Home / Bathroom and water
Bathroom and water
A compact wet bath, toilet choices, and water-system planning for the 16 × 8 ft draft trailer. Prices are current listings checked 2026-10-11.
Terms
- Wet bath
- One waterproof room. The shower, toilet and floor can all get wet.
- Grey water
- Used water from the sink and shower. It is not toilet waste.
- FRP
- Fiberglass-reinforced plastic. It is a tough, washable wall sheet.
- GPM / BTU / LP
- Gallons per minute (GPM) is water flow. A British thermal unit (BTU) measures heat. Liquid propane (LP) is the fuel in a propane cylinder.
Wet bath
A 24 × 36 in pan is a real small-RV size. Retailers also list 24 × 32, 32 × 32 and 36 × 36 in classes. A 24 × 36 in pan is a tight starting point; draw the actual toilet, elbow room and door swing before buying. RV-pan listings
| Part or wall | Size / weight / drain | Current listing price, 2026-10-11 | Fit and trade-off |
|---|---|---|---|
| RecPro ABS pan | 24 × 36 × 5.25 in; ABS plastic; drain side must match layout source | $191–$302 listing | Compact, light plastic. Weight and drain-hole diameter: no source found. |
| FRP sheet | 4 × 8 ft, 0.09 in thick source | $48/sheet listing | Budget DIY wall. Seal every joint, corner and fastener; panel itself is water-resistant, but seams are the work. |
| One-piece RV surround | Made to match a pan; exact size and weight depend on the model source | $200–$300 surrounds listing | Fewest seams. It needs a wall opening and may be awkward to bring into a finished trailer. |
| Sealed plywood | Custom size; weight and cost depend on plywood and coating | No source found | Can fit curves and odd corners. It only works if every face, edge, screw and seam remains sealed. Do not treat bare plywood as waterproof. |
Put an exhaust fan over or near the shower. Moisture is the reason, not comfort alone. The Home Ventilating Institute calls for at least 50 cubic feet per minute (CFM) in bathrooms at or below 50 sq ft. HVI guide Joe did not build a wet bath; he bought an outdoor shower kit and made an aluminum, flip-up cover for its nylon case. Joe's shower note
Toilet choices
| Type | Size / empty weight | Current listing price, 2026-10-11 | Emptying and needed system |
|---|---|---|---|
| Thetford C224 cassette | 16.75 W × 17.88 D × 28.69 H in; 22.5 lb; 2.37 gal cassette source | $650–$800 listing | Remove the sealed cassette through an exterior service door and empty at a toilet or dump point. No black tank; needs a small flush-water supply. |
| Porta Potti 565E | 15.25 W × 17.75 D × 17.63 H in; 4 gal fresh / 5.5 gal waste source | $185–$189 listing | Carry its lower waste tank to an approved toilet or dump point. No fixed plumbing, black tank or vent. Empty weight: no source found. |
| Nature's Head composting | 19 W × 19 D × 21 H in; 23 lb source | About $985 listing | Empty urine bottle and solids bin separately. Needs the supplied 1.5 in vent hose and a small electric fan; no black tank. |
| Air Head composting | 18.75 W × 19 D × 19.75 H; 5 gal solids bin source | $1,095 listing | Separate and empty liquid and solids containers. It needs a vent; empty weight: no source found. |
| Dometic 310 gravity toilet | 15 W × 20 D × 19.6 H in; 10 in rough-in source | $285 listing | Flushes to a plumbed black tank. That tank needs a vent and a 3 in dump-valve system; toilet weight: no source found. |
Claude's starting pick: a Porta Potti is the low-cost, removable first step. A cassette is neater but needs an exterior hatch. A gravity toilet adds a black tank, vent and dump plumbing. Pick after the bath location is fixed.
