The majority of the plumbing and electrical in the tiny home is routed through the floor cavity. The loci for all of the systems exists at the kitchen-end of the tiny home, near the trailer hitch. There are three critical MEP hubs in this area: A) an externally concentrated cluster on the trailer hitch, where the municipal connections for water and electricity, the instant hot water heater, and the interchangeable propane tanks for kitchen appliances all exist, B) the electrical breaker box in the kitchen wall at the end of the house, which is adjacent to the mini-split unit, and C) the in-floor compartment under the kitchen floor where the solar electric battery bank and on-board water storage exist.
When we designed the trailer for our tiny home, we had the structural tubing framed 12 inches below the top of trailer to allocate for a deeper floor cavity where the solar electric battery bank and on-board water storage tanks could be stored for easy access. The total depth of the cavity is 18", with 9.25" clear under the 2"x10" floor joists.
While having these systems integrated into the enclosure of the tiny home was inconvenient, as they ate up valuable floor storage space, added considerable weight to the home, and made the trailer construction more costly, it was critical to house them within the enclosed, temperature-controlled portion of the home. Concerning the battery bank: if stored without temperature regulation, high temperatures can shorten battery life, while low temperatures can reduce battery capacity. Concerning the on-board water storage: in an off-grid water supply system (and especially in the case of a tiny home on wheels), great care should be taken to make sure that water pipes do not freeze in the winter. If your rain water catchment storage is outside of the home, above ground, and not insulated, then you would need to disconnect your pipes from your water supply in freezing temperature situations. For this reason, we planned to always have 90 gallons of water (enough for two people for one week) on-board in our tiny home, so that in the event of freezing temperatures we could still access water in the short-term.
In any given building project, it is best to optimize plumbing by clustering functions together, which minimizes linear feet of plumbing lines, minimizing not only cost, but also the potential for leaks. We sacrificed optimized plumbing in our own tiny home for our preferred floor plan configuration. However, we still managed to cluster plumbing into two 'zones' at either end of the house: kitchen/on-board water storage at one end and bathroom/washer at the other.
After the plumbing was entirely routed through the floor cavities at the perimeter of the home, we were able to insulate and fully sheath the fixed portion of the floor. The rest was left open and accessible for general in-floor storage.
"The Plumbing Leak Saga" as it has become known, was an approximately 6-week period, during which a small, yet persistent leak in the plumbing system plagued Kadim day and night. He would daily adjust some component of the system, reset the pressure gauge, come back the next day, and do it all over again, until through process of elimination he located and eradicated it! It was a very trying time; don't ask him about it unless you want an ear-full!
As demonstrated in the above images, most of the electrical was run on a datum above the doors and windows. This allowed for efficient and uninterrupted routing throughout the tiny home: at sleeping loft outlets, in the bathroom for outlets, lighting, and the ceiling vent, in the utility closet for the washer, periodically in the living area, in the main ceiling for the downlights, at the kitchen counter for small appliances, under the kitchen counter for large appliances, at the solar batter bank, and above the kitchen window for the mini-split unit. These pictures don't show it, but we did install metal plate covers on the studs where electrical wires were routed to prevent any future accidental penetration of the wires when installing interior and exterior wall sheathing or finishes.