Are you sure it was all replaced and not just the top bit? Looks like some form of chemical reaction occurring

mattwnz:

 

Are you sure it was all replaced and not just the top bit? Looks like some form of chemical reaction occurring

 

All of the chimney and lower flat flashing was replaced above rectangular longrun roofing iron.

Whatever the problem is, it appears to be attacking the longrun roofing as well.

The previous chimney installation had lasted over 22 years - but this repair only 3 years.

mattwnz:

 

Are you sure it was all replaced and not just the top bit? Looks like some form of chemical reaction occurring

 

What does the other side of the upper flue section look like, is there anything running down from the top?

Time to light the Bat searchlight. Calling @sweep

Bung:

 

mattwnz:

 

Are you sure it was all replaced and not just the top bit? Looks like some form of chemical reaction occurring

 

 

What does the other side of the upper flue section look like, is there anything running down from the top?

 

Time to light the Bat searchlight. Calling @sweep

 

Looks like something dripping from the top of the chimney.

He must be burning something that is releasing some corrossive stuff.

Did they change the interior flu when they replaced the top of the chimney?

It looks awfully like fumes and soot are leaking out though that joint, which is then accelerating corrosion of the metal.... and when it rains the soot is then washing down the roof..

Have you been on the roof when the fire running to see how the chimney is working ...

I'm guessing that the corrosion on the lower part of the Chimney is away from the direction of the prevailing wind?

wellygary:

 

Did they change the interior flu when they replaced the top of the chimney?

 

It looks awfully like fumes and soot are leaking out though that joint, which is then accelerating corrosion of the metal.... and when it rains the soot is then washing down the roof..

 

Have you been on the roof when the fire running to see how the chimney is working ...

 

I'm guessing that the corrosion on the lower part of the Chimney is away from the direction of the prevailing wind?

 

He says that the internal flue was not changed. That could explain his problem for sure.

i suspect this is your issue, its a galv roof and flue and its being attacked by whats in the exhaust gas as it potentially condenses on the flue.

"Burning of green hardwood, resinous soft woods, low grade coal or oils with a high sulphur content can all result in greater quantities of fallout which contain corrosive substances."

Perhaps the guy that repaired the chimney should have been pro-active with recommending that the internal flue be replaced.

I think it is more to do with what they are burning rather than the state of the flue.
It looks to me like they are burning something that is producing an acidic condensation on the top cowl (hat) that is dripping down and attacking the galvanising.

@Swept my have more insight.

Also looking at what appears to be soot siting on the rubber boot, it looks like the flue is due for a clean.

I think there is a chimney sweeper that sometimes comes onto here. But it does appear, as others have said, that there is something wrong with the internal flue.

Gordy7:

 

He says that the internal flue was not changed. That could explain his problem for sure.

 

Sorry Swept memory not quite close enough.

If the internal flue was holed I'd expect it to show up above the fire inside.

mattwnz:

 

I think there is a chimney sweeper that sometimes comes onto here. 

 

Why do you think people keep tagging @Swept?

I have spoken to my friend... he was pretty impressed with the info above from Swept...

He says he gets the chimney cleaned evey year.

Sounds like he is going to use the fire for another couple of years, rip it out, replace the damaged long run roofing and fit a heat pump.