And while we're on the HWH issue, another handy mod is installing an on/off switch in the cabin to control the electric heating element
side of the HWH. Here's a cut & paste of my mod that I posted on the Casita forum several years ago.
Adding an interior control switch is a pretty simple conversion to make...
Instructions for Installing a Remote HWH 120 vac Switch, for turning the electrical
element in the HWH on/off from inside the trailer).
A 3 terminal single pole pilot light switch (it has 2 brass screw and 1 silver screw terminals.) Leviton makes one with a switch on top and a red pilot light on the bottom that fits a single electrical rectangular box (see pic below). You can find them at any "big box" store.
* A rectangular single electrical box, specifically designated "for use in old, or existing construction". This model will have a swing-out wing on each side with a screw in each to draw the box up tight to the backside of the bulkhead for mounting.
* A saw, or other cutting device necessary to cut a hole to mount the box, (again, wherever you choose to locate it.) I personally prefer using a Roto-Zip for this, but a drill for pilot holes and a jigsaw with a fine blade will work. If you use a jigsaw, applying some masking tape around the outside edge will help protect the fiberglass or wood damage caused by the vibration when cutting.
* 12/3 w/Ground Romex wire, which will have a Black, White and a Red insulated wire, as well as a bare ground conductor. Allow yourself enough wire to adequately reach your intended location, (wherever you decide to locate it inside your trailer,) and enough extra to carefully route it around the perimeter of any cabinets. I would recommend following and attaching it with zip-ties to the existing wiring bundle running through the trailer to the extent possible. I mounted my switch under the leg area of the side dinette table on the front of the rear bench. (If you choose to mount it there also, then about 6 feet of wire should be sufficient for your installation.)
Unplug your trailer's shore power cord. Then remove the converter's cover plate to expose the 120 vac circuit breakers. Locate the breaker which controls the HWH (should be marked on the cover plate) and remove the black wire from the top terminal screw on this breaker. Pull this wire out of the terminal, but keep it handy.
1.) Using the BLACK wire of the three insulated wires in the new Romex cable, attach it to the HWH breaker terminal screw in the trailer's converter panel, and connect the other end to one of the gold colored screws on the new switch. (It doesn't matter which one, as long as it is one of the gold screws.)
2.) The RED wire is connected to the other gold screw on the switch, and is then wired back to the original black wire that was removed from the breaker terminal, (you remember the one that you removed from the breaker...yes, that one.) So, one wire will be black and the other will be red at this connection, but this is not a problem, nor code violation. Twist them together well with electrician's pliers, then wire nut and seal it real good with electrical tape.
The switch itself needs to have a neutral wire in order for the pilot light to come on when the HWH element is energized.
3.) Use the WHITE wire for that purpose, and it goes on the silver screw on the switch. The other end of the white wire goes to an empty screw on the neutral bus in the main converter panel below the breakers. Be sure it is attached to the neutral bus, not the ground bus (Yes, they are not one and the same.)
To differentiate the two:
* You will see a large white insulated wire attached to a big screw terminal that has a copper bus bar with several screw terminals on it as well. This is the neutral bus.
* The other copper bar with terminal screws is the ground bus, and usually has a large green or bare wire attached to it along with several ground wires.
4.) Connect the BARE ground wire to the ground screw on the new switch and the other end to the ground bus in the converter panel.
When you are done hooking all these connections up, replace the converter's cover plate and install the new switch cover plate. Then turn your converter panel circuit breaker on again, (and don't forget to leave the outside switch located on the HWH itself in the ON position at all times to make it work from inside, because power still goes through this switch on the HWH itself. Its nice to not have to go outside to turn it on or off each time you want hot water.)
Finally, make sure that your new switch is in the OFF position before re-establishing your shore power connection to prevent burning up the heating element (unless you are absolutely sure your HWH is full of water.)
Remember, you now control the electrical side of your HWH solely from this new switch!
It really helps to be able to see at a glance whether the electric power is still on before you risk burning up your heating element, (which would happen in about 1 minute if there isn't any water in the HWH reservoir.)
I mounted mine in the "leg area" under the rear side dinette bench, but the location choice is up to you.
Hope this helps. Write if you have any questions.