Here are a couple simple mods we did to our Jayco. Each took less then a half hour to perform.
We boondock mostly and with 2 kids have the potential of going through a ton of water quickly. The first thing we did was to replace the shower with a sink sprayer. Works great for NAVY showers. Get in, get wet, scrub up, rinse off.
For some reason water always puddled and ran down the sides of the tube so I got some of that plastic wall corner protector and cut it down to size, and filed away the corners and siliconed it to the tub.
Here is a water pump noise muffler. It's made out of sound board, so it's a little hard to work with, but not impossible. it gets the pump off the floor, and encloses it. We also put noddles around all the pipes that made contact with the walls and floor. It reduced the sound significantly.
Our trailer came with a cabnet door that was screwed in place, behind it was the hot water heater. I installed hinges and a door catch. Simple and it gave us a little space to store small things.
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Have Fun,
2007 Jayco JayFeather 20BH
2009 Ford F150 5.4L