5th Gen 4Runner Water System With Trail’d Tanks – Full DIY and How-To Guide

The Trail’d Universal 6 Gallon “Spare” Tank – Complete Installation Guide on 5th Gen 4Runner

If you take your rig overlanding for a weekend or more, a good water system can make or break your camping experience. Convenience is key when you would like to have access to drinking water, running water to wash dishes, or a nice sprayer to hose off muddy mountain bikes or sandy toes.

This DIY water setup will cover a comprehensive plumbing system and various outlets that serve every need – all within your 4Runner. We’ll go through all the materials used in this build, as well as lessons learned along the way. In particular, we’ll focus on the heart of the water system – the Trail’d “Spare” tanks that houses 12 gallons of potable water and feeds the rest of the system. If you’re looking for the ultimate solution in glamping hydration, keep reading.


  • Trail’d Universal 6 Gallon “Spare” Tank: Check Price
  • SEAFLO 12v 3.0 GPM 45 PSI Water Pressure Pump: Check Price
  • SEAFLO Pre-Pressurized Accumulator Tank: Check Price
  • Gravity Fresh Water Fill Hatch Inlet: Check Price
  • Flex-Fill 1-3/8″ x 10′ Hose: Check Price
  • Dura Faucet Quick Connect Sprayer, Hose, and Utility Spray Dock Kit: Check Price
  • Coarse Thread Cap: Check Price
  • Aluminum Commercial 8″ x 8″ Square Cake Pan: Check Price
  • Foldable RV Faucet: Check Price
  • Moen 22174 Sink Basket Strainer with Drain Assembly: Check Price
  • Camco Flexible Camper Drain: Check Price
  • Polypropylene 90 Degree Elbow, 1/2″ NPT Male x 1/2″ Barbed: Check Price
  • 1/2″ Hose Barb to 1/2″ Male NPT 304 Stainless Steel Hose Fitting: Check Price
  • 1/2″ Hose Barb to 1/2″ Female NPT 304 Stainless Steel Hose Fitting: Check Price
  • 5/8″ Brass and Steel Quick Hose Disconnect: Check Price
  • 90 Degree Barstock Street Elbow, 3/4″ Male x 3/4″ Female: Check Price
  • 90 Degree Forged Street Elbow, 1/2″ Male x 1/2″ Female: Check Price
  • Brass Pipe Female 4 Way Y Cross Fitting 1/2″ NPT: Check Price
  • 1/2″ ID x 3/4″ OD – 10 Ft High-Pressure Braided Clear PVC Vinyl Tubing: Check Price
  • Inline Tee Adapter, 1-1/4 Barbed Male x NPT Male: Check Price
  • Elbow, 1-1/4″ Hose ID, 1-1/4 NPT Male: Check Price


  • 1/2″-14 NPT Pipe Tap
  • 3/4″-14 NPT Pipe Tap
  • 1-1/4″-11 NPT Pipe Tap
  • Teflon tape/non hardening pipe dope
  • Assorted hose clamps
  • Wrenches

Trail’d “Spare” Tank: Initial Thoughts

Trail'd "Spare" Tank

Let’s talk about water storage. The most simple solution is to carry around heavy water jugs, ranging in volumes from 3 to 6 gallons. Not the most convenient task when you have to haul out a 40lb tank full of water every time you need a drink. I carried two 3-gallon jugs for years before I upgraded to a solution I finally love – the Trail’d Universal 6 gallon “Spare” Tank.

What makes the Trail’d tank a great solution is the versatility it provides – it is stored in an ultra-convenient spot (replaces your spare tire under the vehicle so it doesn’t take up valuable interior space) and it can function as either a portable water jug or remain mounted as a water tank that feeds a pump. It includes a coarse thread fitting with a spout, but you are able to modify it as needed for your own application (we’ll go into that later).

Another great feature is the ability to stack multiple tanks – you can fit up to three tanks under your rig for a total of 18 gallons of water storage! However, they recommend a maximum of two tanks (12 gallons total) if you plan on going offroading. I opted to add several of my own fittings and stack two tanks to feed an integrated water system in my 4Runner.

Water System Design

Trail'd "Spare" Water Tank System Design

The first water system I designed used a single Trail’d tank. On multi-day trips, the convenience of running water had me going through all 6 gallons too quickly – washing dishes in a sink instead of sparingly rinsing off the dishes with one of my water jugs. Since I wasn’t willing to be more frugal with water usage, I threw in a second tank – because why not

Let’s talk about how I set up twin tanks that feed a single pump which in turn diverts the water into three separate outlets. To cover all water applications, I incorporated a sink with a faucet in the pullout kitchen, a sprayer quick connect in the rear bumper and a standalone spigot in one of the rear MOLLE panels for filling up water bottles or dog bowls on the go. There’s also a gravity fill inlet that is conveniently integrated into the bumper to fill both tanks.

