For those who live in stories. To get to the hot water upstairs, you need to move the whole column of cold water that is sitting in the pipes. Over a lifetime that's a lot of filtered water back down the drain.
Unless of course you have a tankless heater installed near the shower upstairs (Or even a traditional heater installed upstairs for that matter).
Exactly why I only shower using a tarp that funnels rain water into a pit I have dug in the back yard.
Unless you take very short showers, the amount of water in the pipe is a pretty small percentage of the water used while showering. Still, there are many things that can be done to minimise the water and heat used. Other than not showering, I mean - you could turn down the water pressure, turn off the water while you soap up, insulate the pipes, use a solar pre-heat system....the showering with a friend idea sounds good, but in my experience, that only uses more water. And energy.
How is your water pressurized? Is upstairs water driven by a different pump than downstairs water? If not, it doesn't matter.
The instructor for the energy efficiency in building systems class I was taking mentions that at home he has a button that starts a pump that redirects the (too cold) water from the hot water side back to the water heater. He figured it probably doesn't save much energy but at least conserves water.
If you want to save energy while showering, put the drain plug in (in the heating season). Let water cool down before releasing it. I once worked the numbers while I was showering, it works out that the heat in shower water will raise the temperature of the air in my house by 8 degrees. (This is not the same as raising the temperature of the whole house.)
I think he means that the water is potable and was filtered and treated upstream before entering the house. It's a bit unfortunate that houses don't have a secondary non-potable (but still somewhat treated) water feed for running toilets, showering, and watering plants.
this is why you buy a recirculation pump with a bypass... the pumps have timers... set it up to run in the morning before heavy usage (half hour or so) and at night before heavy usage. this way the pump forces the hot water back into the cold line so your water will be warmer or even hot-ish when you turn it on (depending on where you install the bypass)
That makes sense, but it's an over generalization. We have municipal water, but it's not filtered. Our water comes out of the ground and goes directly into the water mains. Other places I've lived used rather extensive processing before the water went into the mains, especially when the source was surface water. Tom
But it is 'drinking' water. Which is a limited commodity, or one that requires energy to produce, or both. It is best to be frugal with it; would you believe that there are actually places where people shit in their drinking water? It is also well to be wary of what a friend calls 'gizmodification', using a pump that required 5,000 gallons of fresh water to manufacture, in order to save 1,000 gallons of water at home is a losing proposition, even though it looks good because the manufacturing water is hidden.
I have showers on the ground floor and in the basement. My water heater is in the basement. I do not know how the pipes are routed. The downstairs shower is physically closer to the water heater (though not by much) but I do not know the length of pipe. I don't know if the two showers have separate pipes to the water heater, or if the pipe runs to one bathroom and then to the other. It seems to take about the same length of time for the water to get hot in either, so it probably doesn't matter which I use. Sometimes I just feel like using one or the other for no particular reason. I take fairly short showers and turn the water off while soaping up. I do this both to save water and energy, and because it's easier to soap up when the water is not running.
This varies dramatically by location and situation. Some places, every gallon is precious. Elsewhere, clean gravity fed unfiltered water is almost freely available in finite but more than currently adequate quantities, where every gallon not consumed is dumped directly into saltwater. The primary concern of these customers is to not waste energy heating any more of it than needed. Without knowing more detail about the local water situation, we can't fairly judge the value of water conservation. My own home water conservation efforts of the past decade were driven by energy conservation, and an unfair (and now abolished) water utility rate structure.
I am not sure that displacing the water column is the whole problem. After you displace the water column, you still have to run a lot of water to heat the pipes up. So insulation of the hot water pipes is one fix. I am most impressed. I might be able to do this calc in my pajamas, but not in the shower.
