Two different jobs
A water softener is a tank of resin beads. The beads hold sodium. As water passes through, the resin takes calcium and magnesium out of the water and gives sodium back in exchange. The hardness drops to almost nothing. Every few days the resin fills up, and the unit flushes it with strong brine to reload it with sodium, which is why a softener needs salt. It treats every litre the house uses, at full flow, with no waste except the water used to regenerate.
A reverse osmosis purifier pushes water through a membrane so tight that dissolved ions mostly cannot pass. What comes through is low in everything: calcium, sodium, chloride, nitrate, fluoride, most of the lot. What does not come through goes to drain as reject. It works slowly, on the few litres a day you drink and cook with, and it throws away more water than it makes.
The two are built for different volumes and different purposes. One conditions the water the house uses. The other purifies the water you swallow.
What each removes, and what each leaves
| Question | Softener | RO purifier |
|---|---|---|
| Removes hardness (calcium, magnesium) | Yes, almost completely | Yes, along with everything else |
| Lowers TDS | No. Sodium replaces calcium; the total stays about the same | Yes, by a large fraction |
| Removes bacteria and virus | No | Not on its own; the UV stage does that |
| Removes nitrate, fluoride, arsenic | No | Largely, depending on the membrane and the feed |
| Water treated | Whole house, at full flow | A few litres a day, at the kitchen |
| Water wasted | Only during regeneration | A large share of the feed, every litre |
| Needs | Salt, and resin every few years | Cartridges, a membrane, sometimes a pump |
| Protects the geyser and washing machine | Yes | No |
| Makes water safe to drink | No | Yes, with UV, when the feed calls for it |
The line that surprises most people is the second one. A softener does not lower TDS. It swaps one dissolved thing for another, so a TDS meter reads about the same after the softener as before it. The TDS vs hardness guide goes into why. Anyone who buys a softener because the meter reads high has bought the wrong thing.
The lines after it matter just as much. A softener removes no bacteria, no nitrate, no fluoride. Softened water is conditioned, not purified. Whether the house needs purification is decided by what is in the water, not by its hardness, and the guide to what TDS does not tell you covers the things to check.
Which one you need
Answer two questions. Is the water hard, meaning above the 200 mg/L as CaCO₃ that IS 10500 calls acceptable? And is the drinking water fit to drink without treatment?
Hard, drinking water otherwise fine. Common on piped municipal supplies in hard-rock districts. A softener on the house line fixes the scale, the laundry and the shower. For drinking, choose the purifier by what the water actually needs, which may be UV alone; the UV vs RO guide walks through that decision. Do not fit RO to fix hardness.
High TDS, not especially hard. Coastal groundwater with seawater in it reads high on the meter and low on hardness, because salt is not hardness. A softener does nothing useful here. RO for drinking is the answer, and the house water is left as it is.
Both hard and high in TDS. The usual inland borewell case, and the one where people need both machines. A softener for the house, an RO purifier for drinking, and the softener plumbed ahead of the purifier. That order is not optional. As RO concentrates the feed, the calcium left behind precipitates on the membrane as scale, and on very hard feed it can block a membrane in months. Softened feed keeps the membrane alive. A membrane rated for high-TDS feed, such as the LUXGEN 100 GPD molded membrane, handles the salt; it still wants the calcium taken out first. The high TDS guide and the borewell guide cover this water in detail.
Neither hard nor high in TDS. Then the only question is whether the water is safe, which is a lab test, not a hardness kit.
Can you drink softened water?
Softened water contains more sodium than it did, in proportion to the hardness removed. On moderately hard water the extra is small. On very hard water it is not trivial, and people on a restricted-sodium diet, and anyone making up infant feeds, are usually advised to use an unsoftened or RO-treated tap for drinking. The normal arrangement is a hard-water tap in the kitchen for drinking and cooking, or an RO purifier, with the softener serving everything else. A softener is not a substitute for a purifier, for the reasons in the table: it removes nothing that makes water unsafe.
Where LUXGEN fits, and where it does not
LUXGEN makes RO purifiers and the membranes, cartridges, pumps and housings that go inside them. It does not make a water softener, and this site will not steer you to one. If the answer to your water is a softener, DraQua carries them at draqua.online, and the cost guide will tell you roughly what to budget. If the answer is RO for drinking, the three LUXGEN purifiers are compared on the home page, and the guides here will help you pick the membrane. If the answer is both, buy the softener first.
Questions
Does a water softener lower TDS?
No. A softener exchanges calcium and magnesium for sodium. The hardness falls to nearly zero but the total of dissolved solids stays about the same, so a TDS meter reads roughly what it read before. Only RO, distillation or deionisation bring TDS down.
Can I use RO water instead of a softener?
Not for the house. A domestic RO purifier makes a few litres a day and rejects most of its feed. It cannot supply a shower or a washing machine. RO is for drinking water; a softener is for the water the house uses.
Do I need a softener before my RO purifier?
On very hard feed, yes. As the membrane concentrates the water, calcium precipitates on it as scale and shortens its life sharply. A softener ahead of the purifier removes the calcium first. On moderately hard water inside the IS 10500 limits, a sediment cartridge changed on time is usually enough.