Odd Cylindrical Object In External Water Stopcock Chamber

[chamois]

Yesterday morning I noticed a yellow chalk line had been drawn on the pavement next to my mains water outside stopcock chamber. Thought it a bit odd at the time.
This morning a couple of workmen were walking the street with one of them opening the lid of a so-marked chamber and the other guy fishing out a what looked like a 15cm cylinder about 50mm diameter made of stainless steel. There seemed to be a blue painted band around part of the cylinder and a hook at the top to allow them to fish the thing out. The cylinder was replaced on a double sided rack one of the men was carrying similar to a giant version of the type of rack used to hold sockets. The men then walked down the street opening random chamber lids, no doubt also marked with the chalk.
Can anyone suggest what these guys were up to please? There are no water meters on the street but I wouldn't have thought that water consumption at properties could be monitored this way or am I mistaken.

[RATTER15]

They are Russian listening devices! Don't say a word, they know where you are!

[woofgang]

checking and monitoring leaks?

[Old_Geezer]

If they are listening devices then they will be the cause of any leaks !

[Tilly2]

I would have gone out and asked them what they were doing. How frustrating, not knowing.

[gingejbee]

Sounds like members of the "leak detection" team at work.....

[EDDIE51]

I belive they are Ultra Sonic trackers and leak detectors ! The workmen will have a 'tracking unit' to follow it .

[KARL]

Aha, now we know Tilly is not British: She suggests actually walking up to a complete stranger asking a (therefore personal) question - how un-British :)

[Tilly2]

I'm an 'Up Northish British'. We do that sort of thing. :-)

I would have gone out and asked them. I'm nosy.

[KARL]

Tilly, I would have been out there at the first sight of them, who the heck is rummaging around my street, never mind my connection.....;)

Quite separately, there was someone I once knew who insisted the compass points toward more sense.

[Gill1941]

Why didn't you ask them?

[chamois]

Thank you all for your suggestions. I would have gone out to ask the workmen what they were up to if I hadn't received a landline telephone call from a relation in New Zealand just before I noticed the men. Unfortunately, my cordless phone is out of action and I had to use a corded phone - you might say I was "tethered" in the original meaning of the word!