Water

How not to run out of the one thing you can't do without.

You can go three weeks without food, and about three days without water. So it comes first — and it rewards clear thinking more than money or luck.

Of everything a household leans on, water is the one you can least do without. You can last about three weeks without food. Without water, about three days.

To merely stay alive, a person needs only two or three litres to drink. To stay well — to cook, wash, and not fall ill — the recognised emergency minimum is around 15 litres a day. But nobody wants to live at the emergency minimum for a year. Comfortable, ordinary living runs closer to 100 litres per person, per day — which for a family of four is some 400 litres a day, and across a year nearly 150,000 litres. That is precisely why water can't simply be stockpiled in a drum in the corner. It has to be planned.

01
The shape of the problem

It isn't one problem. It's four.

The first clear thought is that you are not solving one thing called "water." You're solving a handful of smaller ones that travel together — and telling them apart is half the battle. Hold these apart in your mind and the whole subject stops being a fog and becomes a set of decisions.

Drinking & cookingsmall · must be clean

The water that must be pure — and, surprisingly, the smallest quantity of the four. It's the only water worth treating to drinking standard.

Washinglarge · forgiving

You, your clothes, your dishes. A big volume, but it tolerates rougher water — it never needed to be pure.

Flushingthirsty · needs no cleanliness

Thirstier than anyone expects, and it doesn't need clean water at all — only wet water. The scandal hiding in every bathroom.

The reservethe cushion that matters

The one that really counts: the buffer that carries you across the dry stretch when nothing is coming in.

The animalsthey drink too

Any livestock or pets drink from this system as well — a cow wants forty litres a day, a dog a couple. Small in number, easy to forget, and thirsty when forgotten.

Drinkingsmall · must be pure
Washinglarge · forgiving
Flushingthirsty · needs no clean
The reservethe cushion

Rough share of a day’s water — the pure part is the smallest.

02
The principle everything rests on

Plan for the worst day, not the average.

You are not planning to have water. You're planning to have water on the worst day.

The dry week in the hot season, when the tank is low, the power's out, and the tanker you'd normally call isn't answering — because the whole neighbourhood had the same clever idea at once. Plan for the average and the worst day will find you out. Plan for the worst day and the good days take care of themselves. Almost everything that follows is just this one idea, applied patiently.

You are not planning to have water. You are planning to have water on the worst day.

03
Before you plan, learn to see it

Spend a day watching where it goes.

Before you can plan water, you have to notice it — and most of us genuinely can't, because it's so cheap and constant it has slipped beneath our attention. So watch it for a day. Not measuring, just watching: the glass and the cooking pot, the shower, the toilet flushing away clean water like it's nothing, the laundry, the floors, the plants.

Two things swim into focus, and they shape the whole plan. First, a great deal of your water goes to jobs that never needed it clean. Second, the part that truly must be pure — drinking and cooking — is surprisingly small. Of the hundred-odd litres a person gets through in a day, only a handful must be drinking-clean. That gap is your entire strategy in a single glance: treat the little that must be clean, and use rougher water for all the rest. Skip this and you end up purifying your whole supply to drinking standard — washing the floor with something close to bottled water — and wondering why the costs and the power bills climb.

04The move that halves the workMatch each grade of water to a source.Read more

Here is the whole strategy in one sentence: not all water has to be the same, so not all of it has to come from the same place. Once you've split your need into grades — the pure, the tolerant, the rough — you plan each one separately, matching its demand to the cheapest supply that's good enough for it.

Potable — small demand, made clean

Drinking and cooking is the smallest need, but the only one that must be pure. You don't hunt for a clean source; you take a little from your store and treat it on the way to the glass. Demand is low, so the treatment burden is low.

Washing — large demand, tolerant supply

Bathing, laundry, dishes: a big volume that never needed to be pure. Met from the general store and harvested rain, filtered enough to be pleasant — not purified to drinking standard. Matching this large demand to a rough supply is where most of the saving lives.

The rough end — flushing and the garden

Flushing and watering ask only for wet water, fed from the lowest grade of all — reclaimed greywater and rain — so your precious clean water is never wasted on them.

So the real planning is two columns, grade by grade: how much of each you need, against how much of each you can supply — rain caught, water stored, greywater reclaimed, tanker bought. Where a grade's demand outruns its supply, you find more of that grade or downgrade the need. Balance the columns and the year holds.

05The decisions that actually matterA few choices are the whole song.Read more

How much is "enough"?

