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Are SharkBite fittings reusable?
Are SharkBite fittings approved for underground use?
What should I do if a SharkBite system is leaking upon installation?
3 foot section of copper pipe that had developed a pinhole leak. ... Our water here (Vancouver BC) is really soft.
While it could be the fitting, my initial reaction to this confluence of factors is "Well, then copper pipe is a terrible idea, and replacing a single section of copper pipe due to a pinhole is doing nothing about all the other sections of coper pipe being eaten by the water."
Where copper pipe is eaten by the water chemistry, you either need to alter the water chemistry or use pipe that does not corrode. And if you are replacing copper pipe that has been eaten, you need to look large-scale, because every bit of copper pipe in your house has been exposed to the same water for roughly the same amount of time.
So my first guess would be that the leak is most likely coming from the pipe beyond the replaced section.
My view on Sharkbite Fittings:
They are great for exposed plumbing. Especially for water heaters. They make a great quick disconnect system for appliances. I also am a big fan of their shutoff valves.
What I would not use them for us concealed work behind walls and ceilings. They are rated for it it they claim the rubber seal will last more than 20 years and are resistant to deterioration from corrosive water. But I simply don't trust them. I want my pipes to last 50 years.
The key to a good sharkbite connection is proper preparation of the pipe. Of you're using PEX, it's a no brainer. If you're using copper, you need to properly debur the fitting. Inserting a jagged sharp edge of copper into the fitting can tear the rubber o ring inside the sharkbite fitting. Also, don't use Emery cloth the clean the end of the pipe like you do when soldering. This can also cause a leak.
It looks like the paint on the pipe is causing your problems. I'd recommend shutting off the water, removing the shark bite connector, and stripping the paint for a couple inches on either side. The hardware store will have chemicals to help strip the paint so you don't have to do it all manually.
Here is a video of how to use emery cloth to clean a copper pipe. The video is a bit long for the topic but covers it well: https://www.youtube.com/watch?v=Q4LvzHt4m3M
When you reinsert it, SharkBite recommends 15/16" insertion depth for 1/2" pipe. Typically you should measure that distance from the end of the pipe and mark it with a permanent marker so you have a sight line for reference when pushing the fitting on.
You can also use any number of abrasive or sanding products but that paint has got to go. The wall of the pipe has to be absolutely free of debris.