1000 liters an hour is 24000 liters a day. Ten million people showering with 8 liters (which is already pretty thrifty) a minute for three minutes is 24 million liters a day
LPT: When starting a shower or bath, turn your hot water to the max to heat it up faster and save water. Don't just turn it to your desired setting and wait. Wastes water.
You have to clear your hot water line of all the room temperature water first. Depending on how far of a run from your water heater your shower or bath is, I can be a lot of water. Millions of people saving a little bit of water adds up to a ton.
Say you like it on medium, half hot half cold. If you turn it to that setting at the start, you are slowly discharging the room temp water in your hot water lines while dumping cold water out for no reason.
If you go max hot at the start, you efficiently clear the hot water line the fastest. Then, you can add cold water to get your desired temperature.
There are two main hot water heater systems. Tank and tankless.
Tank - Depending on the size of your home, you'll have a different size tank. The way it works is that it stores X amount of gallon of water at X°. Average is like 40 gallons at 140° F.
Tankless - Again, different sizes depending on your home. It produces hot water on demand and doesn't store any hot water.
Doesn't matter which one you have. Max hot is going to be best.
From your water heater to your fixture, there is a pipe.
This pipe is always filled with water.
If you haven't used the fixture anytime soon, the water in the pipe will become the temperature around the pipe.
Most likely, the pipe is in your house, basement, or crawl space. All these places are less than 140° F. The water will not be "hot"
In order to deliver hot water to your fixture, this "room temperature" water in the pipe has to go, and you need to fill the pipe with hot water from your water heater.
Your shower or bath has a mixing valve. It takes pure hot water and mixes it with cold water to give you a desired temperature.
So say I go to my shower and turn it to medium, halfway between max hot and cold. What's happening is that the mixing value is letting equal parts hot and cold water through. (If you have a shower with separate knobs it would be like turning both knobs equal amounts)
It is slowly clearing the pipe between the hot water heater and your fixture because half of the water is cold. The fixture can only put out so many gallons per minute.
Now, if you go max hot, it is only clearing the pipe between the hot water heater and your fixture.
Say the pipe between my hot water heater and my fixture holds a gallon of water.
Say my fixture can output 1 gallon per minute.
This means that if I go max hot, I will have pure hot water to my fixture in 1 minute.
Now, with medium temperature selected from the start, it is going to get rid of .5 gallons of water in the hot water pipe and .5 gallons in the cold water pipe in 1 minute. To clear the whole gallon of "room temperature" water in the hot water pipe. It's going to take 2 minutes.
After 1 minute on max hot, turning your value to medium will instantly mix in cold water, giving you the desired medium temperature basically instantly.
The difference is that you lost a minute waiting for it to heat up, and you wasted a gallon of cold water for no reason.
The cold water you wasted costs money
And you had to get rid of the "room temperature" water anyways
Bro, what? The hot water is already hot, and no, the cost does not change much. The only difference is the storage cost; the energy input will be the same to heat it up (of course, depending on the heat source, the price can change - solar panels, electric, or fossil). And no, your showering is not really a problem. I don't know where you live, but where I live, personal household use accounts for about 3-5% of the water supply, so saying reducing the shower time or whatever will have 0 impact on water availability.
This is why it drives me insane when ppl say "I only use real dishes, never use plastic. Blah blah blah" I worked for an appliance company one day our factory dent is an entire shipment of plastic handles that wld need manual labor to assemble and the company just junked them. Didn't send them back, didn't have a team work on them, just straight up trashed the whole lot.
I was in the military and I've worked at Wal-Mart before that. The sheer scale of government and corporate waste would blow your mind, yet they can't shell out for clean drinking water on base.
Ok... and? It sounds like you are saying your company bought a shipment of plastic, junked it, and you're somehow using that to justify buying plastic.