I build hydraulic models of water systems for UK utilities (but live in Canada), one of the things we look at in the model besides the performance of the networ

I build hydraulic models of water systems for UK utilities (but live in Canada), one of the things we look at in the model besides the performance of the network is the age of water. In the UK, pipes are sized based on the needs of the domestic demand, while capacity for fire flow is not considered. While in North America the opposite is done, where the network, including capacity in tanks and pressure within the network, must take into account fire flow requirements. (The attached EPA document goes into this in more detail) While a UK residential street may be supplied by a 100mm main, the same street in the US may need a 200mm main. That's a four-time increase in volume that needs to be turned over in the pipe for just a little street! I have seen design documents for North American towns requiring flow rates of 50-90l/s to protect a single house. When I tell my colleagues in the UK about this they laugh and ask if I'm joking and if the fire bridge is aiming to simply flatten the house to stop the fire. Pressures in North American networks are also higher than in the UK, once again to meet fire flow requirements, which leads to higher background leakage and bursts within the network. High age of water is an issue that will affect most North American water systems regardless of if they are shrinking or growing.