Electrolytic pipe failure?

same happened in my house. A copper pipe feeding the water heater was just "touched" by the tip of a nail (steel/iron). It took some years but eventually the two dissimilar metals formed a tiny battery (also as I live one block from the ocean there is likely some salt in the air) and tiny hole was etched in the copper pipe. Water started dripping down all the way to the ground floor.

Agreed. Very strange failure mode.

Jeff Groves

In the 70s and 80s Pitting of copper water pipes was common, in my area of the USA, to houses that had shallow wells, maybe as shallow as 18 ft. and not to houses that had municipal water or deep wells. All of the shallow well houses eventually had the copper water pipes replaced with PVC because the number of pitted through holes progressively increased. We had attributed the pitting to the acidity of the shallow well water. Of course we had no real understanding of what caused the pitting. I was working in the residential building trade at the time.

It wasn't that bad. It happened in the right place.

Big Clive

Could you maybe find a way of flushing all the pipe work with a corrosion inhibitor like benzotriazole which forms a coordination polymer with copper? Obviously you’d need to flush it all out thoroughly afterwards. But it might stop the progression of the corrosion.

My main source of hot water is an undersink vented heater in the kitchen. There is a hot water feed from the boiler, but I rarely use it. That might be the issue.

Big Clive

That seems like it describes what we see in Clive's cutaway exactly. This might be why most homes on well water in my area use PEX or CVPC piping, even in older installations. Municipal water supplies are almost all sourced from surface water here.

It might be this: <a href="https://en.wikipedia.org/wiki/Cold_water_pitting_of_copper_tube" rel="nofollow noopener" target="_blank">https://en.wikipedia.org/wiki/Cold_water_pitting_of_copper_tube</a>

In the -90 it was problem with unpure copper in europe. Small impurity of iron was common, in combination with thinner pipe walls it created problems like this.

Danger, Bad Joke Follows: You tried that magnetic water softener on your own pipes? Bad Clive! :)

Are there any non-copper fittings involved? In one of our houses, we have a forced hot water heating system, and the piping is copper, but the air remover is cast iron, and there was no plastic fitting between them. The galvanic erosion of the air remover pressure vessel would cause pinhole leaks. The comedy of me replacing it without being able to drain the system (I couldn't, for reasons I won't get into) would have been YouTube gold, I am sure. I took a very nasty shower and managed to stanch the flow with the cork from a bottle of Knob Creek, my regular bourbon.

That sucks! What a mess to come home to. I hope the cleanup is inexpensive and goes well.

Lostngone

Find this all the time in older building's where steel fittings and clamps are used on copper pipe, also where copper pipe has been laid on to galvanised cable trays. Also seen it where steal particle from old utility pipes have settled in the home pipe system.

I had a similar issue a few years back but that was due to an old nail nail having been left in one of the floorboards. It was barely visible but had gradually (over 10+ years) chafed a hole in the pipe, as people had walked over that board, which was in a doorway.

Maybe you lost the ground on your suicide shower head but I doubt you installed that after you took it to bits. Seriously though how do you make your hot water? Maybe this is a sign of the ceramic heating elements beginning to fail. Time to make a megger test video.

Aaron Nadler

I don't believe two ground rods is common nationwide. I have only ever seen one per residence in new construction in IL, IN, KY, and TN.

Andrew Sloniger

This seems to make sense. The cavitation would occur in the same spots after the initial damage due to the irregular surface of the spots, I'd wager.

Andrew Sloniger

Had you considered replacing it all with lead piping? :-p

A client of mine had similar corrosion in his house, in that case after researching it, he concluded that it was due to the system being commissioned, and then the "first batch" of water left in the system static for several months before it was put into normal use - this apparently caused the normal coating which forms on the inside of the pipe to not occur, and then the corrosion process started. The piping was about 4 years old when it started leaking. How old is the pipe in question? After several leaks, he chose to replace all the copper with PEX. That was in a hard water area however, and I understand that other forms of pin hole corrosion can occur in soft water areas...

I have made the same mistake, so I will share with you - lower amounts of dissolved solids isn't the same thing as soft water. You can actually have "soft water" with over 500PPM of dissolved solids, as it still has relatively low calcium hardness. This is still often more corrosive, as there are more aggressive chloride ions in this case. Purer water (low dissolved solids) is more corrosive because it can swing in pH rapidly (deionized water practically doesn't have a pH according the the pH meters and indicators I have used) with only very slight contamination (which is why you buffer your water in hydroponics) and is effectively a less exhausted solvent. I believe you are exactly right about the Flint water. They changed sources but did not adjust their treatment techniques to save money on pH buffering and balancing, from what I understand.

