Water Purifier Storage Capacity: How Many Litres Does Your Family Need?

For most Indian homes, a purifier with a 7 to 10 litre tank and a reasonable purification rate covers a family of two to six, because the tank only has to cover peak moments, not the whole day. What decides whether you run short is the purification rate in litres per hour (LPH), not the tank alone. A bigger tank than you need mostly means water standing longer.

How Much Purified Water a Household Uses

Start with what actually goes through the purifier: drinking water, plus water for cooking (rice, dal, tea, kneading dough, rinsing vegetables you eat raw). Bathing, cleaning and washing utensils normally use tap water.

A reasonable planning estimate is about 3 to 4 litres per person per day for drinking, and a similar amount for cooking. That gives roughly 6 to 8 litres per person per day from the purifier. It is a planning figure, not a measurement of your home: hot summers, people who exercise, small children, guests and how much you cook all move it up or down.

Storage vs Purification Rate (LPH)

A storage purifier has two numbers that work together:

• Storage (litres): purified water ready to dispense instantly, the buffer for a sudden demand such as filling bottles before school.
• Purification rate (LPH): how fast the purifier refills that buffer. This is what determines your total daily supply.

Run the arithmetic. A purifier rated at 20 LPH refills an 8-litre tank from empty in about 24 minutes under rated conditions (8 divided by 20 is 0.4 of an hour). Rated output is measured under standard test conditions; higher input TDS, colder water and lower pressure slow it, so allow some margin. Even so, a family of four needing around 30 litres a day only needs the purifier running for about an hour and a half in total, spread across the day.

That is why a “15 litre” or “10 litre” label on its own does not tell you much. A large tank behind a slow purification rate can still run dry on a busy morning, and once it is empty it refills slowly. A moderate tank behind a healthy LPH rarely runs short, because it keeps topping itself up.

Planning Table: Families of 2, 4 and 6

Household	Daily need (planning estimate)	Sensible tank	What to look for
2 people	About 12 to 16 litres	4 to 8 litres	A smaller tank keeps water turning over; LPH is rarely a constraint
4 people	About 24 to 32 litres	7 to 10 litres	A healthy LPH matters more than a bigger tank
6 people	About 36 to 48 litres	8 to 12 litres	Prioritise LPH; consider filling bottles or a jug in the evening for the morning rush

For larger joint families or homes with very high use, check the purification rate carefully and consider a freestanding system with more capacity. For two-person homes, our guide on the best water purifier for a small family or apartment covers space and budget in more depth.

When a Bigger Tank Just Means Stale Water

Purified water is very clean, but it is not meant to sit for days. The longer water stands in a tank, the more time there is for microbes to settle and grow on wet surfaces. A 15-litre tank in a two-person home may hold water that is a day or more old; an 8-litre tank in the same home turns over far more often.

So size the tank to your use, not to the biggest number on the shelf. If you travel often or the purifier goes unused for a few days, drain and refill the tank when you return. Clean it on the service schedule; our guide on how to clean a water purifier at home shows what is involved.

Tankless Purifiers: Pros and Cons

“Water purifier without storage” is a growing search because tankless designs remove the stale-water question entirely: water is purified as you draw it.

• Pros: nothing stands in a tank; a compact body; no tank to clean.
• Cons: flow at the outlet depends entirely on how fast the purifier can purify, so filling a large vessel can feel slower; every glass needs power and water pressure at that moment; there is no reserve during a power cut.

Tankless suits homes with steady power and steady water pressure who draw small amounts often. Storage suits homes with power cuts, irregular supply or big peak demands. Neither is universally better.

Power Cuts and Peak Hours

RO purification needs electricity. When the power goes, a storage purifier keeps giving you what is in the tank and a tankless one gives you nothing. In areas with regular outages, the tank is your backup, which is a good argument for storage, sized sensibly.

Also think about your peak: the morning half hour when bottles, tea and lunch boxes all happen at once. The tank should cover that peak comfortably. Everything after that is the purification rate’s job. For the wider buying checklist, see our water purifier buying guide.

Where Boon Fits

Boon Homie purifies at 20 litres per hour into an 8-litre tank: the combination worked through above, which suits most families of two to six. In-line LED UV treats water before it enters the tank. A patented manual filling feature lets you draw stored, already-purified water by hand during a power cut. It is a wall-mounted RO, ₹21,900 at the time of writing, with free installation by Boon’s own team and a 2-year warranty.

Boon Tap also has an 8-litre tank, sits under the sink with a dedicated faucet on the counter, and is from ₹23,500 at the time of writing.

Where these are not right: very large households with heavy daily use should look at a freestanding system with more capacity. And if you want a fully tankless purifier, neither Homie nor Tap is one. Boon Homie Pro has a smaller 4-litre stainless steel tank and adds instant hot water, but it has no cold water.

Frequently Asked Questions

How many litres of water purifier storage does a family of 4 need?

A tank of around 7 to 10 litres usually works for four people, provided the purifier has a healthy purification rate. A planning estimate of 6 to 8 litres per person per day for drinking and cooking gives about 24 to 32 litres daily. The tank only needs to cover the morning peak; the purification rate supplies the rest across the day.

Is a 10 litre or 15 litre water purifier better?

Not automatically. A bigger tank only helps if your peak demand is larger than a smaller tank can cover. For most homes, purification rate in litres per hour matters more, because it decides how quickly the tank refills. In small households a 15-litre tank can leave water standing longer than necessary, so size the tank to how much you actually use.

What does LPH mean on a water purifier?

LPH means litres per hour, the rate at which the purifier produces purified water under rated test conditions. A 20 LPH purifier can refill an 8-litre tank from empty in about 24 minutes. Real output is slower with higher input TDS, colder water or lower water pressure, so treat the figure as a best case and allow some margin when planning.

Is a water purifier without storage a good idea?

It can be, for homes with reliable power and steady water pressure that draw small amounts often. Tankless designs avoid water standing in a tank, but they give no reserve during a power cut and can feel slow when filling large vessels. Homes with regular outages or busy morning peaks are usually better served by a sensibly sized storage tank.

How long can purified water stay in the purifier tank?

Purified water is best used and replaced within a day or so. The longer it stands, the more time microbes have to settle on wet surfaces. Use the purifier daily, choose a tank sized to your household, and drain and refill it after you have been away for a few days. Have the tank sanitised on the manufacturer’s service schedule.

What size water purifier does a small family of 2 need?

A tank of around 4 to 8 litres is plenty for two people. A planning estimate of 6 to 8 litres per person per day gives about 12 to 16 litres daily, which almost any home RO purifier can produce. A smaller tank is an advantage here, because water is replaced more often and spends less time standing in storage.