Normally people don’t notice their water systems. As a water treatment operator I take is as a sign that I am doing my job well. There are however times where the water stops flowing. These situations range from simple watermain breaks all the way to a total shut down of the system. If the SHTF or TEOTWAKI situation is severe enough this is what I think will happen.
First some background information, there are two main consumables at my treatment facility, treatment chemicals and power. The chemical with the shortest reserve is a 3 week supply for the disinfectant. This is a hard limit which cannot be extended by using less disinfectant as the chemical degrades with time. The only way to extend this is to get more supply. On the power side, we have a diesel generator with a 14 day supply of fuel if it was running 24/7.
If the SHTF is such that we cannot go to work to keep the facility operating then after three days water quality will start to degrade, as the chemical day tanks start to run empty after three or four days. This will not be noticed as there will still be a four or five day supply already in the reservoir. So doing some simple math, after 4 days the water is situation normal, but is starting to degrade, after 6 days the reservoir is half full of untreated water. After 8 days the reservoir is full of untreated water. At this point the water will not be safe to drink, but the automatic systems will still be pumping water into the distribution system. At home all you would need to do is boil your water for it to be safe. After 14 days the generator stops and the system shuts down. Water will flow for an additional 60 seconds at most. This is it. No more water. You had better have/find a new source now.
In my opinion it is much more likely that we will be able to go to work to extend the facility run time. If it is possible for me to go to work I will. Even in a SHTF scenario I will go for two reasons. First, so I can get a lot of clean drinking water for me and my family, second, if I don’t go to work other people could die. Protecting the integrity of the systems I am responsible for is something I take very seriously. So now the total shutdown gets delayed as I can 1) institute water use restrictions extending the reserve times. 2) refill the chemical day tanks 3) arrange for more chemicals and fuel. I can keep the water on as long as I can keep fuel in the generator, if I can’t then I am still held to the 14day fuel reserve. I can keep treating the water to pre-shtf levels as long as I can obtain more supply.
In a scarcity situation and many users need fuel for generators and cars, I will be bumped up to the top of the list, because all I have to do is ask the truck driver/owner/attendant how long he wants to have drinking water, it will not be a hard decision for him to make. The other thing I have going for me is I have prearranged suppliers, and backup suppliers, and in some cases another back up supplier. We have planned for major disasters and disruptions to supply chains, but you can only plan so far.
Where you live the timeline will be different. If you live in a large city then the timeline will be short, but they will have more influence with getting more supplies. If you live in a small town your time line may be longer but they will have less influence for getting more supplies. Look around, How bad is the TEOTWAWKI? Are trucks still delivering goods? Can you still buy fuel (regardless of price)? Like I said, if i can get resupplied then the water will stay on. If I can’t then I suggest you have other arrangements made.