Natural gas lines - 3 pipes?

They are putting new gas lines near my house. They are running 3 pipes instead of 1. Any reason for this? Is it for safety reasons? The pipes are about 8-10 inches in diameter and are spaced pretty close together. We are a fast growing area so I assume they need more capacity.

There is a lot of information here but nothing about running multiple pipes.

I’d assume they’re just going to three different places. It may have simply been more convenient to split them further back.
Also, one huge pipe would need to be buried deeper than three smaller ones. It would also mean they can shut off the gas main individual areas instead of whatever all three of them serve.
It may also be for safety, single, broke 8 inch pipe would (maybe) spew less gas than one 14 inch pipe.

But my money is one them going to three separate places.

Also not impossible they are using pipe that’s already in hand. Sourcing and running one pipe with the capacity of these three may result in delays and added costs. An expedient solution may what’s required at the moment.

It might not be the same gas running down these pipes. AFAIK at least for household gas it is some mix of butane, propane and possibly methane? So price can differ too.

I don’t know about Europe, but in North America it’s not like putting gasoline (petrol) in your car where you choose regular, mid-grade, or regular. It’s just Natural Gas, which is mostly methane.

Maybe three different pressures?

Did they have a whole long trench open, or just occasional holes? It was quite common to re-fit older large-diameter lower-pressure lines by using them as a sleeve for smaller higher-pressure lines (in the US, “street” pressure is regulated down at each customer to “house” pressure). Then they just need to make small holes in the street where each customer has service tapped off the older line to connect to one of the new inner lines. This is called “sliplining” and you can read about it here and here, for example.

it’s a big trench they are using for all 3 pipes

Where (roughly) are you located? Specific local geology and topography can have a huge bearing on what types of distribution piping can be placed in a given area. It’s often easier to stabilize multiple, smaller pipes than one large one. As Joey P suggested, this could easily be a safety issue.

I also wonder if this might be a regulatory issue. Several smaller diameter pipes with smaller individual capacities may be easier to permit and might require less frequent inspections and re-certifications. I honestly have no clue on this but it doesn’t seem impossible,

Raleigh NC area the soil here is mostly the red clay type. they are not digging up roads for this , they must be tunneling under them from what I can see. They are going through neighborhoods on land I assume was set aside for this as easements when the houses were built.

If they’re using a horizontal directional drill (ie a torpedo) to get under the roads, it may simply be easier to use 3 smaller pipes rather than one large one. Also, that means they’re using rubber (or whatever it’s actually made of) pipes instead of steal or cast iron. That may all play in to it.

the pipes look as if they could be rubber rather than metal. They are a light Army green color.

They’d have to be. If they were rigid metal, the ground would be torn up since they’d have to be laid in, one at a time and coupled or laid on the ground next to the trench, welded and then lowered in.
With a torpedo/horizontal directional drill they the drill down a few feet, straight(ish) however far they need it to go, then back up. Then they attach the pipe to that and pull the drill back and pull the pipe with it. If for no other reason than the beginning and the end, a rigid pipe wouldn’t be able to do that.

If you look near by, you may find very large spools, either empty or with the pipe still on them. Something like this.

I assume it makes sense that you can’t put a rigid pipe in spot that would cause it to bend, but if you do a google image search for horizontal directional drilling, you’ll see a lot of good pictures.

Gas pipes used to be metal. But if they are made of tough stretchy plastic, then they don’t break when the ground moves.

In Japan, that’s because of earthquakes. In my city, it’s because of clay soil movement. In other places, it’s because it’s the cheapest, easiest, most robust and therefore standard way of doing it.

Our water mains are made of plastic now, but it’s a different plastic which isn’t as stretchy, and if it’s pulled really hard it comes apart at the joins. Gas pipes don’t do that.

Phenolic-coated (steel) line pipe. For smaller diameter (2 Inch and smaller) polymer tubing is sometimes used, but for 6" and 8" pipe, it’s steel. You can’t get the strength needed for the pressures used with polymer. The OD is coated with a phenolic resin (similar to plastic-coat) for corrosion resistance, and typically has a light turquoise to blue-green color. A foot or so from each end will be uncoated so they can be welded (the coating would be damaged by the heat from welding). They coat the welded areas using infrared heat lamps to fuse the phenolic.