[ Living Off-Grid ]

Off-grid living is really three budgets that feed each other: power
(watt-hours), water (gallons), and fuel (propane, mostly). Every appliance is
a withdrawal from one or more of them, and the places they cross over are where
it gets interesting. The 12V pump that pressurises your shower spends
watt-hours to move gallons, and the heater on the end of that line burns
propane to make them warm.

Get those three budgets right and off-grid is comfortable. Get them wrong and
you are cold, in the dark, or hauling water by hand. This page is the map. It
starts with power, because nothing else runs without it, then goes deep on the
one system people always underestimate: hot water and a real shower.

It is a living document. Right now it covers power, the hot-water shower loop,
and a biosand water filter. Cooking, refrigeration, heat, and connectivity get
their own sections here as those builds get documented.

Power comes first, because every other system leans on it, and on this site it
already has its own guides. How the pieces fit:

  — Generation. Solar is the default: silent, no moving parts, and it tops
    up while you are out. Sizing an array, wiring it in series or parallel, and
    choosing a PWM or MPPT controller is the Solar Power Basics guide, start to
    finish.
  — Storage. A battery bank is where that solar actually lives, and lithium
    (LiFePO4) is the modern answer: light, deep-cycling, and flat under load.
    Size a pack with the Battery Pack Calculator, then build and protect it with
    the Daly BMS or 5S BMS guides.
  — Distribution. Most off-grid loads are 12V DC straight off the battery:
    lights, fans, and the water pump below. Fuse every branch at the battery and
    size the wire to the fuse, not to the load. The tool-battery guide walks the
    same fusing logic on a smaller pack.

The rule that ties it together is the energy budget: add up the watt-hours
everything draws in a day, then build generation and storage to cover it with
margin for a cloudy week. The water pump is a small line on that budget, but it
is the line between you and a hot shower, so it earns its watt-hours.

This is the system people skip and then regret. A hot shower off-grid is not a
luxury build; it is four cheap parts in a line:

  reservoir  →  12V pump  →  propane tankless heater  →  shower head

Cold water sits in a reservoir (a tank, a jug, a bladder, even a clean bucket).
A 12V pump pulls from it and pushes pressurised water through a propane
tankless heater, which fires only while water is moving and heats it on the way
through. Out the far end is an ordinary shower head. No tank of hot water
sitting around losing heat, no waiting, and the whole thing runs off a battery
and a propane cylinder.

Why the pump is not optional. A tankless heater needs a minimum flow and a
minimum pressure before it will fire its burner, typically around 0.4–0.6 GPM
and a few PSI. Gravity from a reservoir a couple of feet up only dribbles and
never reaches that threshold, so the burner never lights. The 12V pump is what
makes the heater behave as if it is plumbed into a house.

The pump. A 12V diaphragm pump, the RV or marine kind (think Shurflo or a
clone), is the right tool. Two numbers matter:

  — Flow (GPM). Match or beat the heater's activation flow, with margin. A
    pump rated 1.0–1.5 GPM comfortably fires a small tankless and still gives a
    real shower stream. Too little flow and the burner stutters or cuts out.
  — Pressure and the switch. These pumps carry a built-in pressure switch:
    they run until the line reaches cut-off (30–45 PSI), then stop. Open the
    shower valve, pressure drops, the pump runs; close it, the pump stops on its
    own. That is your on/off, with no relay needed.

Wire the pump like any other 12V branch off the battery: a fuse at the battery
end sized just above the pump's running current (a 4–6A pump wants a ~7.5A
fuse), wire gauge sized to that fuse, and a switch on the positive leg if you
want to kill it fully. This is the same fusing logic as every other 12V load in
the tool-battery and DIY pack guides.

The heater. A propane tankless (on-demand) heater is rated by temperature
rise at a given flow, not by one "hot" number. It lifts the incoming water by so
many degrees; how hot the output is depends on how cold the input is and how
fast it flows:

  — Cold groundwater in winter gives less rise at the same flow, so you turn
    the flow down for the same output temperature, or turn the gas up. Reservoir
    water that has sat in the sun all day needs almost no help.
  — Water on before gas, off after. Flow proves first, then the burner
    lights. Never light a tankless dry.
  — Hard water scales the heat exchanger. If your source is hard, flush the
    heater with vinegar now and then.

