Slide # 12 : Valve Circuit Map

Valve Circuit Map

Valve Circuits, for those who don't work in distribution, are the natural unit of work for water mains: they're the chunk of system turned off for repair when you walk a circuit around a break turning off every valve. It's also the natural unit of replacement, valve-to-valve. So, it works for both that, and the TBL cost of a break, counting a cost for every house out of water; I used $250 each, plus $25,000 for the repair cost. Multiply, say, $27,500 if there are ten houses by a 10% chance of a break, and the risk on that valve circuit next year is $2750. If it were 275 metres long, that's $10 per metre.

This maps several valve circuits by their dollars-per-metre risk value, with the red valve circuit being closest to being worth replacing, but the orange ones only worth the cost of anode retrofit. THe units at left are "RiskPerM", the risk in dollars per metre per year.