Copper joint woes - water in pipes advice

[shd1970]

Can anyone share any thoughts on how best to stop the final copper joint failing to take, due to water in the pipes on my central heating system ?

The system was fully drained....or so i thought !
I'd popped a tube in the final pipe and sucked out some water, i stuck my vac on it and got some more out and finally, i gave a good few blows in the hope that any remaining water that was "close" to my joint, would be far enough back in the pipe to allow the joint to go off but alas no, it seems the heat from my torch has a pulling effect for any water left

As per the title, the joint didn't work and then my pipes needed re-doing and I ended up using a compression fitting
Personally, i don't like compression and i didn't want a hotch potch of Pushfit either, ideally....i prefer old skool copper and soldered joint


This was for fitting a new downstairs radiator where the pipes are fed down from the ceiling

The problem i see is that you never know whether any pipes in the ceiling are fitted with any sort of gradient to aid draining, or if there are any "troughs" in the pipework where water can remain

I know for any pipes supplying taps, you can use the bread trick as you can get it out via the nearest/next tap but i assume this is not advisable for central heating pipes

Is the vac approach the best and thus should i just persevere for longer with the vac next time ?

Any thoughts/advice please ?

 

[polesapart]

yes, that last drip of residual water..

Tricks I have used include using earth sleeving as a straw, and pushing twists of kitchen paper into the pipe.

 

[HERTS P&D]

Peice of bread.

Andy

 

[shd1970]

yes, that last drip of residual water..

Tricks I have used include using earth sleeving as a straw, and pushing twists of kitchen paper into the pipe.

…and just let the kitchen paper disintegrate I assume ?
Won’t it clog the pump ?

I’ve got 3 more rads to do so that would be 6 lumps of paper in the system

 

[shd1970]

Peice of bread.

Andy

…won’t it clog TRVs ?

 

[HERTS P&D]

No, it dissolves.

Andy

 

[polesapart]

…and just let the kitchen paper disintegrate I assume ?

NO! Push a twist up half or a third of it's length and remove when sodden. Repeat until a dry bit stays dry.
Don't leave anything in the pipe!
Don't try using toilet paper which will disintegrate and not pull out!

I'm not recommending this as standard practice, just a trick I have used when all the normal suckee-blowee methods have failed and there's just enough residual water to make soldering a joint difficult.