Gun Barrel piping for Central Heating: Vulnerable?

pfxh

My two-story house is 35 years old and has a central heating system based on gun barrel piping.
A neighbour of mine, with the same system, has got all of the gun barrel replaced by copper piping at enormous expense as he had experienced some leakage on the ground floor.
According to him, GB is prone to corrosion when in contact with concrete and won't last more than about 20 years.
Now, I did actually have a leak due to a severely corroded hot-water-in pipe on one radiator in our utility room a few weeks ago. However, while the corrosion (rusting) was intense for about 1 cm above and below the floor level, away from this region the pipes were in pristine condition despite their age and their life under concrete for more than 30 years.
I believe the corrosion we saw was due to the floor in that room having been flooded (washing machine) frequently over the last 20 years.
But, what I saw of the GB pipe's condition underground suggests to me that GB pipework should not corrode, or need to be replaced, once it is kept away from water.
I have googled a lot on this topic and there seems to be a range of opinions.
I would appreciate hearing other people's experience with GB.

RavenII

GB will last a long time as long as (from the inside) the heating water has no oxygen in it, so a long term minor leak with fresh water entering the system will screw it up. Same thing if it gets permenantly wet on the outside IE a leak wetting the insulation around it.

The water in the system should be clear if its treated with a corrosion inhibitor like Fernox or Sentinel....or grey/blackish if not (bleed a rad or take a sample from elsewhere to check) ....if the water is orange/red in colour you're heading for trouble ...that's oxygen-rust etc!

pfxh

Thanks for your reply.
I hadn't thought of putting in the corrosion inhibitor. That sounds a good idea.
Nevertheless, our water is slightly black/grey in colour and there are no leaks.
So, you seem to be saying that, as long as reasonable care is taken of the system, there's no reason GB piping won't last for 50 or more years.

RavenII

Yes, grey water is OK....what spells the demise of mild steel heating pipe is usually an ignored minor leak on a rad valve etc. ...the insulation gets wet and the steel rots.

Micky Dolenz

Start saving OP, You will need to re pipe the ground floor sooner or later.

JohnnieK

Stripped out a 40 year old GB system a few weeks ago as part of a refurb. It was immaculate. The old guy that used to live in the house (God rest his soul) looked after the system religiously. Cleaned every 10 years and inhibitor put in every 5 years. You could have washed your self in the water when I drained it down.

A central heating system would last forever if looked after properly.

pfxh

Thanks to everybody for the replies.
However, I'm seeing the same divergence in opinions that I saw when I googled about this.
@Micky Dolenz Your view is considerably more pessimistic than that of the other two contributors hitherto. Indeed, your opinion is in keeping with that of my neighbours who believe that GB in contact with the ground floor concrete will corrode over time.
However, as I already posted, I recently cut out a small piece of GB that had been embedded in floor concrete for more than thirty years and other than a very little surface rust, the piping was in almost-new condition with no visible loss in thickness.
Also, the notion that concrete corrodes steel seems preposterous as most modern buildings contain vast amounts of structural steel exactly embedded in the concrete and I'm not aware that corrosion is at all a problem.
It seems much more realistic to conclude, as the other two contributors have pointed out, that in the absence of water (due to leaks) on the outside of the pipes and the absence of oxygen (again due to leaks) in the circulating water, no reason for deterioration exists.

Alex M

Thanks to everybody for the replies.
However, I'm seeing the same divergence in opinions that I saw when I googled about this.
@Micky Dolenz Your view is considerably more pessimistic than that of the other two contributors hitherto. Indeed, your opinion is in keeping with that of my neighbours who believe that GB in contact with the ground floor concrete will corrode over time.
However, as I already posted, I recently cut out a small piece of GB that had been embedded in floor concrete for more than thirty years and other than a very little surface rust, the piping was in almost-new condition with no visible loss in thickness.
Also, the notion that concrete corrodes steel seems preposterous as most modern buildings contain vast amounts of structural steel exactly embedded in the concrete and I'm not aware that corrosion is at all a problem.
It seems much more realistic to conclude, as the other two contributors have pointed out, that in the absence of water (due to leaks) on the outside of the pipes and the absence of oxygen (again due to leaks) in the circulating water, no reason for deterioration exists.






sounds like you came on to get people to agree with what you think rather than seeking an impartial opinion

pfxh

@Alex M
Thanks for your comment.
However, your conclusion is quite wide of the mark.
If you read the thread, you will see that there are two "impartial opinions" emerging.
One, that GB if treated well can last a long time, is supported by experience from two posters.
The other, which seems to contradict this opinion, is delivered simply as a one-line suggestion without backup.
Personally, I posted here without an opinion at all and only a smidgeon of experience. If the work has to be done, I can easily do it myself with very little expense.
I just want to know what is the true viability of GB pipework under concrete. What I requested of Micky Dolenz was a clarification of his/her contrary position so that I could finalize my opinion.

Micky Dolenz

As already stated, GB will last a life time if it it protected during installation and maintained well. Mild flush every couple of years and inhibitor added annually.

GB rots from the inside out, If there is oxygen in the water it will corride the pipework, one leak will lead to many.

since you have already had a leak, it probably was leaked for a long time, constantly pulling fresh water into the system. This will cause problems.


I would start saving now, you may not have to address the problem for a few years yet, but an unmaintained GB system is nearing the end of it's life span.

I would now establish if the system has any leaks. To do this, tie up ballcock in small tank in attaic. Leave for 5 - 7 days, note how low the water level has got, if the tank is empty or near empty, you have a leak. You may lose an inch of water due to evaporation, you can still use your heating while you do this test.

If there is no leak, add a cleanser to the system, leave for a week, drain off. Refill using inhibitor.

pfxh

@Micky Dolenz
Thank you for your comprehensive and very helpful reply.
OK, so it seems we have a consensus on GB lasting as long as I do, or even more, as long as the system is well-looked after.
If you're not prepared to do this, then install copper piping.
As for my own system, I mentioned in my first post that the leak I had was from the outside, not the inside, due to frequent unattended washing machine leakage over many years.
This has now been rectified and the system has presently no leaks.
Indeed, the piece of pipe I cut out was in remarkably good condition on its inside despite its age. Based on what I've read in this thread, I believe this testifies to the fact that there is little immediate danger of a catastrophe.