Closed CHW system, failed solder joints

[ChasBean1]

Have a Closed loop chilled water system, several solder joint failures resulting in leaks. Joints I'm pretty sure are typical lead free pipe solder. 30% propylene glycol solution.

Water chemistry sample:
pH: 11.00
Conductivity: 5,900 umhos/cm
Total Alkalinity: 15,000 mg/L as CaCO3
Calcium: below reporting limit
Total Hardness: 3.0 mg/L

My thoughts: pH seems high, but doesn't seem high enough to eat solder, although I'm not sure how solder interacts with propylene glycol and high pH solutions. Conductivity and Total Alkalinity are very high - for closed loops I'd think conductivity would be <1,000 or so.

Your thoughts/experiences are appreciated! CB

 

[MJCronin]

Use threaded pipe...!!!

What diameter is your system ???

 

[ChasBean1]

A little late for that... Dia. varies, typ. runouts are ¾" and leaks have been in as big as 1½" joints.

 

[berkshire]

ChasBean,
If this is not a potable water system, why are you restricted to lead free solder?
Can you re-do the bad joints with 50/50 plumbers solder, or is there some other ecological reason, like a statewide ban on leaded solder?

Most times this is a workmanship problem, either the joint is not cleaned enough prior to soldering, or not enough solder is run into the joint to fill it. Lead free solder tends to have a higher and sharper melt point with less of a plastic range than 50/50, so it is a little more difficult to keep the solder in the joint. Pre-tinning the joints before assembly, tends to cut down on rejects, as does, using a tinkers dam to stop the solder running out of the bottom of the joint as you are filling it.
B.E.

 

[ChasBean1]

berkshire, thanks for the response. Sorry for my late reply. I think lead free is a common spec issue, not sure if it's a local code or not. You're right, non-potable, so it shouldn't matter although society's convicted lead as evil regardless of its application, so it's probably banned by some entity.

I'm thinking they may have had a nub running around with a torch, but no smoking (or in this case, leaking) gun yet.

 

[moltenmetal]

Wow- why is pH 11? Seems a might high...