Category: 🚰 Plumbing & Water System

Tanks, pumps, plumbing diagrams, fixtures, etc.

Save a Drop P3 Water Flow Meter – Fresh Water Fill Monitoring

Save a Drop P3 Water Flow Meter – Fresh Water Fill Monitoring

As part of planning the fresh water system for this cargo trailer conversion, I wanted a simple way to
monitor how much water is going into the tanks during fills.
A small inline flow meter on the hose is an easy, low‑tech way to track gallons used and avoid overfilling.

One product I’m considering for this purpose is:


Save a Drop P3 Blue Water Flow Meter – Measure Gallon Usage from an Outdoor Garden Hose

Product Overview

The Save a Drop P3 is a compact, inline water flow meter that attaches to a standard garden hose.
It measures the total volume of water passing through and displays usage in gallons, making it useful for
filling RV or trailer fresh water tanks, portable containers, or even just tracking water consumption.

  • Type: Inline water flow meter
  • Connection: Standard garden hose
  • Display: Digital readout of gallons used
  • Use Case: Monitoring tank fills and conserving water

Why This Is Useful for the Build

When filling fresh water tanks, it’s easy to lose track of how much water has gone in—especially when filling from
portable containers or non‑metered sources.
A small flow meter like this provides:

  • Overfill awareness: Know how many gallons have gone into the tank before it reaches capacity.
  • Repeatable fills: Easy to track partial fills (e.g., “add 10 gallons” instead of “fill until it overflows”).
  • Water usage insight: Helps understand how quickly water is consumed during trips.
  • Portable and flexible: Can be used on any hose, not permanently installed.

How It Fits Into the Fresh Water Workflow

In practice, this meter would be attached inline on the hose used to fill the fresh water tank(s).
Before starting a fill, the meter can be reset to zero, and the display will show the total gallons added during that session.

  • Attach meter between spigot and hose, or hose and tank fill.
  • Reset meter before each fill.
  • Monitor gallons as the tank fills to avoid overfilling.
  • Optionally log usage to better understand daily water consumption.

This page serves as a reference for a simple, portable tool that can make tank filling more controlled and predictable,
especially when working with multiple tanks or off‑grid water sources.

Updated Diagram – Urine Separator, Sink Drain, Sump Pump, and Gray Tank System

Updated Diagram – Urine Separator, Sink Drain, Sump Pump, and Gray Tank System

This diagram shows the updated plumbing layout for the bathroom: the composting toilet’s urine separator and the bathroom sink both drain into the sump pump box.
The sump pump then sends all liquids to the interior gray tank, with a check valve placed before the gray tank to prevent any backflow.
The toilet sits elevated above the sump pump by at least one foot, ensuring reliable gravity flow.

System Diagram (Top‑Down Flow)


                 ┌───────────────────────────────┐
                 │     COMPOSTING TOILET         │
                 │   (Urine Separator Outlet)    │
                 └──────────────┬────────────────┘
                                │
                                │  Gravity-fed Urine Line
                                ▼
                 ┌───────────────────────────────┐
                 │       BATHROOM SINK           │
                 │  (Drain Tied Into Urine Line) │
                 └──────────────┬────────────────┘
                                │
                                ▼
                 ┌───────────────────────────────┐
                 │   COMBINED DRAIN LINE (1")    │
                 │  Sink + Urine to Sump Pump    │
                 └──────────────┬────────────────┘
                                │
                                ▼
                 ┌───────────────────────────────┐
                 │     SUMP PUMP BOX (12V)       │
                 │  - Collects shower water      │
                 │  - Collects urine + sink      │
                 │  - Auto pump activation       │
                 └──────────────┬────────────────┘
                                │ Pressurized Output
                                ▼
                 ┌───────────────────────────────┐
                 │         CHECK VALVE           │
                 │  (Prevents backflow from tank)│
                 └──────────────┬────────────────┘
                                │
                                ▼
                 ┌───────────────────────────────┐
                 │       INTERIOR GRAY TANK      │
                 │  - Receives all pumped liquid │
                 └───────────────────────────────┘

Side‑View Height Relationship


   [Composting Toilet]
            │
            │  (Urine Line)
            ▼
   [Sink Drain Tie-In]
            │
            ▼
   (Combined Drain Line)
            │
            ▼
   [Raised Shower Platform]───────────────┐
            │                              │
            ▼                              │
      [Sump Pump Box]  <───────────────────┘
            │   (Pumps upward)
            ▼
      [Check Valve]
            │
            ▼
      [Interior Gray Tank]

This layout ensures the toilet and sink both drain by gravity into the sump pump, while the sump pump handles all elevation changes needed to reach the gray tank.

