...??

Absolutely.
The extraordinary list of amazing BENEFITS is nearly infinite.

[LeMark]

Easier said than done when you are working with students. I came up with the "king dump" very early on when I was horrified to see the students spinning tubas in the air

[MikeMason]

One of the practical benefits of rotor horn. 90 + % of my water comes out the 1 water key. So nice

[bloke]

...I was horrified to see the students spinning tubas in the air

Which is why school children need to be playing inexpensive adequate instruments supplied by taxpayers, and why King or JP or someone ought to come up with the three valve compensating fiberglass sousaphone that can be used indoors and outdoors.

[iiipopes]

...the "King spin" is archaic.

Only if people are sitting to close to me and the composer decided that to not let me play at my best, which is during (ridiculously) long rests or tacets.

If only manufacturers swapped the piping on their valve-sets or the ports themselves.
But that would make things too complicated or it makes too much sense them to consider it.

*For tubas valve tubing that either point away from the ground or featured loop-de-loops

For a king, I prefer to hold down the 4th valve and dump the water back through the leadpipe. Better than spinning

Having suffered King tubas in high school: great tone, great intonation, built to take the wear of students. But that loop-the-loop is still archaic.