Water Is the Biggest Payload Lever on This Truck

Introduction

This dive starts where the Weight and Balance spine leaves off, because water turns out not to be a comfort topic at all.

⭐ THE FINDING: choosing to filter on site rather than carry water is worth more payload than any other decision left open on this build.

Table 1 — Introduction

Lever	Payload returned
Softshell instead of the hardshell tent	45 lb
5 gallons of water not carried	42 lb
10 gallons of water not carried	83 lb

Truck-only, this build has 221 lb of usable payload once fixed equipment and two adults are aboard. Ten gallons of water is 38 percent of it. Five gallons is 19 percent — very nearly the entire tent decision, available without giving anything up.

And the owner’s own observation is the reason it works: everywhere he goes there is a stream, a lake, or a river. The water is already there. The question is only whether it can be made safe, and how much equipment that takes.

1.1 What is actually owned today

Rotopax containers, and a few small LifeStraw filters for water bottles and hydration bladders.

🔴 The first thing to settle is a safety question, not a capability one: are those Rotopax the WATER version or the FUEL version?

Rotopax sells two separate product lines. The water containers are moulded in FDA food-grade plastic and come in 1, 1.75, 2 and 5 gallon sizes. The fuel containers are a different formulation and are not food-safe. ⚠ A fuel-spec container must never be used for drinking water, and a container that has held fuel cannot be reclaimed for it. The equipment list records only “Rotopax liquid containers,” which does not settle it.

Check the moulding on each one before any of this plan is acted on. If they are fuel-spec, they stay fuel-spec and water containers get bought separately.

1.2 What the small LifeStraws can and cannot do

They are excellent at what they are for, and they cannot do the job being asked of them here.

What they do: a personal straw or bottle filter is a hollow-fibre membrane, typically 0.2 micron. It removes bacteria and protozoa — Giardia and Cryptosporidium, the two that actually make people ill in North American backcountry — to very high log reductions, along with microplastics and sediment.

🔴 What they cannot do is fill a container. A personal filter cleans water at the moment of drinking. The water in the bottle is still raw; the straw treats each mouthful on its way past. There is no way to use one to produce a stock of clean water, and that is precisely the operation the Rotopax plan requires.

⭐ So the gap is real and specific: the owner has point-of-use treatment and needs point-of-supply treatment. Those are different products, and no amount of patience with a straw bridges it.

Two further limits matter later in this dive: a hollow-fibre filter does not remove viruses, and it does not remove anything dissolved — chemicals, heavy metals, or algal toxins. The next volume deals with both.

1.3 The arithmetic of filling on site

Water weighs 8.34 lb per gallon, which is the whole reason this matters.

Table 2 — The arithmetic of filling on site

Carried	Weight	Share of the 221 lb truck-only budget
2 gal	16.7 lb	7.5%
5 gal	41.7 lb	19%
8 gal	66.7 lb	30%
10 gal	83.4 lb	38%

A 2-gallon Rotopax is about 4 lb empty and about 21 lb full. Sixteen of those twenty-one pounds are water that is available for free at the destination.

⚠ This is not an argument for arriving with nothing. Two things argue against a completely dry departure:

A reserve is a safety item, not a convenience. A source can be dry, fouled, in an algal bloom, or on the wrong side of a washout. ⭐ The sensible pattern is to carry a small guaranteed reserve and generate the rest on site — enough to get home on, not enough to camp on.

And filtering takes time and filter life. A gravity system fills a 5-gallon container in perhaps fifteen minutes of unattended dripping, which is nothing at camp and irritating at a roadside stop.

⚠ And note that this dive ends up recommending that all water be filtered, showers included — see vol 2. That raises the volume filtered but not the volume carried, so it does not change the arithmetic here.

✅ ADOPTED 2026-08-30 — this is now the plan. ⭐ The pattern that fits this build: depart with roughly 2 gallons of known-good water as reserve, and carry the rest of the containers empty. That is about 17 lb aboard instead of 83, and it hands 66 lb back — half again what the tent decision is worth.

1.4 What this changes upstream

✅ DONE — the load plan now carries 2 gallons at 21 lb. ✅ The reserve is now ONE gallon, and the filter is specified: a portable hybrid + RO unit at 13 lb. Filter and reserve together are 25 lb against 66 lb for eight gallons — a 41 lb saving. 🔴 But two consequences followed that this volume did not anticipate. First, the water was the trailer’s tongue-weight trim control, and at 21 lb its authority across the whole rail falls to about 10 lb — the fridge and the front-trunk bedding take over. Second, and larger: 🔴 making water on site makes the filtration gear load-bearing. It is now budgeted at 13 lb and it is the water supply rather than a convenience. ⚠ Three operational consequences that follow from RO specifically: it rejects three to four gallons for every one it makes, so it needs a volume source rather than a seep; the membrane must not freeze and must not dry out, which is a storage problem in a Michigan truck bed; and it is slow — an evening chore, not a fill-up. → Weight and Balance vol 3.

⚠ It does not change the fixed-equipment problem. Eight hundred and seventy-nine pounds of rack, tent, drawers and people is still 80 percent of the payload, and no amount of clever water management touches it. Water is the largest lever among the things still open, not a solution to the things already decided.

References

• Water density: 8.34 lb per US gallon.
• RotopaX — separate water and fuel product lines; water containers in FDA food-grade plastic, 1 / 1.75 / 2 / 5 gallon.
• LifeStraw personal and bottle filters — 0.2 micron hollow-fibre; bacteria and protozoa removal, no virus removal, no dissolved-contaminant removal.
• Weight and Balance, this project — the 221 lb truck-only budget these figures are measured against.