Why the Sink Tie‑In Helps

Tying the bathroom sink into the urine line provides several benefits:

  • Flushes the urine line with clean water every time the sink is used.
  • Prevents salt buildup or odor in the urine hose.
  • Adds enough liquid volume to reliably trigger the sump pump float switch.
  • Reduces plumbing complexity by combining two low‑flow drains into one line.

Why the Check Valve Belongs Before the Gray Tank

Placing the check valve on the pressurized discharge line (not the urine line) ensures:

  • No gray water can flow backward into the sump pump box.
  • No contamination risk for the toilet or sink drain lines.
  • The sump pump remains protected from tank pressure or sloshing.

This updated diagram reflects the final intended flow path for the bathroom plumbing system and will be used as part of the full interior‑only plumbing documentation.

Build Notes – Floor, Insulation, and Bathroom Plumbing

Build Notes & Lessons Learned – Floor, Insulation, and Bathroom Plumbing

As I continue refining the design for the cargo trailer conversion, I’m collecting important details that will influence how the trailer is ordered and how the interior systems are built.
These notes focus on floor structure, insulation planning, and bathroom plumbing considerations based on research and reference videos.

No Dovetail for a Level Interior Floor

For this build, a flat, level floor is essential. This means the trailer must be ordered with no dovetail.
A dovetail is the angled drop at the rear of many cargo trailers, designed for loading low vehicles.
While useful for ramps, it creates an uneven interior floor and complicates cabinetry, flooring, and bathroom layout.

Choosing a non-dovetail rear ensures:

  • A fully level floor from front to back
  • Simpler installation of flooring, insulation, and cabinetry
  • Better support for the raised shower platform and tank placement

Interior Doors Must Be Raised for Floor Insulation

If the trailer does not come factory-insulated, the interior floor will be built up with insulation and subfloor layers.
This adds approximately 1.5 inches of height to the finished floor.

To avoid clearance issues:

  • Interior doors (bathroom, bedroom, etc.) must be raised at least 1.5″ during installation.
  • Dealers should not install interior trim — trim should be left loose inside the trailer.

This prevents the door from dragging on the finished floor and allows trim to be installed after insulation and flooring are complete.

Backer Boards Before Insulation (Video Reference)

In this video (timestamp 2:15):

Cargo Trailer Conversion – Insulation Prep

The creator explains the purpose of installing backer boards before adding insulation.
These boards provide:

  • A solid mounting surface for walls and fixtures
  • Structural support for areas where screws cannot bite into foam
  • Better rigidity and long-term durability

This reinforces the plan to include backer boards in key areas before insulating the walls and ceiling.

Urine Separator Plumbing Into Sump Pump (Video Reference)

In this video (timestamp 27:50):

Cargo Trailer Bathroom Plumbing – Urine Separator & Sump Pump

The builder demonstrates how the urine separator line from a composting toilet can be routed into the same shower sump pump box that feeds the gray tank.
This setup includes:

  • A dedicated urine drain line entering the sump box
  • A check valve to prevent backflow from the gray tank
  • Automatic pumping of both shower water and urine into the gray tank

This is a useful reference for integrating the composting toilet’s liquid output into the interior gray tank system without needing a separate container.

Summary

These notes help shape several key decisions for the build:

  • Order the trailer without a dovetail for a level interior floor.
  • Ensure interior doors are raised 1.5″ if insulating the floor after delivery.
  • Use backer boards before insulation for structural support.
  • Consider routing the urine separator into the sump pump with a check valve.

These insights will be incorporated into the final layout and construction plan as the build progresses.

Raised Shower Drain System – Diagram & Flow Path

Raised Shower Drain System – Diagram & Flow Path

This diagram illustrates how the raised shower platform, low‑profile drain, 12V sump pump box, and interior gray tanks work together as a complete drainage system.
The goal of this design is to keep all tanks inside the trailer, avoid any under‑floor tank mounting, and ensure reliable drainage even when the gray tanks sit higher than the shower pan.

