I installed two of these water lines from my hot water tank to the water supply and hot water out lines in 2010. After several months I noticed a black greasy/rubber debris coming from the hot water from the faucets. This got so bad in the master tub that we stopped using it. The tub would fill with black residue. If you touch it, it will smear and become difficult to remove. The black residue could also be found in the screens of every faucet.
This has been driving me and my wife crazy for almost 4 years. After some recent google searches, I found the source to potentially be the Shark Bite hot water line. Sure enough, after replacing the Shark Bite water lines, the black debris is GONE.
A significant amount of black residue came out of the Shark Bite water line that come from the hot water side of the hot water tank. To confirm the black residue came for the water line, I placed a screw driver inside and scraped the inner wall. The same black residue could be torn from the inner walls.
When I went to Home Depot to get replacement water lines, the department rep said that I was not the first person to make this claim. The water line within the braided stainless steel is a black rubber instead of the typical white plastic that every other manufacture uses. Unless you can confirm this product has been redesigned, DO NOT USE it for the hot water supply line from your hot water tank.
I wish I would have taken more photos, but see the attached photo of the black residue that spilled onto the top of the hot water tank when I removed the Shark Bite water line.
One final disclaimer, this only applies to Shark Bite water lines, not fittings. I have several fittings throughout my home that have no problems.
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