I’ve seen this tip or variations of it on several RV forums and blogs over the years. You use a remote oven or BBQ thermometer to keep track of the water heater temperature. The temperature probe is placed against the water heaters metal tank.
Once the temperature reaches your preferred showering comfort zone, you turn off the water heater. Now you can shower using just the hot water faucet with no need to mix hot and cold.
This tip has several benefits:
Saves LP Gas – Since the water is only heated to your lower preferred temp versus the water heater preset temperature less water heater burner time is needed.
Saves Water – Water usually wasted trying to mix hot and cold to a preferred showing temp is saved.
No More Cold Blast – The cold blast of water some RV boondockers experience when they turn off the water to lather up and turn back on to rinse is eliminated.
Flow Control – Smooth control of water flow and volume using the one tap without temperature fluctuation.
Links to similar products as seen in the video (Disclaimer: Amazon Affiliate)