Boondockers with tankless water heaters, please checkout Shower Miser, it's a 2 way valve that circulates water from shower head back to freshwater tank so water stays hot until your ready for it. It keeps the water temperature constant and doesn't fill grey tank. It does take some work to install but well worth it. It took wife and I about 4 hours to install,and $30. worth of pex pipe and shark bite fittings.
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