I have just installed a dishwasher in my new kitchen. My second supply hose in 3 days has just developed a leak. The first time I thought it was a faulty hose (or the dog chewed it!). Now I am not so sure. I have attached a photo of the damage, which was identical on both hoses. The hose does loop over some copper pipes and I think that the site of the leak may correspond to where the stainless steel braiding and the copper are touching (see second image). Is it possible that heat is building up and melting the PVC inner? Should I lag those pipes to protect the supply line. Any advice welcome, as I want hose #3 to be my last and everything is going to become much more difficult to access soon.

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letmetellu

I could not tell anything about the second picture but the first looks like it could have been an electrical short, is that possible?
How long did it take for the first hose to develope the leak.?

chappers

Both of the hoses have taken about 2 days to start leaking. That is an armored electrical cable behind the hose in the first picture, so your suggestion is reasonable. However, the metal sheathing is itself grounded so I don't see how there would be enough current flowing from the cable to the hose to build up the heat (i.e. there is a low resistance pathway straight back to the electrical box via the cable).

speedball1

Well something happened to that braided shielded hose line. One of two things come to mind. Electrical short or electrolysis, the electrical interaction between two metals. My bet's on door number two. If it had shorted out to the point of burning through the cable it should have blown the breaker. It didn't so that leaves the interaction between the copper pipe and the grounded cable or perhaps the other way around. A grounded copper pipe and a ungrounded shielded cable. There isn't anything else left in my opinion.
If I were there the first thing I would do is take a AC Voltmeter and measure between the copper pipe and the cable. The next cable I installed I would insulate the cable from touching the copper pipe and see if things go better. Good luck, Tom

chappers

OK, thanks for the advice. I have more information based on my experimentation over breakfast....

This morning I went and examined the hose again and it was warm/hot to the touch, despite the hot water valve being turned off all night. I switched off the breaker to the dishwasher in case the short was from there. That made no difference and the hose stayed hot. I noticed when I moved the hose that it was getting really hot (glowing) where it was touching the copper pipe and would spark when I moved it against the pipe (not real arcing, just the kind of sparks you would get from striking a cigarette lighter). My chemistry knowledge suggests that electrolysis shouldn't be this dramatic or quick.

I think that option 1 is the answer and that the copper pipes are inadequately grounded. I think they are building up charge which is discharging via the dishwasher hose and then grounding via the frame of the dishwasher (which is definitely grounded). The two hot spots on the hose seem to correspond to where it's touching the pipe and where it's touching the dishwasher frame. If switching off the power to the dishwasher doesn't fix it, the current must be flowing from the pipes to the dishwasher. Right? This would seem to explain as well why the breaker is not tripping (i.e. it's static building up in the pipes rather than a short circuit from the dishwasher). My plumbing system is grounded in the basement, but I'm going to ground the two pipes behind the sink and also take your advice on insulating them to prevent electrolysis.

Does this all make sense?

Thanks!