RO membrane
Stage 4 — the core: brings TDS down to its lowest reading.
Cartridge prices are quoted on request — they move with each shipment, and we will not publish a number that is stale within weeks. We confirm it before any commitment, or it sits inside the annual service contract at a fixed price.
What this stage does
The reverse-osmosis membrane — the heart of the system. Its pores are too fine for dissolved salts to pass, so most are separated out and sent to drain with the reject water. This is what actually lowers your TDS reading; the other stages protect it or polish what comes after it.
How you know it is overdue
- Your TDS reading climbs above the number we recorded at installation
- The tank fills very slowly
- The water starts tasting like tap water again
Why a range and not one number?
Because what uses a cartridge up is the volume of water passing through it and what that water carries — not the calendar. A household of six gets through one faster than a household of two, and a tank collecting more sand shortens it further. We write the reading down at every visit, so by the second or third we know your home's actual rhythm instead of guessing.
Fits these systems
If your system is on this list, this is the right cartridge.
The rest of the set — RO kitchen filter cartridges
- PP sediment 5µEvery 4–6 months
- GAC carbonEvery 4–6 months
- CTO carbon blockEvery 4–6 months
- Post-carbon polishEvery 4–6 months
- Alkaline cartridgeEvery 24 months
- Mineral cartridgeEvery 24 months