Aptera AlkaMag Inline Alkaline & Remineralization Filter
A post-RO polishing cartridge that puts calcium and magnesium back into reverse-osmosis water and lifts its pH. A sealed 2.5" × 12" inline body with 1/4" FPT ports that installs on the product-water line, ahead of your storage tank.
Reverse osmosis does its job almost too well — it strips out nearly everything, including the calcium and magnesium that give water its body and a neutral pH. The result is often water that tastes flat and sits slightly acidic. The Puregen Aptera AlkaMag is a sealed inline cartridge that corrects that on the way to the tank. Its media bed dissolves a small, controlled amount of calcium carbonate (calcite) and magnesium (corosex) back into the permeate, raising pH by roughly 1 to 3 points toward 8.0+ and restoring a clean mineral taste. It also carries a neodymium magnetic module and a stack of mineral and ceramic medias the manufacturer characterizes as emitting far-infrared energy and negative ions and lowering the water's ORP. Because it works by contact time, it is designed to run at the RO membrane's slow production rate — installed on the permeate line between the membrane and the holding tank. It is a polishing stage, not a standalone filter.
Key Performance Metrics
Install on the Permeate Line, Before the Tank
This filter is meant for one spot: the product-water line running from the outlet of your RO membrane to your storage tank. That is where the water is already purified and moving at the membrane's slow production rate, which is exactly what the media needs — the water has to sit in contact with the calcite, corosex, and mineral beds long enough to pick up minerals and shift pH. Puregen rates it for RO systems producing up to 50 GPD. Run it faster than its 0.025–0.035 GPM design flow and you get less mineral pickup and less pH lift.
This is not a standalone filter. It does not remove sediment, chlorine, or contaminants and is not built to take full line pressure or municipal tap water. It polishes water that has already been through reverse osmosis. Plumb it after the membrane, never on the feed side.
Construction & Media
| Part Number | APTERA-INLINE |
| Filter Type | Sealed inline alkaline / remineralization cartridge for post-RO use |
| Primary Media | Calcium carbonate (calcite) and magnesium oxide (corosex) with mineral beads — the active blend that raises pH and reintroduces calcium and magnesium |
| Additional Media | Multi-stage bed that also includes a neodymium magnetic module, quartz, and tourmaline / Pi / negative-ion ceramics. The manufacturer characterizes these as emitting far-infrared rays and negative ions and lowering ORP. |
| pH Effect | Raises pH by approximately 1 to 3 points, toward 8.0 or higher, depending on source water and flow rate |
| ORP | Manufacturer states the media lowers the water's oxidation-reduction potential (redox potential) |
| Dimensions | 2.5" outer diameter × 12" length |
| Connections | 1/4" FPT (female NPT) inlet and outlet — observe the flow-direction arrow |
| Design Flow Rate | 0.025 – 0.035 GPM (contact-time limited; not a high-flow filter) |
| Rated Capacity | 500 – 1,000 gallons — typically 6 to 12 months, varies with water chemistry and use |
| Maximum Pressure | 80 PSI |
| Maximum Temperature | 90°F |
| Application | Reverse-osmosis post-filter, for systems producing up to 50 GPD |
| Important | Cannot be used as a standalone water filter — polishing stage only |
Why Add It to an RO System
Restores What RO Removes
Reverse osmosis takes out calcium and magnesium along with the contaminants. This bed dissolves a measured amount back in, so the water is not effectively mineral-free.
Raises Acidic Permeate
RO water tends to sit slightly acidic. The calcite and corosex media lift pH by roughly 1 to 3 points toward a neutral-to-mild-alkaline range.
Improves the Taste
A trace of dissolved minerals is what makes water taste "round" instead of flat. Most people notice the difference in RO water right away.
Sealed, No-Mess Body
A fully sealed inline cartridge — no housing to open, no loose media to pour. When it is spent, you swap the whole unit.
Neodymium Magnetic Module
The cartridge begins with a high-strength neodymium magnetic module, part of the Aptera multi-stage media design.
Standard 1/4" Fit
Threaded 1/4" FPT ports accept common John Guest–style stems and elbows, so it drops into virtually any 1/4" RO line.
Getting Set Up
- Turn off the RO feed water and open the faucet to relieve pressure. Locate the product-water tube that runs from the membrane housing outlet toward the storage tank — this is where the filter goes.
- Thread your 1/4" fittings into both FPT ports (John Guest stem or elbow fittings are typical). Use a wrap of PTFE tape on the threads and do not overtighten the plastic ports.
- Cut the permeate line and connect the filter with the flow-direction arrow pointing toward the tank. Secure the body with a mounting clip so it is not hanging on the tubing.
- Turn the feed water back on, check every connection for leaks, and let the system fill. Drain the first one or two tank-fills to flush any media fines before drinking.
- Plan to replace the cartridge every 6 to 12 months, or at 500–1,000 gallons — sooner if you notice the mineral taste or pH lift falling off.
Slower is better here. Unlike most filters, low flow is a feature — the water needs contact time with the media to gain minerals and pH. That is why it belongs on the membrane's slow permeate line and not anywhere the water moves quickly. If your RO already has its own remineralizing stage, add this only if you want a further pH boost.
Where the Aptera AlkaMag Fits
The AlkaMag inline works as an add-on to virtually any under-sink reverse-osmosis system producing 50 GPD or less, and is a straightforward upgrade for anyone whose RO water tastes flat or reads acidic on a pH test. Because it uses standard 1/4" FPT connections, it adapts to the 1/4" tubing on nearly every residential RO. It is a drinking-water polishing stage — pair it with a proper sediment/carbon/RO train, not in place of one. If your system uses a standard 10" filter housing rather than an inline post-filter, the same AlkaMag media is also offered as the cartridge-style Aptera AlkaMag (APTERA-2510), which drops into a 2.5" × 10" housing.
Ships from California
Stocked in Santa Ana and shipped the same business day on orders placed before cut-off.
Genuine Puregen Aptera
The authentic Aptera AlkaMag inline cartridge — not a rebranded substitute.
System Help
Not sure where it goes on your RO, or which post-filter you need? Call (877) 541-6603 and we will walk your system with you.