System Overview Diagram

                 ┌───────────────────────────────┐
                 │       RAISED SHOWER PAN       │
                 │   (Built on framed platform)  │
                 └──────────────┬────────────────┘
                                │
                                ▼
                 ┌───────────────────────────────┐
                 │  LOW-PROFILE SHOWER DRAIN     │
                 │   (Scandvik 1" Outlet)        │
                 └──────────────┬────────────────┘
                                │ 1" Drain Line
                                ▼
                 ┌───────────────────────────────┐
                 │   12V SHOWER SUMP PUMP BOX    │
                 │   (Zuomeng 750 GPH)           │
                 │ - Collects shower water       │
                 │ - Auto pump activation        │
                 │ - 3/4", 1", 1-1/8" outlets    │
                 └──────────────┬────────────────┘
                                │ Pressurized Output
                                ▼
                 ┌───────────────────────────────┐
                 │     INTERIOR GRAY TANK(S)     │
                 │  (Mounted inside utility bay) │
                 │ - No exterior tanks            │
                 │ - Freeze-protected             │
                 └───────────────────────────────┘

Flow Path Explanation

The raised shower system works by elevating the shower pan enough to allow a drain line to flow into a compact sump pump box.
The sump pump then automatically transfers water into the interior gray tanks.

  • 1. Raised Shower Platform: Provides vertical space for the drain and plumbing beneath the pan.
  • 2. Low-Profile Drain: Minimizes height while allowing a 1″ outlet to feed the sump box.
  • 3. Sump Pump Box: Collects water and pumps it upward or horizontally to the gray tanks.
  • 4. Interior Gray Tanks: Store all wastewater inside the insulated trailer envelope.

Why This System Works for an Interior-Only Plumbing Layout

This configuration supports the goal of keeping all plumbing and tanks inside the trailer, avoiding exposure to road debris, freezing temperatures, and under‑frame clearance issues.

  • No exterior tanks: All tanks remain inside the conditioned space.
  • Freeze protection: Interior placement prevents winterization issues.
  • Flexible routing: Pumped discharge allows tanks to sit higher than the shower.
  • Compact footprint: Marine components are designed for tight spaces.

Component Placement Diagram (Top‑Down Layout)

 ┌─────────────────────────────── Trailer Bathroom ───────────────────────────────┐
 │                                                                                │
 │   [ Raised Shower ]                                                            │
 │        │                                                                        │
 │        ▼                                                                        │
 │   [ Low-Profile Drain ]                                                         │
 │        │                                                                        │
 │        ▼                                                                        │
 │   [ Sump Pump Box ]  →→→→→→→→→→→→→→→→→→→→→→  [ Interior Gray Tank(s) ]          │
 │                                                                                │
 └────────────────────────────────────────────────────────────────────────────────┘

Notes for Final Design

  • Confirm sump box placement for easy access to the lid and pump.
  • Plan for a service hatch or removable panel in the shower platform.
  • Use smooth‑bore hose for the pump discharge to reduce backpressure.
  • Ensure gray tank inlet height matches the sump pump’s lift capability.

This diagram will serve as a reference as the bathroom plumbing system is finalized and integrated into the overall trailer layout.

Shower Drain Components Under Consideration for the Bathroom Build

Shower Drain Components Under Consideration for the Bathroom Build

As I plan the raised shower platform for the bathroom, I am exploring different components that will allow the shower to drain directly into the interior gray tanks.
Keeping all tanks inside the trailer is a priority for freeze protection, maintenance access, and overall system reliability.
Two products that may play a role in this design are a low-profile shower drain and a compact 12V shower sump pump box.

Scandvik Low Profile Drain Stopper – 1″ Outlet


Scandvik Low Profile Drain Stopper – 1″ Outlet

This drain is designed for marine environments where space is limited and drainage must be routed through tight areas.
Its low-profile design makes it a strong candidate for a raised shower floor where vertical clearance is limited.

  • Outlet Size: 1 inch
  • Design: Low-profile for tight installations
  • Intended Use: Marine showers and wet areas
  • Potential Benefit: Allows the shower pan to sit lower while still routing water into a sump box

This drain could be mounted directly into the raised shower platform, feeding into a sump pump box located beneath or adjacent to the shower structure.

Zuomeng 12V Automatic Shower Sump Pump Box – 750 GPH


Zuomeng 12V Automatic Shower Sump Pump Box – 750 GPH

This sump pump box is designed for boats and RVs to collect shower water and automatically pump it to a gray tank.
For a cargo trailer conversion with interior tanks, this type of system allows the shower to drain efficiently even when the gray tanks sit higher than the shower pan.

  • Brand: Zuomeng
  • Flow Rate: 750 GPH
  • Power: 12V DC (corded electric)
  • Material: ABS housing
  • Maximum Lifting Height: 10 feet
  • Item Weight: 4.64 lbs (2.11 kg)
  • Package Dimensions: 12.05″ × 10.55″ × 5.67″
  • Model Number: HY-056
  • Included Adapters: 3/4″, 1″, and 1-1/8″ hose fittings

The sump box collects water from the shower drain and automatically pumps it into the gray tanks, making it ideal for raised shower platforms or installations where gravity drainage is not possible.