Two Tank System Integration

Two 6-gallon Tank System Integration

Plumbing together two tanks to feed a single system was a challenge. Not only do you have to make sure both tanks gravity feed to the same pump inlet, but you also have to figure out a single gravity fill solution for both tanks, and ventilation to ensure both tanks are able to fully empty themselves.

I wanted high throughput at ambient pressure in the tanks, so I opted for 1 1/4” fittings for both the inlet and outlet. The gravity fill port already used 1 1/4″ tubing, so it was convenient to align the rest of the fittings to the same size.

Connecting the Two Water Tanks

hose connecting two 6-gallon water tanks

The tanks sit at a slight angle when mounted under the truck (similar to your spare tire), so the water is biased towards one side. I wanted to take advantage of that, so in my single tank design, I added a 1/2″ NPT x 1/2″ barb threaded into the base of the tank to connect to the pump.

It worked well, so I carried it over into the twin tank design – only on the lower tank though. In order to facilitate flow between the top and bottom tanks, I added two 90-degree 1 1/4″ NPT to 1 1/4″ barb fittings connected by a hose. This allows water from the top tank to fill the lower tank as water is drawn by the pump. Don’t forget the hose clamps!

Water Tank Vent System

6-gallon water tank vent system

To fill both tanks together, I incorporated a similar design as the outlet. Instead of two 90 degree elbows, however, I combined one tee and one elbow. The fittings are positioned along the perimeter such that they align with the gravity fill port installed in the bumper.

A critical feature to take note of is the venting for each tank. When you fill both tanks with water or alternatively pull water out, air either needs to escape or backfill the tanks. Not only that, but each tank needs its own venting to ensure proper flow.

If the tanks aren’t properly vented, the water will stagnate at some point in the system – similar to how water will hold itself in a drinking straw if you cover one end with your finger. You can see the two vent fittings on the left face of each tank; they’ll both be connected to a 1/2″ hose that routes up into the rear quarter panel.

SEAFLO Water Pump

Seaflo 3.0gpm Water Pump

Now that we have our water storage sorted, let’s take a look at what drives the fluid flow. This SEAFLO 3.0gpm pump is plenty powerful for our application and has some convenient features like self-priming and auto-shutoff. This means that the pump can pull water up from the tanks while dry, and will turn off when the pump outlet reads at a certain pressure threshold.

In conjunction with the pump, I’ve included an accumulator tank in series to smooth the flow for a more consistent output. The system also includes a pre-filter to make sure no contaminants from the tanks get into the pump. In the image above, you can see the series of 1/2″ NPT fittings that I’ve used to connect everything together – right side coming in from the Trail’d tank and left side going out to the various outlets.

Water Pump Mounting

4Runner Water Pump Mounting

Since the water system is a permanent addition to the 4Runner, we need to find a convenient location for the mounting. I ended up cutting out one of the cubbies in the trunk to expose the inside of the rear quarter panel – perfectly sized for the pump and accumulator tank. Both are mounted to the plastic bezel with a custom fabricated bracket, and rubber isolators damp vibrations from the pump. I used 1/2″ tubing with braiding to connect the pump to the Trail’d tanks.

Water Distribution

water pump brass distributor

Now that we have the main system complete, it’s time to split off the water output from the pump to our various outlets. This brass distributor with 1/2″ NPT x 1/2″ barbs does the job. One inlet, three outlets – one for the sink faucet, one for the MOLLE panel spigot, and one for the bumper sprayer. Let’s dive into each.

Sink with Folding RV Faucet

Sink with Folding RV Faucet

The sink is my favorite outlet in the system – running water is a premium commodity and it makes washing veggies, rinsing dishes, and cleaning your hands a breeze. The sink is actually an 8”x8” brownie tin combined with a drain and folding RV faucet.

Water is connected to the faucet via quick-connect fitting – plumbed from the distributor. Since our pump has auto-shutoff, we can use the faucet valve as we would in a normal sink – the pump will turn on when the valve is opened and water starts flowing out of the system, and turn off when the valve is shut.

Quarter-turn Shut-off Valve

Quarter-turn Shut-off Valve Installation

With this iteration of the water system, the supply line from the distributor needs to be pulled out of the rear quarter panel cubby and plugged into the sink. The hose from the distributor has a quarter-turn shut-off valve in line before the quick connect fitting to the faucet. The drop-in drain threads into a low-profile 3D-printed coupling exiting to the drain hose. In the next iteration, the plan is to have an always-plumbed water hose coil that extends and retracts with the pullout kitchen.

Water Spigot

water spigot within rear MOLLE panel

The spigot in the rear MOLLE panel is convenient for getting drinking water while the kitchen is closed. In fact, it can be accessed through the rear hatch window for quick fill-ups. The spigot plumbing passes through the interior panel and connects to the distributor via a 1/2″ tube. Since it’s a tight fit around the 3rd-row seatbelt within the D pillar, a 1/2″ NPT elbow is necessary for proper water flow.

