Jayco 5th Wheels Questions

We have a Jayco Designer and are very pleased with the build quality, so I'd have no concerns there. Regarding your question related to an 18 gallon equivalent hot water heater, this is likely an Atwood heater with a 10 gallon tank and mixer valve. The water is heated up to a much higher temperature than a standard RV water heater, then mixed with cold at the outlet via a mixer valve to yield hot water at the standard temperature. The result is that you can get the same amount of hot water as that of an 18 gallon tank. We have this on our Designer, and it works very well, having never run out of hot water even when taking back-to-back showers. The only problem we've experienced with this was one time when the mixer valve got clogged with sediment. We replaced the valve with one purchased from Amazon that featured a screen on the inlet. Easy install as it screws directly on to the back of the tank. Don't recall the cost, but I don't recall that it was prohibitive.