Plumbing Sizing Guide
Sizing your plumbing system comes down to how you use water and how often you can refill. This guide helps you pick the right tank sizes, pump, and water heater for your build.How Much Water Do You Actually Use?
Here’s a realistic breakdown of daily water consumption in a van:| Activity | Water Usage |
|---|---|
| Cooking (meal prep, boiling, cleaning) | 1–2 gallons |
| Drinking | 0.5–1 gallon |
| Dish washing (by hand) | 2–3 gallons |
| Quick shower (Navy style — wet, soap, rinse) | 2–3 gallons |
| Full shower | 5–8 gallons |
| Hand washing (throughout the day) | 0.5–1 gallon |
| Daily total (one person, conservative) | 5–8 gallons |
| Daily total (two people, full use) | 10–15 gallons |
Tank Sizing
Fresh Water Tank
Formula: Daily usage × Days between refills = Minimum tank size| Scenario | Daily Use | Days Between Fills | Minimum Tank |
|---|---|---|---|
| Solo, basic (no shower) | 4–5 gal | 3–4 days | 15–20 gal |
| Solo, full use | 7–8 gal | 3–4 days | 25–30 gal |
| Couple, conservative | 10–12 gal | 3 days | 30–35 gal |
| Couple, full use | 13–15 gal | 3 days | 40–50 gal |
| Tier | Fresh Tank | Notes |
|---|---|---|
| Basic | 15–20 gal | Kitchen sink only, 3–5 day range |
| Standard | 25–35 gal | Kitchen + shower, 3–4 day range for a couple |
| Premium | 35–50+ gal | Full bathroom, extended boondocking capability |
Grey Water Tank
Size your grey tank at 80–100% of your fresh tank capacity. If you have 30 gallons of fresh, run a 25–30 gallon grey tank. Going smaller means your grey fills up before your fresh runs out, which forces you to dump more often.Pump Selection
| Pump Spec | Basic | Standard | Premium |
|---|---|---|---|
| Flow rate | 2–3 GPM | 3–4 GPM | 4–5 GPM |
| Pressure | 30–40 PSI | 40–55 PSI | 45–60 PSI |
| Power draw | ~3A at 12V | ~5A at 12V | ~7A at 12V |
Water Heater Sizing
Tankless (Propane)
- Output: 1.5–2.5 GPM of hot water on demand
- Ignition: Battery or hydro-powered (no pilot light)
- Brands: Camplux, Eccotemp
- Best for: Standard and Premium builds — instant hot water, no tank to keep warm
Tank Heater
- Capacity: 2–6 gallons
- Fuel: Propane, electric, or dual-fuel
- Best for: Builds where you want stored hot water ready to go without waiting
No Hot Water
Basic builds often skip hot water entirely. You can always heat water on the stove for dishes.Line Sizing
| Line | Size | Use |
|---|---|---|
| Main trunk line (pump to manifold) | 1/2” PEX | Main supply |
| Individual fixture runs | 3/8” PEX | Sink, shower connections |
| Grey water drain | 3/4” or 1” flexible | Gravity drain to tank |
Freeze Protection
If you’ll ever be in temperatures below freezing:- Drain system: Install low-point drains so you can completely empty all lines and tanks.
- Insulation: Wrap exposed lines and tanks with pipe insulation. Pay special attention to anything under the van.
- Heat tape (optional): Electric heat tape on exposed under-van lines and tanks. Draws power but prevents freezing.
- Antifreeze option: RV-rated antifreeze can be run through the system for winter storage.
Next Steps
- Water Systems Deep Dive — Detailed look at fresh, grey, and black water
- Plumbing Overview — Full system overview
- Electrical System Sizing — Your pump runs on your electrical system
- Get a custom plumbing quote →