comparing road melt to a buildings water use isn’t a perfect comparison.
I’m not going for a perfect comparison, I’m just going for an order of magnitude. I know that sanitary sewers and storm sewers are different (in fact my city is currently in the middle of a big, multi-decade project to separate the two).
But let’s do the math anyway. So, we’re not talking about the water from a sanitary sewer being super cold here. Water leaving a treatment plant is usually around 68-95°F because that’s the temperature required for the biological reactors that break down the gross stuff. Either end of that range is substantially higher than the melting point of water, so the snowmelt flowing from the storm sewer due to this under-road heating is going to be a great deal colder at release than the treated sewage flowing from the office building.
I’m not going for a perfect comparison, I’m just going for an order of magnitude. I know that sanitary sewers and storm sewers are different (in fact my city is currently in the middle of a big, multi-decade project to separate the two).
But let’s do the math anyway. So, we’re not talking about the water from a sanitary sewer being super cold here. Water leaving a treatment plant is usually around 68-95°F because that’s the temperature required for the biological reactors that break down the gross stuff. Either end of that range is substantially higher than the melting point of water, so the snowmelt flowing from the storm sewer due to this under-road heating is going to be a great deal colder at release than the treated sewage flowing from the office building.