Fresh and grey water
| Part | Useful sourced examples | Install note |
|---|---|---|
| Fresh tank | Class A Customs lists 20 gal at 32.5 × 11.75 × 11.75 in and 21 gal at 34 × 9 × 16 in; 20 gal tank shipping weight is 13 lb. source | 20–30 gal is the useful range here. Full water weighs 8.34 lb/gal, so 20 gal adds 167 lb. USGS |
| Grey tank | An under-floor 20 gal example is 48 × 13 × 8.5 in; its listed shipping weight is 30 lb. listing | Use 10–30 gal only after measuring between frame rails. Support the whole tank with structure; do not hang it from plumbing. A 1.5 in grey drain valve is common; source found only in an industry forum, so verify the chosen tank's outlet. discussion |
| 12 V pump | Shurflo 4008 class: 3.0 GPM, 55 pounds per square inch (PSI), 7.5 A maximum; use a 10 A circuit. manual | Mount near the fresh tank with a strainer. It draws battery power only while pumping. |
| City water and winter drain | A regulator example holds 45–50 PSI. listing | Add a city-water inlet, check valve, regulator and a low-point drain. A winterizing procedure/source for this exact DIY system: no source found. |
At Texas state parks, wastewater, including grey water, may be discharged only at designated dump stations. Do not dump it on the ground. Texas Parks and Wildlife rule A broader Texas rule for this trailer's hunting lease: no source found.
Hot water
Tankless heaters save stored-water weight but cost much more. Both types need the maker's exterior door/vent, LP plumbing and a carbon-monoxide (CO) alarm; CO is a poisonous combustion gas. Do not substitute a wall cutout or vent size from another model.
| Heater | Size / weight / output / 12 V | Current listing price, 2026-10-11 | Opening and vent |
|---|---|---|---|
| Girard GSWH-2 tankless | 12.5 W × 12.5 H × 15.5 D in; 24 lb shipping; 42,000 BTU; under 3 A listing | $850–$900 listing | Use its specified exterior door/vent; it fits a tank-heater cutout. maker |
| Furrion tankless | 2.4 GPM; 60,000 BTU; 16.14 × 16.14 in door maker | From $786 listing | Maker-supplied door is the outside combustion vent. Weight and 12 V draw: no source found. |
| Suburban SW6D, 6 gal LP tank | 12.7 W × 12.7 H × 19.2 D in; 35 lb dry; 12,000 BTU listing | About $550 listing | 12.75 × 12.75 × 19.2 in cutout; exterior door is its vent. 12 V amp draw: no source found. |
| Atwood 6 gal LP tank | 16 W × 12.5 H × 20.88 D in; 19 lb empty; 8,800 BTU listing | Price: no current source found | Use its maker door and outside vent. 12 V amp draw: no source found. |
A low-flow shower head at 1.5 GPM uses 4.5 gal in a 3-minute shower. That is flow × time, not a promise of comfort. 1.5 GPM listing
Water use for 3 days off-grid, 2 people
| Use | Fresh gal | Grey gal | Basis |
|---|---|---|---|
| Three short showers total | 13.5 | 13.5 | 3 showers × 3 min × 1.5 GPM flow source |
| Drinking and cooking | 6 | 0 | 1 gal/person/day planning allowance; no source found. |
| Handwashing and dishes | 9 | 9 | 1.5 gal/person/day planning allowance; no source found. |
| Total before toilet | 28.5 | 22.5 | Round up for uncertainty. |
| Toilet | Varies | 0 | Porta Potti/cassette fresh flush water is separate; a gravity toilet adds black-tank waste. |
Design numbers for my trailer
| Item | Number | Source |
|---|---|---|
| Wet-bath starting footprint | 24 × 36 in pan | Real RV pan size source |
| Bathroom ventilation | At least 50 CFM | Small-bath guidance source |
| Fresh / grey tank planning | 30 / 30 gal | 3-day table, plus reserve; final tank shape must fit the rails. |
| Full 30 gal water load | 250 lb | 30 × 8.34 lb/gal source |
| Pump | 3.0 GPM, 7.5 A max | Shurflo 4008 class source |
| Budget toilet starting point | Porta Potti 565E, $185–$189 | Removable and no black tank source |
| Hot-water starting point | None selected | Tankless and tank heaters both strain the budget; choose only after LP layout and cutout are final. |