3 Minute Showers

Get an oxygenics shower head and use less water and your shower will last longer...

I see no reason to waste water, electricity, propane and sewer capacity. There is no problem other than wasted resources.

Yes, in theory a demand WH would work but there have been lots of performance issues with them in RV's. Some have been happy with them though.
Do lots of research before you buy one!
Maybe someone here can suggest a model that worked well for them?

Why not solve the problem by simply gutting that heavy, inefficient tank water heater and install an on-demand unit? Maybe it's just me, but it sounds like the logical way to go. Sure, it will cost you some $$$ at the outset, but if you only use propane when you need hot water, don't have to worry about replacing an anode rod, don't have to reheat water/keep water hot that is in the tank, you'll eventually save back what you spent for the unit.

turn on both elec. & propane water heating. It''ll help some on water heating and recovery.
Check your propane only heat temp, elec. only heat temp. A cooking thermometer in a glass of heated water may show the thermostats are set too low.
120 F is optimal, legal commercial. You may set your temp higher on your ' cold' water heater to give you longer showers.
Elec. water heating is notoriously slow and 'cool ' used alone. By law, they are set at a max.of 120f. 6 gal. just cant do what you want at that temp. and slow 10 Amp 10360 btu recovery rate.
An option for you is
Burn Propane, its 30,000 btu heat rate. set your propane regulator thermostat higher. you will get the hot water for what you wish. Educate all your family that it is very hot, to be careful of scalding.

IF you are connected to AC Power Source then turn on the electric and the propane at same time.

That 6 gallon will heat to 130*F -----electric/propane shut off
Then turn back on when water temp drops to 110*F

How long you get hot water is dependent on how HOT of a shower you take.
130*F will scalded within just a few seconds so you are not using straight hot water.....using it tempered with cold

Residential shower avg temp is 105*F, lasts 8 minutes and uses 40 gallons of water
You are NOT going to get that with your RV water heater

BUT you can take a long warm shower for several minutes and extend the supply of hot by using electric/propane and NOT letting shower run the whole time you are in the stall.

That Suburban WH is rated at 20 gallons per hour recovery rate using both heat sources

If you run gas and electric at the same time, you will have faster recovery. It could be that there is too much water flow, if restrictor is removed from shower head. One other problem, water supply colder than normal.

Jerry

Your water heater should get much hotter than that, and it probably is. Most of the time, when water is warm, but not hot, it's because it's getting mixed with cold water somewhere in the lines. How does this happen? It happens to a lot of us until we learn.

Check all your faucet handles and make sure they are turned off, especially showers and outside showers where hot and cold come out together.

If you have an outside shower and have the shower head turned off, but the faucet handles till on, water will mix hot and cold and feed back luke warm through your system, making everything just warm, never hot.

This is the first thing to check. Check ALL faucets and make sure ALL are off, not just off at a shower head. 99.9% of the time .... THIS is the problem.

Get a hotel room and use all you want to. Then go dirty for a few days till you get ready for another long soak.

If that model runs on gas and electric, it helps if you run both modes at the same time. Or you may already know this.