How to do reliable silver soldering

[Arron]

Now the next hurdle. I need to solder some half inch copper pipes. These will be buried under render and behind tiles. I will need to do this about 4 times, each a few weeks apart (3 different rooms). I know that I need to use silver solder for a very strong joint, then cap it and pressure test before burying it.

I know I can call a plumber to do this, but last time it cost $90 for callout, $30 for gas, multiplied by 4 times is $480 - no thanks. I could also hire oxy - at $40 for the set, $90 for the bottles and $46 for deliver/pickup - by 4 times is $704 - not going to happen either.

So I pulled out my old Primus blowtorch and LPG bottle - and a Tahmore one and tried to solder some offcuts. Didnt work - not nearly enough heat - there is a joint but I dont believe it is reliable. Should it be possible to do silver soldering with LPG ? Is there some other type of silver solder that will work better then the stuff I have (the hard wire-like rods, cant remember if it is 5 or 15%) ? Is there an alternative to silver solder which I can rely on for pipes that will be buried ?

I would be keen to buy a different sort of blowtorch if I could gaurantee that it will do silver solder. Does anyone have a recommendation ? I have heard that Primus turbo torch will do the job - is this correct ? Any other recommendations.

I know I could get a plumber to do this - probably be the easiest way in the short term, but if I do that it leaves me with the job done but no new skills and no new tools - just the same problem arising next time.

I would appreciate someone giving me some guidance on how to do reliable silver solder without oxy.

thanks
Arron

[bitingmidge]

Arron,

Don't forget to make sure the whole pipe is wrapped in tape before you render over it, or better still stick it in a conduit.

Even if you get the job perfect, the lime in the render will eventually (might take a few years) corrode the copper and/or the joint.

Can't help you with the silver solder though, sorry.

Cheers,

P

[ozwinner]

You have to get both parts of the joint hot enough for the solder to flow, if you have to force the solder to flow you need more heat.

Dont forget that copper is a good conducter of heat, so it may take ages to get hot enough with a blow torch, but it can be done.

I would prefer brazing the joint if I was going to bury it, which require more heat than a blow torch can deliver.

Brazing wont come undone as easy as soldering, specialy when embeded in a wall.

Al

[knucklehead]

Brazing is the best bet.
It can be tricky if you haven't done it before so read up and do a couple of practice joints. You can get the silver solder rods with varying degrees of silver. Generally the higher the silver content the harder the solder (harder to use). The other thing is to prepare the joint really well. Get the right sort of flux and clean the joints REALLY well. This is what will allow the solder to wick deep into the joint.
P.S. the joints stay hot for a long time, have scars to prove it.

[Ashore]

1, silver solder comes in sticks or flat bar 5% or 15% ( this is the % of silver in the stick ) you are pushing it uphill with LPG
2, Primas made a turbo head years ago for small pipes but havent seen it advertised for years
3, Brazing needs more heat and more expertise with thin copper pipes and the strength of the joint is not as strong in my experience if done correctly
4, the rules
a, the job has to be tight fitting silver solder is not a good gap filler
b, the areas to silver solder must be clean spotlass fine emery followed by stainless steel wool both surfaces
c, u must use correct silver solder flux and only on the areas where you want the silver solder to run . Heat job slightly and apply flux then heat to temp to apply silver solder
d, never put direct flame on silver solder as Al says solder must run into joint . heat pipe touch solder stick on to the job and solder should melt and run into joint. Dont get job too hot as it will scale and then recleaning is needed
flame usually changes to slight green when temp is right if i remember correctly
e,low oxy flame is best but too low as you dont want carbon deposits on the pipe
f, some regulators wont let you use silver solder joints on drinking water flux or something
g, do not cool joint by any external means blowing on them water etc as this will cause hareline cracks weakening the joint
h, do not attempt to move joint or readjust while hot get angle and position right before starting



if you must ues LPG you will need 60% or better solder flat stick. More silver the lower the melting point of the stick
airforce and navy both use this grade or better so if you know anyone.......

if you are embeding them into a wall then the conduit is perhaps a good idea went to sea as a living so concrete walls arn't my go

If you buy some oxy think of all the great little jobs you will be able to do and all the new skills you will gain






He who dies with the most toys is nonetheless dead.

[RETIRED]

Why not use plastic with push on fittings, e.g. York and the like.

No corrosion, no soldering, bends round corners, only need a hacksaw and most importantly: NO LEAKS.

[DanP]

I have silver soldered thousands of copper to copper joints on high pressure steam, gas and water lines and have never used flux on the joints. It was rare that I had a leak. My method:

1. Clean the joint thoroughly with emery paper prior to assembly, including the inside of the female portion of the joint.

2. Use an oxy. You don't need a roaring flame. Apply heat to the joint relatively evenly, silver solder will draw into the joint if you have heated it right.

3. Apply a small dob of solder to the top of the joint and keep heating the pipe, not the solder, till the solder melts from the heat of the pipe. If the solder just sits on the pipe, heat over the part where the joints overlap until the solder draws into the joint.

4. Continue to apply the solder to the TOP of the joint and use the heat to draw the solder into the joint and around to the other side. If the solder goes all the way around on the inside of the joint you know that you have the strongest possible joint.


This is a method that I was taught by a bloke who had used it for years and I NEVER saw one of his joints leak. I myself used it for the better part of seven years and the only time I got a leak was if it was old pipe and I didn't clean it properly. If you're soldering copper to brass: Same method except use flux on the brass. The most important part is clean the pipes before you assemble the joint.

Dan

[wombat47]

Yorkshire fittings come with a ring of silver solder already in place. Add flux and heat with a pin point flame. Dead easy. But are they still made?

If you feel you have to DIY all the way, you will find that silver solder is quite soft, does not require a huge amount of heat and flows towards the flux - heat the joint and not the solder.

However, I think that learning silver soldering on joints which are going to hidden in a wall might be a tad risky.

Why not use plastic pipes, as used in many new homes. These use a chemical weld and I imagine there is some kind of compression fitting available to connect to copper piping. But note that these are a specific product specially designed to replace copper piping. It's not your average plastic conduit. I know my son's plumber friend loves them.

It might be worth paying a visit to a plumbers' supplier and seeing what is available and exactly how to use it.

[Mr Snrub]

Arron,
if you go to bunnings you can buy a BenzOmatic torch and a small cylinder of MAPP gas for about $80. While you are there get a stick of "brown tip solder" and some emry tape. this will give you good joins on copper pipe up to about 1/2".

The MAPP gas gives much more heat than the old Primus jobs and I use it for small refrigeration pipework which has to hold pressures of up to 2500 Kpa. Use the techniques that DanP suggested and you should be right.

[vsquizz]

DanP, Unsolder those coppers and let them out there on the streets...we need them

Cheers

[Kenya]

G'day Aaron

Tried to post a reply last night but the site or server crashed.

Mr Snrub is spot on about the MAPP Gas kit and price, most of the plumbers
I know now use MAPP. You can also get different tip sizes if you need more or less flame/heat.
We have just had some work done on 25mm copper pipe (natural gas line) and the plumber used a mapp gas kit without any problems.

Replacement bottle cost around $20 so the method is pretty cost effective.

Use 2% silver solder without flux, the joint must be really clean - that's the secret. As per DanP's procedure.

[Arron]

Thanks Guys. I have a day off today so went and bought a MAPP gas bottle and torch from Bunnies. That gear is brilliant and all problems are solved.

I expect the plastic pipe could be a good solution but I went the MAPP route as I have experience with soft solder and feel comfortable with soldering - I just needed to upgrade the heat to get the silver solder happening.

thanks
Arron