There isn't one number — there are two. A comfortable amount, what you'd like to use; and a survival floor, the line below which health genuinely suffers. In a good month you live in comfort; as the reserve drops you ease down toward the floor but never below it, buying emergency water only to defend the floor, never to prop up comfort. As a rough anchor, humanitarian agencies put the bare emergency minimum near 15 litres per person a day, with 50–100 for something like normal dignity — set your floor at a real health minimum for your climate and treat it as sacred. A floor you defend and a comfort you flex — hold those two, and water becomes a dial in your own hand.

How big should the reserve be?

Not big enough to hold a year — that way lies an absurd concrete monster you'd never fill. Big enough to bridge your longest dry gap. Learn your local rainfall month by month and trace the year like a bank balance: in the wet months water flows in faster than you use it and the tank fills; in the dry months nothing comes, so you draw down. Find the deepest that balance dips, and size the reserve to cover it. Too small and you're buying tankers every dry season; too big and you've buried money in concrete that never fills.

Will you catch the rain?

If you have a roof and it rains — yes, wholeheartedly. Rainwater is the cheapest, cleanest large volume you'll ever get: it falls for free and arrives soft and low in minerals, easier to treat than groundwater. Its only fault is timing — it comes in a generous few months and then stops, which is the entire reason the reserve exists. A bigger roof is simply a bigger bucket.

Where else might water come from?

Usually a well or borewell, sometimes a municipal line, sometimes a tanker when all else fails. One quirk catches nearly everyone out: a borewell's usefulness depends on how high the water sits in it, not how deep the hole was drilled. Municipal and tanker water cost money and may simply stop when you need them most — which is exactly why they're the backup, not the plan.

06The quieter truths most people missThe difference between a plan that holds and one that doesn't.Read more

—Greywater is a second supply hiding in your drains.

The water from baths and laundry is only lightly dirty; cleaned modestly, it's perfectly good for flushing and the garden. Reusing it can roughly halve how much fresh water a household needs — in a drought, the distance between comfortable and desperate. Most people pour it straight away. Once plumbed, it works for free forever.

—The toilet is drinking your good water for no reason.

Flushing can be one of your largest uses, and it needs wet water, not clean water. Send greywater to the cisterns and the toilet stops competing with your drinking supply. And there's a bolder move: a dry or composting toilet needs no water at all. Kept as a backup alongside the flush, it removes your single largest water demand on the day the supply runs thin — worth its weight in gold in month eight of a dry year. The flush is a convenience; the dry toilet is the insurance. (This is Sanitation's decision as much as Water's — the same choice seen from two rooms.)

—Storing water isn't the same as storing drinkable water.

The big reserve holds general-purpose water; drinking water is treated on its way to the glass, in the small amounts you actually drink — rather than trying to keep the whole tank hospital-clean. Treat little and often, and treat wisely: what your water needs depends entirely on what a test says is in it. Test first; buy only the treatment your water actually calls for, not the fanciest box on the shelf.

—Gravity is a free servant, and it never has a power cut.

A tank up high feeds your taps with no pump and no electricity — which matters enormously the day the power dies. Build things so at least your survival floor can arrive by gravity and be drawn by hand. And two smaller tanks beat one big one: you can clean or mend one without going dry.

07
A gentle word

Put your water high and clean, and your waste low and far — and nobody's borewell will taste of surprises.

In India someone will raise Vaastu. Much of it is practical wisdom in ceremonial dress: keeping clean water to the north-east happens to line up exactly with keeping your source uphill of and well away from where waste and drainage go — which is precisely what any sanitary engineer would urge. Believe the cosmic version or the plumbing one; you arrive at the same sensible place.

08
How it ties to everything else

Water doesn't sit alone.

It's knotted to its neighbours, and pulling it makes them move. Feel these not as a complication to resent but as leverage: the best moves you'll make solve two problems at once.

Power

The pump that lifts it and the plant that cleans it draw energy — so your water plan quietly writes a line in your power plan. Solve some by hand or by gravity, and you lighten the load in the very next room.

Sanitation

Every litre you flush is both a water cost and a waste to handle. Choosing your toilet and choosing your water are the same decision seen twice.

Food

Dried stores are just weight until water brings them back to dinner. The pantry leans on the tank.

You've just done the thinking. Now let Emberline do the arithmetic.

Tell it about your home — your people, your roof, your rainfall, your well — and it works these considerations into a sized plan: a reserve that bridges your dry gap, the harvesting and reuse that shrink it, and a treatment matched to what's actually in your water.

Fill the Water section →← The 13 systems
© 2026 Emberline·All rights reserved·A planning & education tool, not professional advice.
© 2026 Emberline. All rights reserved.
The Emberline household-continuity methodology, engine, and all written content are the intellectual property of Emberline and may not be copied, resold, or reproduced without written permission.