How Does Plumbing Work in a Tiny House?

Dreaming of downsizing but worried about how basic needs like running water and waste disposal will work? You’re not alone. How does plumbing work in a tiny house is one of the most common—and crucial—questions future tiny homeowners ask. Unlike traditional homes, tiny houses demand smart, space-saving solutions that balance functionality, sustainability, and compliance with local codes. In this guide, we’ll break down exactly how tiny house plumbing operates, whether you’re parked on-grid or living completely off the grid.

What Are the Core Components of Tiny House Plumbing?

Every plumbing system—big or small—relies on three essential elements: freshwater supply, wastewater removal, and venting. In a tiny house, these components are miniaturized but must still meet health and safety standards.

• Freshwater system: Delivers clean water to sinks, showers, and sometimes toilets.
• Greywater system: Carries used water from sinks and showers (not toilets).
• Blackwater system: Handles toilet waste (if a flush toilet is used).
• Vent stack: Allows sewer gases to escape and maintains proper pressure in pipes.

According to the Tiny Home Industry Association (THIA), over 68% of tiny homes use hybrid plumbing systems that combine on-grid and off-grid features for flexibility.

On-Grid vs. Off-Grid Plumbing: Which Is Right for You?

Your lifestyle and location heavily influence your plumbing setup. Let’s compare the two most common approaches:

💡 Pro Tip: Many tiny homeowners start on-grid for simplicity, then transition off-grid as they gain experience.

For more on sustainable water systems, see Wikipedia’s overview of rainwater harvesting —a common off-grid solution.

How Is Fresh Water Supplied in a Tiny House?

Tiny houses typically use one of three freshwater sources:

1. City Water Hookup
   If parked in an RV park or on private land with utilities, you can connect directly to a municipal line using a standard garden hose (½-inch diameter) and a pressure regulator (set to 40–60 PSI to avoid pipe damage).
2. Freshwater Tank
   Most mobile tiny homes include a built-in freshwater tank (usually 20–50 gallons). Water is pumped through a 12V DC pump (like the Shurflo 4008) at 3–5 gallons per minute (GPM) to faucets and showers.
3. Rainwater Collection
   In off-grid setups, rainwater is collected from the roof into food-grade barrels (55–100 gallons), filtered through a multi-stage system (sediment + carbon + UV), and stored for non-potable or potable use (with proper treatment).

📊 Case Study: A 2022 survey by Tiny House Expedition found that 42% of full-time tiny dwellers rely on freshwater tanks, refilled every 3–5 days for a single occupant.

What About Wastewater? Greywater vs. Blackwater

Greywater System

Greywater comes from sinks, showers, and washing machines. In tiny houses, it’s often:

• Stored in a greywater tank (25–40 gallons) and emptied at RV dump stations.
• Filtered and reused for irrigation (where legal)—using gravel beds or mulch basins.
• Never mixed with blackwater to avoid contamination.

Blackwater System

Options depend on toilet type:

• Composting Toilets (e.g., Nature’s Head, Separett):
  • No water needed.
  • Solids and liquids are separated; solids compost over time.
  • Emptied every 4–8 weeks (for 1–2 people).
  • Most popular choice—used in 76% of off-grid tiny homes (THIA, 2023).
• Cassette or RV-Style Flush Toilets:
  • Use 0.5–1 gallon per flush.
  • Require a blackwater tank (10–20 gallons).
  • Must be emptied at designated dump stations.

⚠️ Note: Always check local regulations—some counties prohibit greywater reuse or composting toilets.

Space-Saving Plumbing Fixtures & Layout Tips

Tiny house plumbing thrives on efficiency. Here’s how designers maximize every inch:

• Tankless Water Heaters:
  On-demand units (like the Eccotemp L5) heat water instantly, saving space and energy. They use 0.5–2 GPM and require a 120V or propane connection.
• Compact Fixtures:
  • Wall-mounted sinks (12” wide)
  • Corner showers with sliding doors
  • Kitchen faucets with pull-down sprayers (dual function)
• PEX Piping:
  Flexible, freeze-resistant PEX tubing (½-inch diameter) is easier to install than copper in tight walls and reduces heat loss.
• Vertical Stacking:
  Place the kitchen sink directly above the shower drain to share a single greywater line—cutting pipe length by up to 30%.

Step-by-Step: Installing Basic Tiny House Plumbing

If you’re DIY-ing your system, follow these steps:

1. Plan Your Layout
   Sketch fixture locations. Keep hot/cold lines parallel and minimize bends.
2. Install Freshwater Tank & Pump
   Mount tank underfloor or in a storage bay. Connect to a 12V pump with an accumulator tank to reduce cycling.
3. Run PEX Lines
   Use crimp rings and a PEX tool. Insulate pipes in cold climates (R-3 foam sleeves).
4. Set Up Drain-Waste-Vent (DWV)
   Use 1.5” pipes for sinks, 2” for showers. Slope drains at ¼” per foot toward tanks.
5. Vent the System
   Install a roof vent or use an air admittance valve (AAV) like Studor Mini-Vent if roof access is limited.
6. Test for Leaks
   Pressurize freshwater lines to 60 PSI for 15 minutes. Check all joints.

🔧 Tool Tip: A $20 PEX crimping kit from Harbor Freight works well for beginners.

Common Mistakes to Avoid

• Undersizing tanks: A 20-gallon freshwater tank lasts just 2 days for two people showering daily.
• Ignoring freeze protection: In cold climates, install heat tape or drain systems in winter.
• Poor venting: Causes slow drains and sewer smells—never skip this step.
• Using non-potable hoses: Always use “RV-grade” or “drinking water safe” hoses to avoid chemical leaching.

FAQ: Tiny House Plumbing Questions Answered

Q1: Can I use a regular toilet in a tiny house?

A: Technically yes, but it’s impractical. Standard toilets use 1.6+ gallons per flush and require large blackwater tanks. Most tiny homeowners opt for composting or incinerating toilets to save water and space.

Q2: How often do I need to empty greywater tanks?

A: For one person, a 30-gallon tank lasts 4–6 days with conservative water use (e.g., 2-minute Navy showers). Two people may need to dump every 2–3 days.

Q3: Is tiny house plumbing legal everywhere?

A: Regulations vary by state and county. Some areas classify tiny houses as RVs (allowing standard RV hookups), while others require full residential plumbing permits. Always consult your local building department.

Q4: Can I connect my tiny house to a septic system?

A: Yes—if it’s permanently sited and meets local code. However, most mobile tiny homes avoid this due to installation costs ($3,000–$10,000) and immobility.

Q5: How much does tiny house plumbing cost?

A: DIY systems range from $500 (basic off-grid) to $2,500 (full on-grid with tankless heater). Professional installation can cost $4,000+.

Q6: Do composting toilets smell?

A: Not when maintained properly. They use ventilation fans and peat moss/coconut coir to neutralize odors. Users report they smell less than traditional toilets.

Conclusion

Understanding how plumbing works in a tiny house empowers you to design a system that’s efficient, eco-friendly, and tailored to your lifestyle—whether you’re parked downtown or off in the woods. From space-saving fixtures to smart water management, every component plays a role in making small-space living comfortable and sustainable.

If you found this guide helpful, share it with fellow tiny house enthusiasts on Pinterest, Facebook, or Reddit! Got questions? Drop them in the comments—we love helping the tiny home community thrive. 🌱💧