In most RVs, the two biggest consumers of water are both in one room: the toilet and the shower. RV toilets are already about as water-efficient as they can get, so there's not much you can do there, but I'll bet you can cut down on the water you shower with by quite a bit, even if you think you're doing a good job now. While we're at it, I'll show you how to save propane as well.
This page is titled "The one-gallon shower," but actually, the last time I checked, I was showering and washing my hair every morning with just 0.7 gallon. Of course, a lot depends on your hair. I'm bald on top, but my hair is shoulder-length around the sides and back. If you have a buzz cut, you can probably do better than I do. On the other hand, if you have thick, full hair, you'll probably need more water to wash and rinse it. Anyhow, let me tell you how I do it, and maybe you'll pick up some ideas.
I was never in the Navy, but most people refer to the kind of shower I take as a "Navy shower." That just means you get yourself wet, turn off the water, soap up and then turn the water back on and rinse. Ah, but there a few additional tricks I've come up with... so let's go through a typical shower, step by step.
Step 1: Heat the water to perfection
When I lived in a house, I left the water heater on all the time, like everybody else I knew. It never occurred to me to turn it off. And when I wanted hot water, I opened the tap and ran water down the drain until it got hot. Needless to say, I don't do that in my RV! I don't run water down the drain, and I only turn on my water heater for fifteen minutes a day on the average. The water heater is well enough insulated that once heated, the water will stay warm for most of the day, so there's no need to leave it running, wasting propane.
The secret is to run the water heater just long enough to get it to a perfect showering temperature. Then you can turn the hot water faucet on full—no need to fiddle with hot and cold, wasting water while you get the mix right. There are a couple of ways you can do this.
The first is to time the water heater. Turn it on, set your kitchen timer for fifteen minutes, and see what the temperature is like when the timer goes off. With some trial and error, you'll find you can pretty accurately judge how long it takes to reach the perfect temperature. Of course you'll have to make seasonal adjustments, because in the winter, the water heater will be starting with a much colder tank than in the summer. I found that with my six-gallon Atwood water heater, the time ranged from about 8 minutes in the summer to 20 minutes in the winter.
But there's a better way to do this: use a thermometer. Get an inexpensive digital thermometer that has a wired outside sensor, and slip that sensor under the insulating jacket of your water heater so that it's in contact with the tank. Now you can see exactly when the temperature is perfect.
Best of all, get an aquarium thermometer that has an audible alarm, like this under-$20 General Tools AQ150. Once you've calibrated the thermometer to your desired temperature, all you have to do each morning is turn on the water heater, push the "Alarm" button on the thermometer, and walk away. When it beeps, turn off the water heater, and you're ready to shower. All that's missing is the butler saying "Your baahth is ready, m'lord."
Step 2: Run it, but don't waste it
OK, the temperature is perfect in the water heater... but you have to get the hot water through the pipes to the shower. This is where a beverage jug comes in handy. I hold a one-quart Rubbermaid jug under the faucet and run the water until it's hot, catching what would otherwise have gone down the drain—about three cups.
I set that jug next to my kitchen sink, and use the saved water to wash dishes all day. This way, no water goes to waste.
Step 3: Get soaked
Time for the main act! I step into the shower and turn the showerhead's shutoff valve to "ON" to start the flow. (If your showerhead doesn't have a cutoff—usually it's in back—get one that does! It makes "Navy showers" much easier.) Letting the water run on my head, I turn 360° to get my hair completely wet (not to mention the rest of me). That takes about twenty seconds, and uses about a quart of water.
By the way, I ought to mention that I modified my showerhead so that it gives a vigorous spray with a small amount of water. In my previous RV I had a SHURflo "Whisper King" water pump that delivered 2.5 gallons per minute instead of the 4–6 gpm pumps found in most RVs. The resulting stream from the showerhead was less than forceful.
To remedy this, I made a simple modification: I plugged up half of the showerhead's holes with epoxy glue. Sounds inelegant, but it worked perfectly—the force of the stream was doubled with no increase in volume. It's a much better way to save water than putting a flow restrictor in the base of the showerhead. That saves water, but gives you a feeble spray.
Step 4: Lather up
Having completed my 360° turn, I shut off the water at the showerhead and start lathering up. I use a liquid soap (Dr. Bronner's peppermint castile soap) for both hair and body, but you can use your favorite bar soap and/or shampoo. I take about a teaspoonful from a wall-mounted dispenser (no juggling slippery shampoo bottles or soap bars), and lather up my hair to a fare-thee-well. Then I scoop off the suds and use them to soap up the rest of my body as necessary. Unless I'm really grimy, I usually just lather my face, ears, armpits, crotch area and feet (including the soles)... my torso, arms and legs get clean enough just from the soap and water runoff. (I'm a mostly indoor guy, so I don't often get very dirty.)
Step 5: Rinse
Time to turn the water back on and rinse off. Again, a slow 360° turn makes certain the soap is washed off every part. This time I take about forty seconds, using another two or three quarts of water to bring the total up to a little less than a gallon (not counting the water I saved for dishwashing, of course).
Step 6: Clean up and dry off
I'm a big believer in what I call "minimum-effort housekeeping." That means I do little bits of cleanup as part of my daily routine, so the rig stays pretty clean all the time. Almost never do things get so dirty that I have to take half a day and do a major housecleaning... so housekeeping never feels like a chore, because it's broken up into bite-sized pieces.
After showering, I wipe the excess water off myself and then reach for my "California Dry Blade" silicone rubber squeegee. (Any squeegee will work, but I like this one because it's eleven inches wide, and thus gets the job done faster.) First I wipe down the walls to prevent soap film from building up; then I squeegee the shower curtain. Before I started doing that, the plastic curtain used to get so covered with soap scum that I'd have to run it through the laundromat every month or so to keep it looking decent. No longer! Now it always looks good.
Then I finish the job by drying the walls with a chenille microfiber wash mitt. This incredibly absorbent mitt (available at Wal-Mart or almost any auto parts store) soaks up every bit of remaining moisture, and leaves the shower stall gleaming, as if it just came from the factory. I use the same mitt on my bathroom sink to keep it looking shiny too.
You're probably thinking this all sounds like a lot of work, but it actually doesn't take much more time to do it than to read about it... a minute or two at most. And because I do it daily, my shower always looks great.
Look, no bath mat!
I guess I should mention one other showering tip: I don't use a bath mat. It's just one more thing to store, and one more thing to launder. Instead, I dry my feet before stepping out of the shower. It's easy enough: I hold one end of the bath towel in each hand, so that it hangs down in a "U" shape. Then I put one foot into the "U," scrub the towel back and forth a few times, and my sole is dry. Set that foot on the floor, do the same for the other foot, and presto! No wet footprints, and no need for a mat. In fact, in cold weather, I'll step directly into my slippers. With dry feet, there's no reason not to.
This is such an obvious way to simplify one's life a little... but judging by the number of soggy bath mats I see draped in other people's bathrooms, it doesn't seem to be a widely used technique. You might want to try it. When you're RVing, every little bit of simplification helps!