Bumper Sprayer

hose with sprayer nozzle mounted on 4Runner bumper

The final outlet is the bumper sprayer. It’s tight plumbing within the bumper, but some creative use of fittings will let you twist through the tight angles and connect back to the distributor. You’ll definitely need at least one 1/2″ NPT male-to-female elbow.

Highly convenient for hosing off muddy mountain bikes or washing sandy toes. You can even set up an external portable sink using this sprayer if you don’t have an integrated kitchen as I do.

The SEAFLO pump provides plenty of water pressure so you can easily use all of the different modes the sprayer includes. As a testament to the power and convenience of this setup, we had to use the jet setting on the sprayer to hose out a radiator caked with mud when my buddy’s truck began overheating trailside.

Final Thoughts

Sink with Folding RV Faucet and Bumper Sprayer

Let’s talk about how this setup has held up over the past 5 trips. It’s seen snowy winter trails and hot desert dunes. Been through mud pits and across rock gardens. Overall, the system is extremely robust and has held up just fine.

The Trail’d tanks are exposed in cold weather so the water could freeze overnight – essentially killing your water supply unless you keep an emergency water jug inside the cabin where it’s warmer. Of course, the proximity to the exhaust will warm everything right up once you hit the trails again.

I’ve also found that the weight of 12 gallons of water causes the tanks to sag a bit around the small spare tire suspension bracket. To mitigate this, I’ve added a plywood circle that interfaces with both the bracket and the tanks, offering support and some protection against rough terrain.

Aside from these minor issues, I have nothing but praise for the Trail’d tanks. They are convenient, robust, and allow you to be endlessly creative with how to integrate them into your particular setup. On top of that, the pump and plumbing have proven to be more than sufficient for any overlander that’s looking for high-pressure water at the flip of a switch. Let me know how you end up using your tanks!

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11 months ago

Like another person mentioned on here, that I guess figured it out (I still cant LOL) where is the outlet tube going to the pump? I clearly see the pipes connecting the two tanks (that also act as the fill location) and the Vents but where is the outlet that goes to the pump, is that shown on the opposite side of the tanks in the very first photo?

Also, since there two tanks are interconnected via the fill pipes is there a need for a vent on Both? Couldnt one just vent the top tank?

1 year ago

Hi Sanju,
Great idea and implementation!!
your 4Runner looks awesome!!
I have a question; how were you able to bring the hose from the bottom (tire well) to inside the cabin where you have the pumps installed?
I have the OEM bumper currently.
Any inputs greatly appreciated!


2 years ago

Sanju – I am confused – I see you have the Vent, the Fill, and 2 Tank Connector. But where are you connecting the pump?

2 years ago
Reply to  Bobby

Yea I am still confused by that as well. I don’t see it hooked up or where it could be hooked up.

2 years ago
Reply to  Chris

I figured it out. This image is where he connects the two tanks comment image), but he mentions the following

The tanks sit at a slight angle when mounted under the truck (similar to your spare tire), so the water is biased towards one side. I wanted to take advantage of that, so in my single tank design, I added a 1/2″ NPT x 1/2″ barb threaded into the base of the tank to connect to the pump.

It worked well, so I carried it over into the twin tank design – only on the lower tank though. In order to facilitate flow between the top and bottom tanks, I added two 90-degree 1 1/4″ NPT to 1 1/4″ barb fittings connected by a hose. This allows water from the top tank to fill the lower tank as water is drawn by the pump. Don’t forget the hose clamps!

So the picture shows what is after the bolded text, but there is a barb on the bottom tank to connect to the pump.

Colby D Long
Colby D Long
2 years ago

Hey Sanju, I’m looking to replicate this build and have a couple of overview questions: can you describe the gravity fill install? and does that SeaFlo pump have an automatic kill switch if pump is ran without water?

2 years ago

Great idea! really good!

2 years ago

Love the addition of the tanks, looked at those too but didn’t want the hassle of supporting and accessing them. I went with a 14 gal tank made by Plastic-mart who customizes RV tanks; fits right up in where the spare was. Plumbed in is a Shurflo pump with accumulator for constant flow and pressure. I installed two quick connects inside each bottom corner of the rear hatch into the bumper, one for fill and the other to connect my hose along with shut-off valves. Surprising how much room is between the hatch and the bumper when shut and you don’t see the hose attachments when the rear hatch is closed. Added a custom skid plate that mounts to existing threaded holes in the frame rails to support the tank and add protection. Details on http://www.4runners.com under 5th gen builds.

2 years ago
Reply to  Sanju Bose

Did you find the install?

2 years ago
Reply to  Mark

Thanks for the link. Great work!

2 years ago
Reply to  Mark

Me either

2 years ago
Reply to  Mark

That sounds cool too, but had trouble finding it there. Are direct links allowed?

2 years ago
Reply to  James

I couldn’t find it either

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