HELP!!! with undetectable sousaphone leak

[humnbass]

I have a 1949 Naked Lady sousaphone that I've been playing for 24 years. It has a leak that nobody seems to be able to find. I have it from shop to shop and everybody says it's fine. I know that there's a leak. I've been playing this horn long enough to know when it's not right. Any suggestions will be highly appreciated. The shops have been using a small light to go down through the tubing surrounding the valve section and lead pipe and looking for any illumination to pop through. Being that they don't see anything they are saying that it's fine but it's not. It's awful and does not have the sound and tone that I'm use to. Any suggestions will be highly appreciated.

thanks.

[sinfonian]

Could you take it to your local Y or other swimming pool. Sink it and let it completely fill with water. Try blowing through it and see if air comes out anywhere other then the bell. Just be careful getting it out of the pool when it is full of water.

[Dan Schultz]

Get an old spray bottle (Windex comes to mind) and fill it with a solution of water and dishwashing liquid (Dawn will do). Take out the main tuning slide and plug the open hole. Insert a mouthpiece and blow into the horn while 'spritzing' on some of the soapy solution. If you have external leaks, you'll see bubbles.

You won't detect leaky valves this way, though.

One type of leak that's almost impossible to find is if you have a perforation INSIDE one of the piston ports. One can usually spot that by just inspecting the pistons.

[Donn]

The shops have been using a small light to go down through the tubing surrounding the valve section and lead pipe and looking for any illumination to pop through.

That's funny! It's a good way to look for leaks in saxophone or clarinet pads. I wouldn't expect so good for a tuba, because a leak in a tubing joint could take a path that light couldn't follow. What's funny is that if you take a saxophone to a tuba repair joint, they will miss leaks that you'd think they could have caught with this simple procedure ... and evidently, a tuba fares no better in a saxophone repair joint, I'm guessing. Wonder why these two disciplines so often are practiced under the same roof? No one expects a tuba repairman to refit the sound post on a bass fiddle, for example, or tape up an accordion bellows.

[Dan Schultz]

.... No one expects a tuba repairman to refit the sound post on a bass fiddle, for example, or tape up an accordion bellows.

Hmmm.... in this small community... I not only do repair work on tubas... but also can fit a bass sound post and do accordion repairs. I keep a supply of parts for woodwinds but I would rather not work on them. Gotta draw the line somewhere.

However.... I know EXACTLY what you are talking about. Fifteen years ago I walked into my local 'large' retailer looking for felts and corks for a tuba and they acted like I was from Mars!

[Uncle Markie]

Old horns don't just leak at the joints. When you fill it with water, get some help and have them look for pinhole leaks in the branches, too. Horns rot from the inside out, too you know. Don't despair - that's what artfully done patches fix. Some guys can braze 'em shut, too.

Plus, I have been known to wear out slide tubes pulling them constantly to get in tune, plus dumping the water out - this causes leaks, too.

With today's prices, it might be feasible to have the inner slide tubes replaced if need be.

Good luck with your quest!

Mark Heter

[bobsacks]

I wonder if some sort of protective sealant either sprayed or brushed on would help?
I used duct tape on my baritone's leak and it worked fine but I think it probably has ruined the finish underneath.
I wonder if the material they use for car wrapping and protective clear auto bras would work?