What GPD really means
GPD is gallons per day — US gallons, 3.785 litres each. So 80 GPD is about 303 litres a day and 100 GPD about 378. Those are datasheet figures, measured at a fixed test pressure, with 25 °C water and a low-salt test solution.
An Indian kitchen meets none of those conditions. The booster pump in a domestic purifier delivers less pressure than the test rig. Borewell water in winter can be well under 25 °C, and cold water passes through the membrane more slowly. Higher feed TDS raises osmotic pressure, which eats into the pressure that actually pushes water through. The result: a “100 GPD” membrane in a real home makes a good deal less than 378 litres, and the shortfall grows with TDS.
That does not make the rating useless. It is a fair way to compare two membranes with each other. It is not a promise of what your tank will fill at.
The three LUXGEN membranes
| Specification | 80 GPDLUX-RO-80 | 100 GPDLUX-RO-100 | 100 GPD MoldedLUX-RO-100M |
|---|---|---|---|
| Rated output | 80 GPD (~303 L/day) | 100 GPD (~378 L/day) | 100 GPD (~378 L/day) |
| Element | TFC | TFC | TFC, fully molded |
| Format | 1812 (1.8″ × 12″) | 1812 (1.8″ × 12″) | One-piece molded body |
| Fits | Most domestic RO | Most domestic RO | Domestic RO with a pump to match |
| Max feed TDS | Ordinary supply; move to molded above 2000 ppm | Ordinary supply; move to molded above 2000 ppm | 3000 ppm |
| Salt rejection | — | — | 96–98% |
| Price | ₹650 | ₹800 | ₹900 |
| Order | View on DraQua | View on DraQua | View on DraQua |
A 100 GPD membrane needs a pump that can drive it
This is the point most people miss. A 100 GPD membrane is built to pass more water at the same pressure. It only does that if the pressure is there.
Fit a 100 GPD membrane behind a pump meant for a 50 or 80 GPD system and you get the opposite of what you paid for. The pump cannot hold pressure across the larger element, the net driving pressure falls, and the membrane sends a bigger share of the feed down the reject line. Output goes down, not up, and the drain runs more.
The matching pump in the LUXGEN range is the 100 GPD RO Booster Pump, LUX-PUMP-100: 24 V DC, 140 PSI maximum, 1.5 LPM, about 1.10 A draw, 36 mm armature. ₹1,299. If your purifier’s existing pump is a 100 GPD unit in good health, you do not need a new one. If it is a smaller pump, or it is a few years old and noisy, budget for the pump alongside the membrane. The two are a pair.
Rule of thumb
Pump first, then membrane. An 80 GPD membrane on a weak pump still works. A 100 GPD membrane on a weak pump works worse than the 80 it replaced.
Molded versus standard
A standard 1812 membrane is a rolled element inside a plastic shell with glued end caps. A fully molded membrane forms the shell around the element in one piece. No seams, no glue line, nothing to weep under pressure and nothing to open, refill with a cheaper element and re-seal. That is what leak-proof and tamper-resistant means in practice.
The molded LUX-RO-100M is also the only membrane in the range rated for feed up to 3000 ppm, with 96–98% salt rejection. Above 2000 ppm feed it is the one to use — not because the standard membrane will not work on day one, but because it will not last. The TDS chart covers what else high-TDS water needs.
Below 2000 ppm, the molded membrane is a ₹100 premium over the standard 100 GPD for the sealed construction. Worth it if you have had a membrane leak before. Not essential otherwise.
The recovery trade-off, honestly
Every RO membrane splits feed water into permeate, which you drink, and reject, which goes to the drain. A domestic unit typically sends two to three litres to drain for every litre it purifies. Push recovery higher to save water and the salts concentrate in less reject, which pushes the membrane towards scaling. Push it lower for membrane life and you waste more water. A 100 GPD membrane makes more permeate per hour; it does not change this ratio much. If the reject volume bothers you, collect it. It is fine for mopping and for plants that tolerate the salt.
So which one?
- Standard domestic purifier, standard pump, feed under 2000 ppm: LUX-RO-80, ₹650. It is the cheaper option and it is the right one.
- Large household, the tank empties before it refills, and a 100 GPD pump already fitted: LUX-RO-100, ₹800.
- Feed above 2000 ppm, or a history of leaking membranes: LUX-RO-100M, ₹900, with LUX-PUMP-100 if the existing pump is not up to it.
Every membrane and the pump are listed with full specifications in the full range. If you are choosing a whole purifier rather than a membrane, start with the purifier comparison.
Questions
Will a 100 GPD membrane make my purifier faster?
Only if the pump can drive it. With a 100 GPD pump such as the LUX-PUMP-100, yes: more permeate per hour. With a smaller or tired pump, output falls and more water goes to the drain. Check the pump before buying the membrane.
What is the difference between the molded and the standard 100 GPD membrane?
Same 100 GPD rating and the same TFC element. The molded LUX-RO-100M has a one-piece body with no glued seams, so it cannot leak or be tampered with, and it is rated for feed up to 3000 ppm with 96 to 98 percent salt rejection. The standard LUX-RO-100 is ₹800; the molded membrane is ₹900.
Does a bigger membrane waste more water?
Not in proportion. The reject-to-permeate ratio is set mostly by pressure and feed TDS, not by the membrane rating. A 100 GPD membrane produces more of both per hour; the ratio stays roughly the same.