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Discuss Gas pipe under/in solid floor in the Gas Engineers Forum area at PlumbersForums.net

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Hi.
I have been on the phone to the Gas Safe Register, who have pointed me a bit in the right direction looking for certain information.
I am in a situation where I have had a water pipe burst under a solid concrete and tile floor. The gas and water pipes were laid right next to each other in the early 60's, running through the cellar at the front of the house, through the back room subfloor (where the water pipe burst happened) and on into the kitchen, which is an extension.
The problems are related to the fact that the subfloor in the back room is composed of waste from old factories, which was apparently a common thing at one time, and it's a very silty soil with some degree of sulfates. This major leak happened a while back and it's never dried out, due to the soil type holding the moisture and expanding. I was told that due to all the waterlogged soil, it would prevent natural water drainage, and thereby force it up into the walls. The walls on the side of the leak were already bad from the leak water raising up into them, and they also have never dried out. The pipe burst in the corner by the door to the kitchen, and there, on the floor underneath the kitchen door, where there is no wall for the water to raise up into, water keeps seeping up through between the tiles, and has been doing so ever since the leak. It's in the door-frame too.

So it's definitely wet in there. A bit hole was dug in the corner to repair the water pipe, which was immediately next to the gas pipe, and it was bent to fit the connectors to join the new replacement bit of pipe across the bit where the old now-brittle pipe split. When it was done so, corrosion/rust was found to be forming already on the gas pipe. I have since been drying out the hole area by keeping towels on the pipes and originally on the mud, but as the rest of the subfloor cannot be vented or dried without ripping it all out, the gas pipe has been left trapped in there with considerable moisture and some degree of sulfates, which can apparently do chemical attacks. So it will be quite bad for the rusting in the subfloor.

As for the hole itself, the gas and water pipes are exposed in the hole. Unfortunately, due to the way they were fitted back in the early 60's the concrete of the original floor is quite shallow, only about 2inches maybe, and the pipes are in the silty soil beneath, the concrete was practically sitting on top of them. So they're not at a practical level for putting things right. A new patch of concrete laid over the top would separate from the rest of the floor and move, due to the unstable nature of the subfloor, and ultimately crack the pipes.

But before that, I have issues raised about regulations and safety as required by law and procedure.
I have been told that it is currently against the law to concrete over gas pipes, due to chemical corrosion damage. The way the floor would have to be done, if in the worst case scenario that an attempt to patch the hole was made, it would mean that the concrete would have to be considerably thicker to give it some strength without the surrounding concrete, or it would simply all crack. That would mean encasing the gas pipe in concrete, which as I understand it is not allowed now.
Also, I have been informed that the pipe needs to be wrapped and then sleeved, which would help take up some degree of movement from above. The pipe is a 3cm diameter steel pipe. Ideally the whole run of pipe should be replaced to get rid of the corroding steel, and make it safe. But I'm covering this from both the standpoints of if the gas pipe is replaced, or if it's not, and the floor (or part of) is relaid across the top. So I need some info.
What would be the diameter of a sleeve for this pipe after it's been wrapped please? I need to factor it in for issues with the relaying of the floor and the location of the water pipe, which has to be sleeved as well under current regulations. The water pipe has already been looked at, and I have the required specs for sleeving that.

There is some stuff online relating to gas regulations, but there's a lot to sift through. Does anyone know where there are pages to the official legislation, relating to the specific things I have raised above; the concrete doing chemical attacks and sleeve requirements? I've been looking through but there's so much to go through.

I have already looked into the idea of re-routing the pipe elsewhere, or switching over to electricity instead, but neither are viable options due to certain geographical factors, it needs to remain below the floors of the back room and kitchen.

Thanks for any help :)
 
As the pipe is steel you will be fine would recommend a gas safe engineer test the gas system for leaks eg tightness test and then wrap the exposed pipe with gaffa tape and re concrete with a weak / screed mix
 
I'm not sure about it being fine, there was a lot of copper coulored water all over it, and signs of considerable discolouration. I don;t think it's staineless steel. It oddly doesn't look like steel, it looks like lead. THe floor would still move and crack it though, that's a big problem regardless of what the pipe's made of, so that still needs sorting somehow.

As for a Gas Safe Engineer, both my local gas network company and the GSR said to get one out, but I've tried nearly 20 so far and had no luck. Nobody wants to come out to investigate it properly.
 
Is the gas pipe magnetic?
 

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