The reservoir. Size it per shower, not per day. A genuinely quick off-grid
shower is 2–4 gallons; a generous one is 5–7. A 7-gallon jug is one good shower
or two quick ones. Keep the inlet screened so grit never reaches the pump or the
heater, and keep the reservoir where a self-priming pump can actually draw from
it.

The build these photos come from. This setup lives in an enclosed toy-hauler
trailer, sharing the space with a dirt bike:

  heater      Foruee propane tankless, GAS + WATER knobs, digital temp
  pump        12V diaphragm pump, on-demand pressure switch
  power       marine battery box, 12.8V on the meter, 6-slot fuse block
  switching   a WATER PRESSURE panel toggle cuts the pump; its own pressure
              switch handles on-demand shut-off at the shower valve
  shower      braided hose and head off the heater's hot outlet

The heater's own warning label spells out the two rules that matter most: check
every gas joint with soapy water, and drain the unit before it can freeze. The
propane is not connected in these photos; when it runs, it runs with the ramp
door fully open, treated as open air. Read the safety section
before you copy any of it.

The shower loop above assumes you already have water. A biosand filter is
how you make questionable water usable: a barrel of sand and gravel with a
living biolayer on top that eats the pathogens as water trickles through.
No power, no cartridges to buy, no moving parts. It is the household version of
the slow sand filters that treat whole towns, shrunk to a drum you can build in
an afternoon.

What it does, and what it does not. Be honest about this before you trust it
with your gut:

  — Removes most bacteria, protozoa (Giardia, Cryptosporidium), worms, and
    the turbidity that makes water cloudy. A ripe filter clears most viruses
    too, though not every last one.
  — Does not remove salt, dissolved chemicals, heavy metals, or fuel, and it
    leaves no disinfectant behind. It is a filter, not a desalinator and not a
    chemistry set.

Treat it as the middle of a chain, not the end of one:

  murky source  ─►  biosand filter  ─►  disinfect  ─►  safe to drink

The filter takes out the germs and the cloudiness; the disinfection step (a few
drops of bleach, a rolling boil, or a UV pen) mops up the viruses it misses. For
washing, laundry, and flushing, water straight off the spout is fine. For
anything you swallow, finish it, and do not skip that on the strength of
clear-looking water.

How it goes together. Top to bottom, what lives in the barrel:

  standing water    ~5 cm on top; if it ever drains dry, the biolayer
                    starves and dies
  biolayer          the living skin at the sand surface; forms over 1-3
                    weeks and does the actual work
  fine sand         40-55 cm, the filtration bed; wash it until the
                    rinse water runs clear
  separating gravel ~5 cm; stops sand migrating down into the drainage
  drainage gravel   ~5 cm of coarse gravel; feeds the outlet
  outlet            a tube from the bottom, up the outside, to a spout
                    set ~5 cm above the finished sand

The outlet-spout height is the whole trick. Because the spout sits about 5 cm
above the top of the sand, water only ever drains down to that line and then
stops, leaving the biolayer permanently wet between uses. Set it too low and you
drain the biolayer; too high and the top floods.

Building it:

  1. Container. A food-grade barrel or a concrete cast, opaque so light does
     not grow algae inside.
  2. Plumb the outlet from the bottom drainage layer, up the outside, ending
     in a spout ~5 cm above where the sand will finish.
  3. Wash the media obsessively. Rinse sand and gravel until the water runs
     clear. Unwashed fines are the number-one reason a filter runs muddy.
  4. Layer it in: drainage gravel, separating gravel, then the fine sand,
     poured in under water so no air pockets get trapped.
  5. Add a diffuser, a perforated plate or basin above the water, so pouring
     does not gouge the biolayer.
  6. Ripen it. Run water through daily for 1-3 weeks so the biolayer
     establishes before you rely on it.

Living with it. Pour a batch in, collect the clear water, then leave it. The
pause between batches, an hour to a day or two, is when the biolayer feeds
and stays healthy, so intermittent household use is exactly what it wants. When
the flow slows, swirl the standing water and scoop off the dirty top without
digging into the sand, then let it re-ripen for a few days. Keep it above
freezing, like the rest of the water system.

