I am about to start a complicated run in copper and it may take me a couple of weeks before I can get water in to flush out any flux added when making the joints.
Is it OK to leave flux hanging around in the pipes after soldering for this length of time, or is it likely to cause any damage?
I wouldn't be too concerned but it's always ideal to flush out as early as possible. Many new builds don't have water running in them for a long time or they'll be dead ends full of air left for quite some time.
A British gas fitter who convinced a mate he needed a complete new gas pipe run waffled on about how the old pipe was going through a cement wall and this was likely to corrode the copper. He then installs the new pipe and leaves shedloads of flux dripping down the pipe and doesn't even bother to wipe it off! Nice one.
It's difficult to wipe off the inside anyway...
Of course it is, but there's no excuse for not wiping it off the outside of the pipes, especially when you've put so much of it on that it's running several feet down the pipe.
Good point - how do you clean the flux from the inside of a gas pipe?
I assume that if it is fine to solder a gas pipe and never flush it out then leaving my water pipes soldered but not flushed for a few weeks will not be a problem.
The answer is to use it sparingly in the first place. Also, fluxes vary in their acidity. If the pipe and joint are well cleaned up with steel wool before soldering, you don't need a strongly acidic flux to burn through the copper oxide, and you don't need much flux at all. You also need good control over the soldering temperature and reasonably rapid heating of the joint, which is something which comes with practice.
Excess flux on pipework usually takes years to do damage. I've come across many collections of pipework which have been green with excess flux corrosion for probably 20 years, but not actually started leaking. If you also started with poor quality copper tube, that might speed up the failure.
If the copper is left in contact with cemnt or stone or whatever and it does not get damp, there is no likelihood of any corrosion from there is there?
I rather think the idea of taping the copper if it passes through concrete or whatever is to stop abrasion taking place should there be any juddering in the services.
The work done by the fitter referred to in the second post should not have been done without a pressure test first to see if the plumbing was leaking.
Use a non acid flux i.e not the self cleaning variety.
Better still,run plastic pipe!!
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| I am about to start a complicated run in copper and it may take me a | couple of weeks before I can get water in to flush out any flux added | when making the joints. | | Is it OK to leave flux hanging around in the pipes after soldering for | this length of time, or is it likely to cause any damage?
I once had trouble leaving the flux for some days *before* soldering. It took me *ages* the get the joint watertight.
Flux us supposed cause no ill effects to anything. If flushes out all well and good. If it stays put, all well and good.
Bollox. Best thing since sliced bread.
It melts when you solder it. And leaks when Drivel joints it with his hacksaw.
Though if careful, you can join it with a soldering iron.
Is this an appropriate flux then:
Don't let Drivel know. He'll try doing that with his blowlamp.
Paraffin one, no doubt.
Talking of DD.....
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