RO water tastes bad? Five tastes, five causes, and which of them cost nothing to fix.

Name the taste first

Purified water should taste of very little. When it tastes of something, the something is a clue, and the tastes below each point at a different part of the purifier. Read down the left column, find yours, and go to that section.

Chlorine: the carbon is spent

Municipal water is chlorinated on purpose, and the carbon cartridge in the purifier exists to take the chlorine out. Coconut-shell carbon holds a fixed amount and then holds no more. When the smell of a swimming pool arrives in the purified water, the carbon is full, and its interval of up to twelve months has been reached whatever the calendar says.

The taste is the least of it. The RO membrane behind the carbon is a thin polyamide film, and chlorine attacks polyamide. A membrane that has been fed chlorinated water through a spent carbon cartridge loses rejection and does not get it back. So the day you taste chlorine is the day to change the carbon, not the week after. The Universal-Fit carbon cartridge is ₹220 and the Branded-Fit ₹250; the fit guide tells you which your housing takes. Change the ₹190 sediment cartridge at the same time if it is near its own interval, since silt that got past it is one reason a carbon block gives up early.

Some purifiers also carry a small inline carbon cartridge after the tank to polish the taste. It is not a part in the LUXGEN range and its price depends on the make; change it on the same twelve-month rhythm.

Flat: the membrane is doing its job

This one is not a fault. A working RO membrane removes most of what is dissolved in the feed, and what is dissolved is what water tastes of. Calcium and magnesium give water body; bicarbonate gives it a faint sweetness. Take them out and water at 10 or 20 ppm tastes thin, flat and to some people slightly sour. A new membrane makes this more noticeable, not less, because it rejects best on its first day.

The fix is a setting, if your purifier has it. A TDS controller lets a little filtered water bypass the membrane and rejoin the output, which puts some mineral and the taste back; the Aura and the Royale Copper have one, the Curve does not. Open it a quarter turn, run a tankful, taste, and stop where it tastes right, then read the output with a meter and write the number down so you know what normal is from now on. A mineral cartridge does the same job on a purifier with no controller. The low TDS guide goes through whether stripped water is a health question at all, and the RO output TDS guide what the output reading should be.

One trap: flat and salty are opposites. Flat with a new membrane is over-filtration. Salty with an old one is under-filtration, and that is two sections down.

Metallic: three places it comes from

A metallic or coppery edge has three usual sources, and they are easy to tell apart.

A copper stage. Purifiers with a copper cartridge, such as the Royale Copper, add a trace of copper to the output on purpose, and a fresh copper cartridge, or a tank that has stood overnight in contact with it, can taste of it. Run the first tankful after a cartridge change to drain, and draw the morning's first water off before drinking it. If the taste is strong and constant, the copper cartridge is dosing too much; its replacement is a part from the purifier's own maker, not a LUXGEN spare; for a LUXGEN purifier, the installation and service page gives the route.

Iron in the feed. Borewell water often carries dissolved iron and manganese. The sediment cartridge catches the rust particles but not what is dissolved, and a tired membrane lets more of it through. An orange tint in the pre-filter bowl and a metallic taste at the tap together point at the feed: get it lab-tested once, which the what TDS does not tell you guide explains, and check the membrane with the meter test below.

The pipe before the purifier. Old galvanised plumbing sheds iron and zinc, worst after water has stood in it overnight. The purifier removes most of it, at the price of a sediment cartridge that browns faster. If the cartridge is orange in weeks rather than months, the pipe is the reason, and a wall-mounted pre-filter bowl ahead of the purifier is the cheap protection.

Salty or chalky: the membrane is letting the feed through

Water that has started to taste of the tap, salty on a coastal supply or chalky on a hard borewell, is a membrane passing more than it should. Confirm it with a meter rather than a tongue. Read the feed and the output with the TDS controller shut. A healthy membrane leaves a few percent of the feed; when the output has roughly doubled from the reading taken on the day the membrane went in, it is done. A sudden jump to near the feed reading is not the membrane but a bypass: a controller left wide open, or a membrane seal not seated. The membrane replacement guide has the full test and the causes.

The replacements are the 80 GPD at ₹650, the 100 GPD at ₹800 behind a pump rated for it, and the molded high-TDS membrane at ₹900 for feed above 2000 ppm. If the membrane died in under a year, the carbon cartridge was probably spent and chlorine did the damage; change both.

Stale or musty: the tank

Purified water has nothing in it to keep it fresh. Left in a storage tank in a warm kitchen for a few days, it picks up a taste from the tank walls and, given long enough, a film grows on them. Water that tastes fine in the evening and musty after a weekend away is this, and it is the one fault on the page that costs nothing but ten minutes. It is also why the Curve keeps its tank under UV.

• After any gap of two days or more, draw the whole tank off and let it refill before drinking.
• Every three months, unplug the machine, close the inlet, empty the tank, wipe it out, rinse and refill. The service vs DIY guide lists this as a homeowner job, and it is.
• If the smell is in the cabinet, not the water, look at the drain line. A reject line pushed below the water in a sink trap lets the drain smell back up it. The installation checklist shows the air gap that stops it.

An earthy taste in the feed itself, common from reservoirs in summer, is the carbon stage's job, and if it gets through, the carbon is due. A UV lamp that has failed leaves the tank unprotected; the lamp and its ballast are mains voltage and a technician's part, and the price depends on the make.

Which fixes are yours

The carbon and sediment swap, the controller setting, the tank clean and the first-tankful flush are all homeowner jobs with the machine unplugged and the inlet closed. The membrane is doable with care. The copper cartridge, the UV lamp and anything with a wire on it are for a technician, because they sit at mains voltage in a wet cabinet. One rule sits above all of these: water that smells of drains or sewage is not a taste problem, it is contamination from a backflow or a failed seal, and the purifier should not be used until someone has found the cause.