Gas mains in basement - water leaking in at entry point; pipe itself heavily corroded

rr296

I am in the process of re-tanking my basement vault after the old membrane system (fitted on the cheap by the previous owner) developed a few leaks.
My builders have stripped back the old membrane and after we had lots of rain this weekend, it’s now clear that water is coming into the basement (only when it rains, to be clear) at the point where the gas mains enter the building. (and in a few other places as well of course for good order’s sake, but I am more concerned about the interplay between water and steel or iron gas pipes)
I live in a lower ground flat in an old Victorian building in London, and our basement is an old coal vault that extends under the footpath.  The gas mains enters through the wall at the far end of the vault where the footpath ends and the roadway begins.  
It’s not clear when this mains pipe was fitted (there are some remnants in one of the walls of what looks like an even older gas main), but it is heavily corroded to the point where it makes me wonder if it’s still safe.  
It’s definitely not leaking any gas (yet), but I wonder if it is going to need replacement in the next decade or so - in which case I’d be better off dealing with that problem now rather than fix everything in the vault and then have to rip it all up again.  
Below are 2 pictures of the pipe with the rust clearly visible.  The 3rd picture is where the pipe comes through the wall, i.e. where the leaks is.  In that area, the pipe is covered by some old insulation material which appears like it’s completely waterlogged from the inside.  
I’ll give Cadent a call as well, but I would be grateful if any experts on this forum could give me their view on how this looks to them.   And what you would recommend in terms of restoring / protecting the pipe to the extent it is still doable (and safe)?
Separately I was also wondering whose responsibility it is if there is water leaking in around where the gas mains enters through the wall of my vault.  Is that mine or the gas network’s (i.e. Cadent’s)?   Would they do something to fix that, or would they just tell me that’s my problem?
Thanks in advance!!

rob7475

You say you live in a flat - does that pipe supply just your flat or the whole building?
I'd get Cadent to come and look at it first. If they decide it's not safe, they'll isolate it for you. Usually, they would support until the point it reaches the meter but this may be different in a shared building.

rr296

my understanding is that this pipe services the entire building (5 flats).   
the coal vault used to be a common area belonging to the freehold, but the previous owner agreed with the freehold to have it demised to our flat.   both the gas and electricty mains run through it though, and that remains part of the freehold.
I'll give Cadent a ring today, see what they say.   

Another_Level

well it is corroded but is the pipe still in use ?  Where are the gas meters ? Is it just a short length of pipe as in photo ?
Really needs an expert to have a look and answer your concerns but see what cadent say   

southcoastrgi

Iron pipe with what looks like denso tape over it, it may well have had a plastic service inserted through it if it's gas, are you sure it's not water ?
If it is gas I'd be calling it in 

rr296

Thanks everyone.  I can confirm it is definitely the gas pipe, and it is in active use.   The gas meters is inside the flat, this is the main service pipe that comes into the building.   Cadent are coming to have a look this morning, let’s see what they think.

Another_Level

Well your acting responsible,  gas supply undertakers usually have periodic campaigns to renew their infrastructure including their supply to  domestic properties.

Maybe there is a plastic gas pipe inserted inside the old metal service pipe, the cadent operative will be able to establish by looking at the gas meter !!!!!! or by records   

  

rr296

Cadent technician came by this morning.   He said it's a steel pipe, not iron.   
Either way, his view is that it's just normal surface corrosion.    He jabbed his screwdriver at the pipe a few times, and when that scientific test failed to penetrate the metal that to him confirmed the integrity of the pipe.   "nothing to worry about" was his conclusion.   "just box the pipe back in once you're down with the works, and it'll all be fine"
he also did a quick leak test to be fair, which came up negative.
as for the groundwater leaking in around the pipe and causing the corrosion, "that's your problem not ours" was the resounding response.
thanks everyone for your input here.

FreeBear

Have just cut through an old steel gas pipe in my garden - It is thick wall tubing, so you will need to see an awful lot of corrosion before it becomes a danger.

The pipe I hacked through was disconnected many years ago, so I knew it was safe.

Another_Level

good to hear cadent have visually inspected, hopefully with your tank work that pipe has some protection.

Tbh, when the pipe is 100% dry it could be coated in a denso type tape, like petro tape from toolstation.

Seen similar pipe tape protection in the last photo.

When having your gas appliances anally safety checked/serviced you could include inspection of this pipe. property owners responsibility etc.