Hard Water Filter Cartridge for RO Plants
The Axtron Cation Resin Filter Cartridge is a 10 inch hard water filter for RO plants. It reduces the hardness in your water before it reaches the RO membrane, which protects the membrane and helps it last longer. It's made for homes where the RO plant runs on boring water with very high hardness, the kind that leaves white marks on taps and stains floors. The price is Rs 1,500. You can buy it at our shops in Multan, Lahore and Bahawalpur, or order it with cash on delivery anywhere in Pakistan.
Signs Your Water Has High Hardness
Hardness comes from calcium and magnesium dissolved in water, and it is common in boring (groundwater) supplies. You'll usually see it around the house before you test for it:
- White, chalky marks on taps, showers and fittings
- Stains and a hard layer on bathroom and kitchen floors
- Scale inside kettles and geysers
- An RO membrane that loses water output much sooner than expected
If your RO plant runs on this kind of water, the membrane is taking the full load of that hardness every day.
How the Cation Resin Cartridge Protects Your RO Membrane
The cartridge is filled with cation resin, which takes hardness out of the water as it passes through. By the time the water reaches the RO membrane, much of the hardness has already been removed, so the membrane has less to deal with and lasts longer.
What it does not do: it doesn't lower TDS. Its job is to reduce hardness. The RO membrane still does the main purification and TDS reduction.
How to Install It: Adding a 4th Housing
A standard RO plant has three pre-filter housings. To use the cation resin cartridge, add one extra 10 inch housing and connect it to your RO plant with pipe and fittings. Your plant then has four pre-filter housings in this order:
- PPF sediment filter
- GAC carbon filter
- Cation resin cartridge (this product)
- CTO carbon block filter
After that, the water continues to the RO membrane as normal.
You can buy a 10 inch filter housing with the pipe and fittings from any of our shops. In Multan, Lahore and Bahawalpur, our technicians can fit the extra housing for you.
Specifications
| Brand | Axtron |
| Type | Cation resin filter cartridge |
| What it does | Reduces water hardness |
| Size | 10 inch (fits standard 10 inch housings) |
| Use | RO plants on high-hardness water |
| Position | Between the GAC and CTO stages, in an extra 10 inch housing |
| Refillable | No. Replace the whole cartridge. |
| Price | Rs 1,500 |
When to Replace It
There is no fixed life for this cartridge. How long it works depends on how hard your water is and how much water your RO plant uses. Hard water uses up the resin faster.
The reliable way to know is to test your water:
- After installing the cartridge, test the water's hardness to see how much it has dropped.
- Test again every 10 to 15 days.
- When the hardness starts rising again, the resin is used up, so replace the cartridge.
The cartridge cannot be refilled. Replace the whole cartridge each time.
Keep your other pre-filters on schedule too. From our field experience, change the PPF filter every 15–30 days and the GAC and CTO every 3 months at most.
Water Hardness in Multan and South Punjab
Water hardness is commonly classified by its calcium carbonate content: up to 60 mg/L is soft, 61–120 is moderately hard, 121–180 is hard, and above 180 mg/L is very hard. Groundwater in parts of Pakistan sits well into the "very hard" range:
- Multan: a 2025 study of groundwater from sites across Multan city found total hardness between 306 and 543 mg/L. Every site tested was in the very hard range.
- Bahawalpur: a 2024 study of groundwater in Bahawalpur district found calcium up to 110 mg/L and magnesium up to 73 mg/L. These are the two minerals that cause hardness.
- Across Pakistan: the PCRWR's study of underground water in 29 major cities, reported in 2021, listed hardness among the main problems, alongside TDS, arsenic and bacteria.
Hardness can differ a lot even within the same city, depending on the area and the depth of the boring. If your taps and floors show white scale, get your water tested to see how hard it is before choosing a solution.
Cation Resin Cartridge or Anti Scalant Cartridge?
Both help protect the RO membrane from hard water, but they work differently:
| Cation Resin Cartridge | Anti Scalant Cartridge | |
|---|---|---|
| What it does | Reduces hardness in the water | Stops hardness minerals from forming scale |
| Best for | Water with very high hardness | Hard water where scale is the main concern |
| Where it goes | Extra housing between GAC and CTO | After the solenoid valve, before the pump |
For RO plants on water where hardness is at its peak, the cation resin cartridge is the stronger choice because it takes hardness out of the water. See the anti scalant cartridge for comparison.
For semi commercial RO plants with slim housings, see the 20 inch slim cation resin cartridge.
Buy Hard Water Filter Cartridge in Multan, Lahore and Bahawalpur
Visit any Axtron shop to buy the cartridge with a housing and fittings, or to book installation. Our head office is in Multan.
Multan (Head Office)
5FP4+CXF, Akbar Road, Tipu Sultan Colony, Multan 60000
0302-1635555 · 0300-4773040 · 061-4544442
Lahore
91-A Feroz Pur Road, Lahore
0304-8205829 · 042-37502222
Bahawalpur
Opposite Sadiq Public School, Ahmad Pur East Road, Bahawalpur
0302-7401250 · 062-2201005
Timings: Saturday to Thursday, 10:00 AM – 7:00 PM. Friday closed.
Email: info@axtronpakistan.com
In Multan, Lahore and Bahawalpur, our own technicians can add the extra housing and fit the cartridge. In other cities, we can connect you with an independent local technician on WhatsApp, who quotes and collects the charges directly. We deliver across Pakistan with cash on delivery, and installation videos are on our Facebook and Instagram pages. In Multan, see our water filter shop in Multan page. In Lahore, see RO plant in Lahore.
Frequently Asked Questions
What does a cation resin filter do?
It reduces the hardness in water before it reaches the RO membrane, which protects the membrane and helps it last longer.
Can I use this hard water filter without an RO plant?
No. This cartridge is for RO plants only, where the water has very high hardness.
Where do I fit the cation resin cartridge in my RO plant?
Add one extra 10 inch housing with pipe and fittings. The order becomes PPF, GAC, cation resin, CTO, then the RO membrane.
Does it reduce TDS?
No. It reduces hardness only. The RO membrane reduces TDS.
How long does the cation resin cartridge last?
There's no fixed life. It depends on your water's hardness and how much water you use. Test your water every 10 to 15 days, and replace the cartridge when hardness starts rising again.
Can the resin be refilled?
No. When the resin is used up, replace the whole cartridge.
Is the water in Multan hard?
Often, yes. A 2025 study of Multan groundwater found total hardness between 306 and 543 mg/L at the sites tested, which is in the very hard range. Levels vary by area and boring depth, so testing your own water is the best guide.
What is the price of the cation resin cartridge?
The Axtron 10 inch cation resin filter cartridge costs Rs 1,500.
Where can I buy a hard water filter cartridge in Multan?
At the Axtron head office on Akbar Road, Tipu Sultan Colony, Multan, open Saturday to Thursday, 10 AM to 7 PM. Call 0302-1635555 for the cartridge, the extra housing and installation.
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