The bottle version is a demo, not the real thing. The classic cut-bottle
filter, pebbles over gravel over charcoal over coarse then fine sand, with a
cotton plug at the neck, is a great way to see the layering and to knock the mud
and some taste out of water in a pinch. But it is not a biosand filter: it has
no standing water and no established biolayer, so it does not do the biological
pathogen removal that makes a real filter worth trusting. Use it to understand
the layers or as a rough sediment pre-filter, then still disinfect anything you
plan to drink.

This setup has two ways to hurt you that the solar and battery guides do not:
combustion and scalding. The electrical side you already know from the pack
guides. Take the combustion part seriously, because it is the one that kills
people quietly.

Carbon monoxide is the real danger. A propane tankless heater burns a flame
and produces carbon monoxide. CO is colourless, odourless, and it can kill
before you know it is in the room.

  — Never run a propane tankless in an enclosed space. Not a closed
    bathroom, not a tent, not a van with the doors shut, not a garage. These
    units are outdoor-rated for a reason, and "cracked a window" is not
    ventilation.
  — Mount the heater outside the shower space, in open air, and run the hose
    to the shower head. You wash where the water is, not where the flame is.
  — Put a CO detector in any sleeping or living space that shares air with
    where the heater runs. A battery CO alarm costs a few dollars and it is the
    cheapest life insurance you will ever buy.

Propane handling. Treat the fuel with the same respect.

  — Leak-check every connection with soapy water when you set up. Bubbles
    mean a leak, and a leak means you stop and fix it before you light anything.
  — Use the regulator that came with the heater. Do not plumb a heater
    straight onto a high-pressure tank.
  — Store cylinders upright and outside, away from spark and heat. Propane is
    heavier than air and pools in low spots, so never keep a cylinder in a
    below-deck or sunken space.

Scalding. A tankless with the gas up and the flow down can put out water hot
enough to burn. Set the temperature with your hand in the stream, not your body,
and remember that turning the flow down makes the output hotter, the opposite
of a house tap.

Water and winter. Two smaller ones:

  — Freeze protection. Water left in the pump and heater will freeze and crack
    them. Drain the loop, or blow it out, before a hard freeze.
  — Potability. This loop is for washing. If the reservoir is not potable
    water, keep it clearly separate from anything you drink and never
    cross-connect the two.

Do I really need a pump, or can gravity feed the heater?
You need a pump. A tankless heater has to see a minimum flow and pressure,
around 0.4–0.6 GPM and a few PSI, before the burner fires. Gravity from a
reservoir a couple of feet up only dribbles and never reaches that threshold.
A 12V diaphragm pump pressurises the line so the heater behaves as if it is
plumbed into a house.

What size 12V pump do I need?
A 12V diaphragm pump (RV or marine, a Shurflo or a clone) rated about 1.0–1.5
GPM fires a small tankless and gives a real shower stream. Its built-in pressure
switch runs the pump until you close the valve, then stops it, so no relay is
needed. Fuse it at the battery just above its running current.

Is it safe to use a propane tankless in a bathroom or tent?
No. It burns a flame and produces carbon monoxide, which is colourless,
odourless and deadly. These units are outdoor-rated and must run in open air,
never a closed bathroom, tent, van or garage. Mount the heater outside, run the
hose in, and keep a CO detector in any space that shares air with it.

How much water does an off-grid shower use?
A quick shower is 2–4 gallons; a generous one is 5–7. A 7-gallon reservoir is
one good shower or two quick ones. Size the reservoir per shower, not per day,
and screen the pump inlet so grit never reaches the pump or heater.

How do I power the water pump off-grid?
It is a normal 12V DC branch straight off the battery bank, like your lights and
fans. Fuse it at the battery just above the pump's running current (a 4–6A pump
wants roughly a 7.5A fuse), size the wire to that fuse, and add a switch on the
positive leg. Same fusing logic as the battery pack and tool-battery guides.

Is biosand-filtered water safe to drink?
Not on its own. It removes most bacteria, protozoa, worms, and turbidity, and a
ripe filter clears most viruses, but it leaves no residual disinfectant and does
not remove salt or dissolved chemicals. For drinking, finish it with a step of
disinfection: a few drops of bleach, a rolling boil, or a UV pen. For washing
and laundry, straight off the spout is fine.

How long before a biosand filter works?
One to three weeks. The biolayer, the living skin of microorganisms at the top
of the sand that does most of the pathogen removal, has to establish first. Run
water through daily during that time, and keep about 5 cm of standing water on
top always, so the biolayer never dries out and dies.