How to actually choose a purifier, brand aside

Most people searching for a purifier type a comparison or a budget ceiling into the search box — "best purifier under ₹15,000" — because that's the shorthand the market has trained them to use. But two units at the same price point are usually built from the same handful of parts, arranged differently: a membrane stack, a pump, a tank or no tank, a housing that mounts one of three ways. The differences that actually change how the thing behaves in your kitchen for the next few years are structural, not cosmetic.

Three decisions do almost all the work: how much water it needs to supply on demand, whether that water sits in a tank or gets made fresh each time you draw it, and where the unit physically lives. Get those right for your household and almost any competently built purifier at that spec will serve you fine. Get them wrong and no amount of brand loyalty fixes it.

How much water you're actually sizing for

India's own water-supply planning code, IS 1172:1993, is the reference most sizing advice traces back to, and it puts drinking-and-cooking needs at roughly 5–10 litres per person per day. Sources differ on the split — some allocate 5 litres to drinking and 5 to cooking, others fold cooking into a single 7-litre drinking allowance — but they land in the same band. Treat it as a floor: heat, activity, and personal habit push real consumption higher, and the code was written to plan municipal supply, not to cap what one household drinks.

A purifier doesn't need to hold a full day's water — just enough to cover when you actually draw it: the morning rush, then meal prep. That's what tank size and flow rate (LPH, litres per hour) size for. The bands below sit a little above the code's floor, closer to 8–10 litres a person a day, since households rarely stop exactly at the minimum:

• 1–2 people: roughly 8–20 litres/day. A compact 5–6 litre tank, or a modest-flow tankless unit, comfortably keeps pace.
• 3–4 people: roughly 24–40 litres/day. This is the bracket most purifiers on the market are actually built around — a 7–8 litre tank paired with a 10–12 LPH flow rate.
• 5–6+ people, or households that host often: 40–60+ litres/day. Look at 10–12 litre tanks or 12–15+ LPH tankless output, or plan on more frequent refill cycles.

Storage tank or tankless: what each one actually trades away

A storage tank purifies water in advance and holds it, ready to pour — useful where power cuts are frequent or pressure is low and inconsistent, since you're drawing from water already treated rather than asking the unit to perform on demand. The cost: stored water sits. Left for days, or in a tank nobody's cleaned in months, it becomes exactly the standing water where algae, biofilm, and occasionally bacteria regrow what the purifier just removed — invisible from outside the tank.

A tankless system (also sold as "non-storage" or "direct-flow") purifies water only at the moment you draw it, so nothing sits ageing between uses — every glass is freshly made. The trade-off runs the other way: it needs continuous, adequate power and pressure right when you want water, with no buffer if either drops. In a power cut, a tank purifier still has whatever's stored; a tankless one has nothing until supply returns.

If outages or pressure drops are routine where you live, that alone tips the decision toward a tank — sized to bridge the gap, not to sit unused. If supply is steady, tankless removes an entire maintenance task: nothing to clean, nothing to disinfect, no stagnant water to think about, and a noticeably smaller footprint.

Either way, a tank in regular use needs cleaning every three to six months, sooner if it's sat idle a week or more — idle time is when growth gets a head start.

Wall-mounted, under-sink, or countertop

Mounting is mostly a plumbing-and-space decision, but it also decides how easy the unit is to live with day to day.

Wall-mounted units hang above or beside the sink and tap into the existing line with minimal plumbing — no cabinet cutting, no dedicated line. They stay visible, which some kitchens mind and others don't, but that cuts both ways: filters sit in the open, so replacing them takes minutes, not a service call.

Under-sink units install inside the cabinet, out of sight, feeding a small tap on the counter. They tend to support larger tanks and steadier pressure, plumbed into a dedicated line rather than tapped off an existing one — but that means professional installation, and once in, it isn't casually relocated. Filter changes mean working inside a cabinet, sometimes tight enough to need a technician anyway.

Countertop units need no plumbing in their simplest form — fill a reservoir manually, or connect a single line — the practical option for rented homes or kitchens where drilling isn't allowed. The trade-off is counter space and smaller tanks, since there's no cabinet or wall to bear the unit's weight.

What "budget under ₹X" searches are actually asking

Nobody typing that query actually wants the cheapest box labelled "water purifier" — they want to know which features are worth paying for and which are markup. Three things reliably move the price, whatever name is on the unit:

• RO+UV+UF combined costs more than UV or UF alone, since RO adds a semi-permeable membrane and a pump strong enough to force water through it — hardware a UV/UF-only unit doesn't carry. It's worth paying for only if your water's TDS (total dissolved solids — the dissolved salts and minerals in it, in mg/L) or source actually needs RO. BIS treats 500 mg/L as the acceptable limit for drinking water; below that, UV or UF alone typically suffices, so on already-low-TDS municipal supply, RO is cost solving a problem you don't have.
• A larger storage tank costs more: more housing material, sometimes a second pump to refill it faster. It's worth it only if your household's peak-hour demand genuinely needs the extra buffer.
• Mineraliser, alkaline, or copper cartridges cost more and add an ongoing replacement expense on top of a genuinely debatable benefit — what they reintroduce is marginal next to what an ordinary diet already supplies.

Matching those three to what your water and household need is the whole "budget" decision. Once capacity, storage type, and mounting are settled, comparing options within that spec is close to a coin toss — service network and warranty terms decide more than any real performance gap.