Houston Remodeler wrote:

Our 2015 Starcraft TT came with the factory 6 gallon hot water heater (HWH) with the usual "feels like 9 gallons" claim. Y'all know the drill; No washing dishes while showering, Quick showers, spacing the showers to let the HWH make more hot water.... I shopped for factory made RV gas fired on demand HWH and found they run about $1200 and had to be professionally installed. I am too [s]cheap[/s] thrifty to spend two grand for hot water.

Then I had another McGyver moment - why not add our existing Ecco Temp 5 On demand hot water heater to the TT to have endless hot water?

The new install works excellently. Last weekend we hosted 12 people showering (they are in tents) with no want for hot water all weekend. They did have to bring their own towels.

What we did-

1- Install a diverter tee to the stock incoming cold water supply pipe just before the stock HWH. This tee sends the cold water supply either to the on demand or to the stock heater, making the mod reversible.
2- Installed another (regular) tee just after the diverter tee to bring the water back from the on demand. Since the diverter tee will not allow backflow, the second tee doesn't need to be special.
3- Ran pex from the tees to the on demand heater at the rear of the TT, which hangs on the outside ladder, keeping the heater a few inches away from the trailer siding.
4- At the ends of the pipes outside are self shut off, brass, hose style quick connect fittings. These fittings also act as valves, preventing backflow, pipe drainage, and makes the mod reversible.
5- We made jumper hoses from the quick connect fittings to and from the on demand.
6- The on demand uses a typical 20 pound LP (high pressure) tank which also serves our outdoor fire pit. The TT has low pressure LP so we can't use the TT gas to run the on demand.
7- To keep the wind from blowing out the flame* on the on demand and add a rain shield, I installed a typical galvanized, off the shelf from home depot, 4x10" rectangle to 4" round galvanized duct, topped with a class B roof cap. These caps are designed to prevent pilot blow out. Our weekend was very windy and we had zero problems.
8- Dis-assembly is as simple as the quick connects for the 2 water hoses and the LP to the portable tank. We toss the whole thing in the rear storage compartment on the same corner.
9- To keep the fittings on the outside / underside of the TT clean, there is a short jumper hose which replaces the on demand while the TT is in transport or storage. It loops around the nearby bumper to keep it from sagging or pinching.

Counting the heater itself, we spent $286

The on demand is excellent at bringing hose water up to a much higher temperature and acts as a pre-heater to the stock HWH. The factory HWH is excellent at topping off the temperature to nearly scalding, which is how I like my showers. Use of cold water was necessary as we had endless, more-than-hot-enough water to take showers as long and as many as needed. There were times when people were in line using the shower one after another. We washed dishes at the same time. Everyone was happy.

*The Ecco Temp LP HWH's are battery powered, self igniting flame when they sense water flowing. However, when its windy, the flame can be blown out, shutting down the water heating but not the water flow. To restart the flame, either the water needs to be stopped and re-started OR the unit turned off and back on by means of the rocker switch on the bottom of the HWH. Thus the attention to wind is important as you're in the shower nekkid when the unit is running. This usually is a really bad time for the HWH to stop working. The addition of the HVAC adapter and the B vent cap eliminated the fear of the flame being blown out.