I noticed that in some countries tap water isn't safe for drinking but good enough for cooking; and everyone buys large plastic 40lb jugs of water for drinking. How much more cost effective would it be to adopt such a system as opposed to safe drinkable tap water?
Non-drinkable tap water is mostly due to water not being available 24x7x365. If a water system is turned off even momentarily, the pressure drops to zero, and sewage and groundwater seep into the water pipes, making it unsafe to drink.
Countries with unreliable power grids usually don't have drinkable tap water for that reason.
It can also be because the water isn't treated (ie. it is just rainwater in the pipes). Water treatment actually isn't very expensive though - collecting the water and distributing the water are by far the biggest costs.
In the west water systems are pressurized using a large reservoir and gravity. I imagine its similar in third world countries? They have unreliable water due to the reasons they have unreliable power: poor ability to plan, not enough supply, undersized systems for current use, deferred maintenance, etc.
Just because you can drink the tap water, doesn't mean you want to drink it. Sure, if you are desperate. But most who have the means will prefer to purchase the better tasting and cleaner water from gallons, rather than drinking the treated water from the tap.
The pipes network is very long so small leaks will always happen somewhere due to accidents or wear and tear. These small leaks are enough to contaminate the downstream pipes if the water pressure drops and dirty water get in.
Mostly the water is more or less safe but chlorine is added in many countries. That won't kill you but it's not very nice. And those big containers of water are affordable enough that they are preferable for cooking/drinking. I'm currently staying in Portugal and I'm buying a lot more water than I normally do. Back in Germany, the tap water is fine. But I do buy a lot of sparkling water because I like drinking it. Also, my urologist mentioned that bottled/filtered water is a great way to reduce the chance of kidney stones. The same calcium deposits that eventually destroy your washing machine might cause you some issues with those. So, there's that.
It isnt thay simple. As i kid we had non-potable water in the pipes. (Middle east) It was recycled water heavy on chlorine, safe for washing but not drinkable. Pressure was never the issue. We drank from a "sweetwater" tap, which also fed the hot water tank and the dishwasher.
Using safe potable water to flush toilets is silly. Splitting drinking from other uses is far more efficient.
> Splitting drinking from other uses is far more efficient.
This isn't universally true. Pipework (laying+maintaining), collection and storage is generally the expensive bit of any water system. The actual purification is fairly cheap.
That means having two sets of pipes to every house (one for drinking water, one for mid-grade water) usually costs more than just one set of pipes and having all water drinkable. Thats why it's rarely done.
The alternative is you use the pipes for non-potable water, and tell people to buy bottled water for drinking - more than half the world is in this position I believe. It helps that people drink perhaps only 1% of the water they use - so bringing 1% of the water via bottles on the back of a motorbike is viable.
That isnt how it is always done. In not-dry countries, the non-potable water is generally collected locally. It is filtered rainwater from cisterns, not piped public water from afar.
