One suggestion if replacing the element in an RV water heater may sound strange but read on... The Element is nothing more than a resistor so it's not all that concerned about voltage.. It's more concerned about current (Too much and it's history)
So get an element rated for 1500 watts at 240 volts..
What happens if you do this.
Now I know some RV's are only 1400 watts but 1500 watts at 120 volts is 12.5 amps That's a "Big Load" 1400 is 11 2/3 still a big load
But that 240 volt 1500 watt.. When you cut the voltage in half you will also cut the current since I=E/R so you get 6.25 amps That's a medium load. and 385 watts.. Takes a bit longer to hot up the water but the temp is controlled by something else (Thermostat) so it will hold it at 120 just fine.
And on a 30 amp site...MORE amps left over for other stuff.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times