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Plumbing

In progress Spend: -
Fill underfloor + gravity Vent 3/4 in, screened Fresh tank 41 gal poly, no baffles Strainer 255-313 Pump Shurflo 4008 Accumulator 182-200 COLD TRUNK Kitchen sink hot + cold Indoor shower hot + cold Outdoor shower undermount box RO unit iSpring 500 · 2:1 Engine coolant primary heat Isotemp heater 4.2 gal · mixer 120F HOT TRUNK HepvO traps waterless Diverter 3-way · fail-safe ground To ground default Grey tank 15-20 gal

Trunk and branch, not home-run manifolds. One 1/2 in PEX trunk each for hot and cold runs the length of the box, and each fixture tees off it. The earlier home-run manifold plan was dropped: it doubled the tubing, needed a manifold body with a dozen ports in a bay that turned out to be 25.5 x 17.5 x 20 in, and bought nothing a branch valve does not.

Every subsystem isolates. A main shutoff sits at the tank outlet, the pump group has a valve each side, the heater has three (cold in, hot out, bypass), and the galley, both showers and the RO each have their own. Any one can be worked on with the rest of the truck live.

The full build, drawn phase by phase with every part, its supplier and its part number, is in the water system journal entry. That entry is the source of truth; this page is the summary.

1Fresh water tank

TankClass A Customs T-4100, purchased Jun 2026
MaterialPolyethylene, NSF approved
Capacity41 gallons
Size39" × 16" × 16.63", two 1.5" + two 1/2" FNPT ports

An earlier plan for a custom 304 stainless tank from Cmax-Inox was dropped; the off-the-shelf poly tank was purchased instead. No baffles, which matters for level sensing while driving. Lives in the lounge bench with the pump and accumulator, in a pocket measured 2026-07-27 at 25.5 x 17.5 x 20 in.

2Pump & pressure

PumpShurflo 4008-101-A65 (12V, 3.0 GPM, 55 psi)
StrainerShurflo 255-313, twist-on bowl, 1/2" NPSM, inlet side
AccumulatorShurflo 182-200, 24 oz, 30 psi pre-charge

3Water heater

Isotemp Slim Square, 4.2 gal. It lies on its side in the water bay, gable aft, on union fittings so it lifts out: the pocket is 20 in high and the heater is 23.25 in over its brackets, so standing it up was never possible. Two co-primary heat sources rather than a primary and a backup:

Idling the engine just for heat is treated as a fuel-inefficient last resort. Coolant lines route along the chassis frame rails, under the composite floor.

A thermostatic mixing valve on the hot outlet is not optional here. Engine coolant runs near 90 C, so unlike an electric-only heater this tank can deliver water that scalds in about a second. The valve blends cold back in and holds delivery near 49 C. It also makes 4.2 gal go further, because you store hot and blend down.

4Fixtures

Three endpoints, each branching off the hot and cold trunks behind its own pair of isolation valves:

Build log

No photos yet. Newest will show first as they come in.