Geograph - photograph every grid square

A major campaign of replacing lost (that is, stolen by metal thieves) markers for the water infrastructure. These are so new that the nameplates are held on with cable ties, the secure bolts have not been fitted yet. Only some of the numerical inserts are fitted, only the one on the right is fully numbered, and that is still waiting for the "blanks" to go either side of the '3'. The top number is the fitting size in mm, the lower number is the distance to the manhole in metres. I am not convinced the lower number, at 3 metres, is correct.

The two-letter designations, left to right, refer firstly to a Wash Out fitting, a valved port to which a standpipe can be attached to purge contaminated lines. It is also suitable for a standpipe in the event of rationing. The next is SV, which is often taken to mean Stop Valve, or Service Valve, but is more properly called a Sluice Valve. It can be used to close the main pipe to the right while the Washout port is used to cleanse the incoming pipe from the left. The last, AV, is an air valve, used to bleed entrained air from the system. By keeping air out the main is completely filled with fresh drinking water that cannot go stale, and no airlocks can form and make alarming noises or cause weird supply events. I am astonished to see that an AV is 125mm diameter, I would have expected no more than 25mm.