Corroded hot water expansion pipe

[johnny2hands]

I’ve got a y plan system and have found pinholes on the hot water tank expansion pipe (and a leaking ceiling). I’ll replace it but am wondering if this is a symptom of something badly wrong?! It’s about 25 years old with an ideal classic that has been a bit noisy lately. Any advice?

 

[Madrab]

Expansion pipe? Which pipe specifically, can you post a pic of it?

If it's 25Years then it might be the vent but there shouldn't really be anything in there that should cause it to corrode.

 

[johnny2hands]

Hi, thanks for the reply - it’s the pipe that goes up and over through the lid of the HW tank. The holes are straight through the copper - not on a joint or dodgy fitting which was my first thought!

 

[terryplumb]

How old is the property ? Sounds like pitting .

 

[Madrab]

That's very strange, the only thing in that pipe is water from the cold water storage cistern in the loft and shouldn't have anything in it that would corrode the copper. Has the pipe gone green/black? Maybe something that was stored in the cupboard?

 

[johnny2hands]

How old is the property ? Sounds like pitting .

It’s 25 years old - original system.

 

[johnny2hands]

That's very strange, the only thing in that pipe is water from the cold water storage cistern in the loft and shouldn't have anything in it that would corrode the copper. Has the pipe gone green/black? Maybe something that was stored in the cupboard?

That’s the thing - it’s corroded in the loft near the tank, nothing up there but insulation and a few suitcases! I’m wondering if some old flux has eaten away over the years. The pipe is a bit green where the holes are.

 

[terryplumb]

Look inside the pipe ,you will likely see lots of little lumps ,each one eating away at the copper ,sometimes with a greenish colour around them. It's known as " pitting" and can be inherant throughout the Pipework, unfortunately.

 

[johnny2hands]

Oh. That doesn’t sound good! I’ll cut it out and have a look.

 

[johnny2hands]

Look inside the pipe ,you will likely see lots of little lumps ,each one eating away at the copper ,sometimes with a greenish colour around them. It's known as " pitting" and can be inherant throughout the Pipework, unfortunately.

I havent been back to sort it yet (i

Look inside the pipe ,you will likely see lots of little lumps ,each one eating away at the copper ,sometimes with a greenish colour around them. It's known as " pitting" and can be inherant throughout the Pipework, unfortunately.

Thanks for the replies yesterday. I’ve cut it out and on further inspection it was what you described. Out of interest, what is pitting - and what causes it? A relative of mine reckons (bear with me) that about 25 years ago, the uk imported batches of cheap/substandard copper and is/was causing problems if you were unlucky enough to get some in your property...anything in that or just an urban myth?

 

[terryplumb]

Quite a bit of investigative studies have been done on the subject of pitting in copper pipes not just in UK but in the States also ,and opinions vary and their conclusions include a whole host of theories including poor quality copper ,excessive use of flux and pipework not being flushed out , different metals in plumbing systems reacting added to a small voltage present in the Pipework and the water in the pipes acting like a battery ,microbiological reasons in hard water areas combining with minerals naturally present in some water supplies and a lot more that I have long since forgotten about. So take your pic,including that of your relative.
The upshot is, the only thing you can do when you identify it ,is strip out and replace.
I have come across it many times over the years ,always after customer had a pin hole leak. Most shudder at the thought of completely re plumbing the property, and instead just get sections repaired as and when another break through happens. I remember one couple who after a repair just put the house on the market and moved.