How These Components Fit Into the Shower Design

The raised shower platform will allow the drain to sit above the sump box, which then pumps water into the interior gray tanks.
This approach eliminates the need for any tanks mounted under the trailer and keeps all plumbing inside the insulated envelope.

  • Low-profile drain: Minimizes height while providing a clean outlet into the sump box.
  • Sump pump box: Automatically moves water to the gray tanks regardless of tank height.
  • Interior-only plumbing: Improves freeze protection and simplifies maintenance.

These components are being documented here as part of the ongoing evaluation process for the bathroom plumbing system.
Final selections will be made once the shower platform height, tank placement, and plumbing layout are fully defined.

Black Water Tank Install

Cargo Trailer Camper Conversion – Black Water Tank Install

As part of researching different plumbing layouts for this build, I found a helpful reference video titled
“Cargo Trailer Camper Conversion – Black Water Tank Install” by Be Free Builds.
This video walks through the process of mounting a black water tank under a cargo trailer and adding the basic plumbing components needed for a toilet installation.

You can watch the video here:

Cargo Trailer Camper Conversion – Black Water Tank Install

Black Tank Installation on Custom Cargo Trailer Camper Toy Hauler RV DIY Van Conversion Bathroom

What the Video Covers

The creator demonstrates the full installation process for an under‑mounted black water tank, including:

  • Tank positioning between the trailer frame rails
  • Mounting method using metal straps and wood blocking
  • Cutting openings for the toilet inlet and drain fittings
  • Basic plumbing connections for the toilet and venting
  • Securing the tank to prevent movement during travel

The video provides a good visual reference for how a black tank can be mounted beneath a cargo trailer, especially for DIY conversions where space is limited.

Key Takeaways

  • Frame spacing matters: The tank must fit cleanly between the frame rails without interfering with crossmembers.
  • Strap protection is important: Several commenters note the need for rubber padding between metal straps and the tank to prevent wear over time.
  • Vent routing: The video shows the tank installation but does not go in-depth on vent placement; this is something to plan carefully.
  • Ground clearance: The tank sits below the floor line, so clearance must be considered to avoid bottoming out.
  • Wood vs. metal bracing: Some viewers recommend replacing wood blocks with steel for long-term durability.

Why This Video Is Useful for My Build

Even though my build will not use a black water tank (composting toilet), this video is still valuable for understanding:

  • How tanks are mounted under a cargo trailer
  • How plumbing penetrations are cut and sealed
  • How much space tanks require beneath the floor
  • What to avoid (sharp edges, unsupported weight, low clearance)

This reference helps inform decisions for my fresh water and grey water tank installations, as well as general under‑frame routing and protection.

Additional Notes

The comments section includes useful feedback from other builders, including suggestions for:

  • Using rubber padding or tire rubber between straps and tank
  • Upgrading to steel bracing instead of wood
  • Ensuring proper venting through the wall or roof
  • Checking tank clearance when fully filled

As I continue planning the plumbing system for this build, I’ll reference this video for mounting ideas, strap design, and under‑frame layout considerations.

Rethinking the Nature’s Head: My Composting Toilet Deep Dive

Rethinking the Nature’s Head: My Composting Toilet Deep Dive

When I first started planning this build, the toilet decision felt “done.” I picked the Nature’s Head, dropped it into the plans, and moved on.
It’s a proven, popular composting toilet with a solid track record, and it slotted neatly into the bathroom layout without much debate.

But as this project has evolved, so has my thinking. Today was one of those days where I went down a deep rabbit hole on composting toilets—especially the DIY side—and came back up seriously questioning whether a $1,000+ commercial unit still makes sense for this build.

What a Composting Toilet Really Is

The more I read, the more I realized how simple the core system really is. Strip away the marketing and molded housings, and a composting toilet is basically:

  • A solids container for the composting material and waste
  • A liquids diverter to keep urine separate
  • A small ventilation system to move air and control odor

That’s the heart of it. Everything else is enclosure, ergonomics, and branding.

Nature’s Head does all of that in a clean, integrated package—and it does it well. But once you understand the underlying components, it’s hard not to look at that four-figure price tag and start doing the math.

I’m Not Above Building My Own

One thing about this build: I’m not afraid to get hands-on. I’m already designing and installing plumbing, electrical, propane, and HVAC systems.
So when I look at a composting toilet and realize it’s mostly smart carpentry plus a few key parts, the thought naturally pops up:

“I can build something just as functional for a fraction of the cost.”

And at this point, I really believe that.

