Approx. 15 to 20 litres are used in a single shower
It depends on how much water comes out of your shower head.
To install and use two shower heads in one shower, you will need to install a diverter valve that can control the flow of water between the two shower heads. This will allow you to switch between using one shower head, both shower heads together, or just the other shower head. This setup can provide a more luxurious bathing experience with the option of different water flows and angles for a more relaxing shower.
Only as much as some one allows the water to run
If the faucet contains the re-direction valve (closes off the water from the faucet and redirects the water to the shower head) you need to rotate the faucet counter clock wise to unscrew it from the plumbing and replace it with a new one. Take the old one to your local box store and they can match it up for you.
Shower filters are great for reducing chlorine in your shower. You need one that has KDF media in it to be effective not just carbon.
Shower, because you don't need the water below the surface and it is already dirty. It's like sitting in your own used dirty water so you'll be dirty anyways so why use water. If your taking a shower your using clean water and you can turn off the water when you don't need it.
To replace a shower valve with a new one, you will need to turn off the water supply, remove the old valve, install the new valve following the manufacturer's instructions, and then test the new valve for leaks before using the shower.
you need one cup of water to germinate a seed
One is "Save water: shower with your couple".
To install two shower heads in one shower, you can use a diverter valve to control the flow of water between the two heads. This will allow you to have multiple streams of water for a more luxurious bathing experience.
To remove a shower diverter, you will need to turn off the water supply to the shower, unscrew the diverter handle, remove the diverter valve, and replace it with a new one if necessary. Make sure to follow the manufacturer's instructions and use the appropriate tools for the job.
There are a lot of shower installations out there that were done in a time when efficiency was not the order of the day. Because of this, many showers out there use way too much water, and allow way too much water to spill out of shower doors. Generally, if your shower was installed before you bought your home then you may want to consider getting a new shower installed. If you rent, ask how old the shower is and see if you can work something out with your landlord to have a new one installed. Old showers can also hold serious levels of mold, so be careful.