How do you know a soldered joint is watertight?

[havingago]

It may seem like a silly question, but how do you know a soldered joint it good enough to be water tight?

I've done everything right, I've cut, de-burred, cleaned, fluxed and soldered but is there any sort of tool I'm missing to do that last check before putting water into the joint? It would save a lot of bother drying out the section and going through the hassle all over again.

I'm able to check smaller sections of pipe I've soldered together by capping one end then blowing air into them, it's a two man job for larger more awkward bent pipes, but I'm wondering is there any sort of tool that plugs into the end of a pipe and does a pressure test? Something simple like low pressure air (~2 bar) and a gauge would do the job to show it's not leaking.

Maybe I'm thinking out loud here, but what do the tradesmen do to test?

[htg engineer]

You can buy air test kits, with bungs etc, all you need is a U Gauge. Plumbers don't use them as standard as they solder all of the time, if they were installing pipe work that was going to be covered/hidden/buried and couldn't be commissioned then they would test the installation. If you have cleaned the pipe and fitting, applied flux and soldered so there is a neat continuous ring of solder round the fitting then there shouldn't be a problem - but as you say, once full of water, trying to get the water out to re-solder is when the 'fun' begins.

htg

[havingago]

Thanks again, I never knew what a U gauge or air pressure test kit was until now :)

Looking around it seems that for commercial grade wet plumbing (http://www.ukplumbersforums.co.uk/plumb ... -test.html) air testing is essential, likewise for gas; in my case it's only wet domestic plumbing (radiators, water supply) this is for so that I have the confidence in my installation.

I think I'll be investing in one of these air test kits (http://www.amazon.co.uk/Rothenberger-Dr ... 347&sr=1-2), although I need one that can connect to 22mm pipe and 3/4", any ideas on where I could find one, or, how to fashion one?

Thanks htg

[htg engineer]

I'd buy something like this:

www.google.co.uk/products/catalog?hl=en ... 7455373866

The U Gauge tube will fit snuggly over 10mm pipe, so using a 22mm - 10mm reducer you'll be able to connect the U gauge to the pipework.

Hope this helps

htg