The Nature’s Head is still a great product. It’s well-engineered, well-documented, and widely used. But $1,000+ (once you factor in tax and shipping) is a big chunk of budget for something I might be able to replicate for a couple hundred dollars and a weekend of focused work.

DIY Composting Toilet Kits Are Everywhere

Once you start looking, you realize there’s an entire ecosystem around DIY composting toilets:

  • Urine diverters you can buy as standalone components
  • 12V vent fans designed specifically for composting setups
  • Complete “guts only” kits that let you build your own enclosure

That last one is especially interesting: I can build a custom enclosure that fits my space, my height, my storage needs, and my aesthetic—without paying for a pre-molded shell that was designed for a generic use case.

In other words, I can design the toilet to fit the trailer, not force the trailer to fit the toilet.

Ventilation: The Real Key (And the Easy Part)

The more I read, the more one theme kept coming up: ventilation is what makes or breaks a composting toilet.

If you have:

  • A sealed solids chamber
  • A properly sized vent line
  • A small, reliable 12V fan pulling air out

…then odor control becomes very manageable. And those are all things I’m already dealing with in other parts of the build—fans, vents, penetrations, and airflow.

So from a systems perspective, a DIY composting toilet doesn’t feel like a stretch. It feels like one more small subsystem that plugs into the larger ventilation and electrical picture.

Where I’m At Right Now

On paper, the Nature’s Head is still the “official” toilet in my plans. It’s in the diagrams, it’s in the layouts, and it’s in the documentation.
But mentally, I’m in a different place now.

I’m keeping my options open. I’m not locked into a commercial unit just because I wrote it down early in the process.
As the build progresses and I get deeper into the details, the idea of a custom composting toilet—built around my space, my needs, and my budget—is becoming more realistic and more appealing.

The Takeaway for Today

Today wasn’t about buying anything or installing anything. It was about stepping back and asking a simple question:

“Does this expensive, off-the-shelf solution still make sense now that I understand how it works?”

Right now, my honest answer is: maybe not.

I’m not making a final call yet, but I’m also not blindly paying $1,000+ for something I can likely build myself for a fraction of that cost.
This build has always been about intentional choices, and the toilet is officially back on the “intentional choice” list.

For now, I’m going to keep researching DIY composting designs, sketching ideas, and watching how the rest of the systems come together.
When it’s time to commit, I want that decision to feel as solid as the rest of the trailer—not just “good enough,” but truly aligned with how I’m building this thing: thoughtfully, creatively, and on purpose.

Shower

DreamLine 36″ × 36″ Shower Base & QWALL‑5 Backwall Kit

Model: DL‑6194C‑01
Brand: DreamLine
Color: White
Material: Acrylic / ABS
Kit Includes: 36″ × 36″ Single‑Threshold Shower Base + QWALL‑5 Backwall Panels
Product Link:

View on Amazon

DreamLine 36x36 Shower Base and QWALL-5 Backwall Kit

Product Dimensions

Overall Kit Size (D × W × H): 36″ × 36″ × 76.75″
Shower Base: 36″ × 36″ (Center Drain)
Backwall Panels: Trim‑to‑fit design

Weights

Total Weight: 79.4 lbs

Key Features

  • SlipGrip textured floor surface for improved safety
  • High‑gloss, non‑porous acrylic for easy cleaning
  • Backwall panels made from Acrylic/ABS
  • Backwalls install over a solid surface (not directly to studs)
  • Base installs directly to studs; cUPC certified
  • Trim‑to‑size sidewall design for flexible installation
  • Lifetime Limited Warranty (base), 1‑year Limited Warranty (backwalls)

Tanks

Fresh & Grey Water Tanks for CTC Build

I plan to use these tanks as the core of my fresh and grey water system for the CTC build.
They were chosen for their durability, simple rectangular geometry, and reliable sizing that fits the layout of my front tank cabinet.
These specs will be used throughout my planning process for weight distribution, plumbing routing, and cabinet design.
The dimensions and capacities listed here reflect the exact tanks I will install in the trailer.

50 Gallon Fresh Water Tank — T5000BPK

Brand: classAcustoms
Model: T5000BPK
Capacity: 50 gallons
Material: Polyethylene
Product Link:

View on Amazon

Dimensions
  • Length: 14.25"
  • Width: 22.25"
  • Height: 38.25"

30 Gallon Grey Water Tank — T3000‑BPK (×2)

Brand: classAcustoms
Model: T3000‑BPK
Capacity: 30 gallons each
Material: Polyethylene
Product Link:

View on Amazon

Dimensions (Each)
  • Length: 12"
  • Width: 17.5"
  • Height: 34.5"