Andrew Sloniger

At least it's only a bit of copper pipe. I've recently replaced the entire lower end of an outboard engine due to electrolytic damage. I wonder if you can fit sacrificial anodes to plumbing as well, to save you replacing it all?

mikenco

There was a copper shortage in the 1970's in the UK, so heating pipework then was often made with thinner walls, or was not made with pure copper. If your house was built in the 70's suspect the latter as your pipe seems to be thick enough, but maybe impurities are in there which is what's failed. If that is the case, then this pipe is probably just the first to go, and others will follow unless you look at replacing them all.

This happened to me two years ago. We have cistern with rainwater. Replaced all our pipes with cpvc and haven't had an issue yet.

In my experience, more pinholes are likely to appear in time. Due to the lower quality of copper fittings of late. I feel somewhat more comfortable putting in PEX with metal fitting.

Vaughn B.

Not a plumber but I have done a lot of house refurb. I have seen this many times, it's always on old pipework, a you will know the water is soft in the west of Scotland, this could be a factor but I'm not sure. The green 'verdegris' is just where the air and water have come into contact with the copper together and formed copper carbonate, that's why it's a little crater round the pinhole. It's time to replumb, change to plastic barrier pipe.

The Tinkering Shed

In our building we find that pin holing tends to show only on our recirculation lines. I have read that this could be due an electrical potential as some sections are plastic and also there is constant flow and no anode in our very large concrete lined hot water tanks..tanks are in great condition, but minerals may be attacking something close. If your hot water tank has an anode it may be time to replace it as they are usually only good for 5 years depending on the water. One thing that helped us was to use the thicker refrigeration copper and there fittings. A bunch more money, but it should last. Especially with crap fitting that seem to have been sold recently smaller and slightly thinner. Old and new fitting sometimes even share the same upc numbers..

Vaughn B.

Here in the US, it was common practice to ground our electrical service only to the water mains. The code changed in many areas and now the primary ground is two six foot copper rods about 6 feet apart. Then they run another bond to the cold water pipe. I suspect the cold water pipe only was causing just those problems so now the two ground rods.

George Cohn

One theory I've heard that seems to hold water (or not!) is that water hammer can contribute to pinhole leaks in copper water lines. Water hammer is the abrupt and intense increase in pressure when a fixture valve is shut off. This spike in pressure creates a shock wave throughout the plumbing system as water is incompressible and the shock is transmitted effectively through it. The theory is that the acceleration from this shock can cause cavitation, pitting the inside of the piping. Initially, this strips the normal oxidized coating inside the pipe in a particular location or locations, and once that's happened, cavitation is more likely to occur there again due to turbulence from the existing damage. Homes that have a pressure regulator on the incoming water supply may be more likely to be affected as the pressure regulator prevents backflow to the supply side, isolating the pressure spike within the home. Pinholing tends to happen in the middle of horizontal pipe runs predominantly. Expansion tanks can help mitigate the pressure spike, as well as helping manage pressure increases due to water heater related expansion. There is some thought that unsupported or undersupported piping runs may contribute to damage due to water hammer too. That's how it gets its name. Loose piping will flex from the shock wave and bang inside the walls, floors, or ceiling.

Was thinking if you have soft water, that will cause corrosion in metal plumbing. When I was a water plant operator, the plant was a R.O. plant and would strip most everything out of the water and bring the PH to drop from like 10 to a low 6. We would add chemicals to bring it to between 8 to 8.3 . We did this so the system would keep a slight coating in the pipes to protect the pipes . Knowing what I know those people in Michigan were ok till there plants changed were they where the plant got its water from. Generally well water will be hard and when they switched to getting the water from the river, there water went from hard to soft ( corrosive) at that point the lead in the lead pipes would be able to dissolve in the water.

Cleveland Prescott

Had the same thing happen a couple years back. Horizontal copper pipe + damp/humid basement + 60 years = 3 pinholes. They were so small the only way I finally noticed it was that there was a sizzling noise from the fine mist spraying on the water heater flue pipe.

Jeff LaHay

Here in the states , for a bit had the ground buss at the main panel tied to the house water pipe. The pipe might run across a electrical pipe or something allowing a tiny current to pass through it causing galvanic corrosion, just a guess. A relative of mine who is a electrician, had municipal water and lived a good ways from the water plant and his house kept getting hit with lightning. He disconnected the connection to the water pipe and it stopped. We think the connection was causing his house to have the same potential as the water plant that was like 30 miles a way from him, which was causing his house to be struck by lightning.

Cleveland Prescott

I had never heard of this so I searched for "pinhole corrosion copper pipes" and found that this happens. There are several theories why but it comes down to you need to replace the copper pipes. Expensive, but so is water damage.

Mark Trombley

Or maybe the acidity of your water supply changed?