How to test for leaks?

[Tubajug]

How can you test for leaks once you've got the whole horn soldered together? I tested for leaks on the crooks I soldered back on by putting them in a cup of water, plugging one tube, and blowing in the other.

I found a leak in the first valve tubing where it attaches to the knuckle on the valve block, but that was only because I happened to have my left hand around there and could feel air coming out. Could I just put the whole thing in the bath tub and try to blow through it?

Thanks!

[Ken Herrick]

"Could I just put the whole thing in the bath tub and try to blow through it?"
You would probably find it had one heck of a 'leak' at the bell!

Fill it with water and see if any leaks out. Probably will be a bit at the valves and don't forget to plug the receiver.

[Dan Schultz]

.... I put the stealth tuba in one inch of water in the bath tub standing on its bell and used a bicycle pump to pressurize the whole tuba.....

Fair warning here. Even a very small pressure inside the large branches can spell disaster.

[Sam Gnagey]

Stuff a plastic ball down the bell and blow. You can use soapy water to spray over joints to pinpoint leaks where bubbles appear.

[Tubajug]

Stuff a plastic ball down the bell and blow. You can use soapy water to spray over joints to pinpoint leaks where bubbles appear.

Excellent! Thanks!

[Untersatz]

Stuff a plastic ball down the bell and blow. You can use soapy water to spray over joints to pinpoint leaks where bubbles appear.

Finally a "Sensible" answer Thanks Sam!