So Pure CTO Activated Carbon Block for Domestic RO Water Filters
The So Pure CTO is a 10 inch activated carbon block cartridge for the 3rd stage of a domestic RO water filter. It sits after the sediment filter and the GAC filter, and it is the last pre-filter before the RO membrane. It removes the chlorine, organic compounds and odour-causing gases the earlier stages leave behind, and it protects the membrane from clogging residues.
So Pure is one of the cartridge brands Axtron Pakistan supplies alongside the Axtron, Classic Pure and Hi-Tech ranges. The cartridge is a standard 10 inch size, so it fits almost every domestic RO plant in Pakistan, whatever the brand.
What Is Printed on the So Pure CTO Label
These details come directly from the product label.
Features (as printed)
- Removes chlorine, surplus organic compounds and gases causing odour from water
- Protects RO membranes from clogging residues
Specifications (as printed)
- Compositions: coal and dechlorination material
- Maximum flow: 100 L/H
- Use pressure: 5 bars
Other Label Details
- Product: CTO
- Note: wash (flush) before water goes into the RO membrane
- Markings printed on the label: NSF and Water Quality Association member logos
- Brand line: “Water at its best”
Why “Wash Before Water Goes Into the RO Membrane” Matters
A new carbon block can release fine black carbon dust. After fitting the cartridge, let water run through it to drain for a few minutes until it comes out clear, before it reaches the membrane. This keeps carbon fines off the membrane surface.
What CTO Means and How the Carbon Block Works
CTO stands for Chlorine, Taste and Odour. Unlike a GAC filter, which holds loose carbon granules, a CTO is carbon compressed into a solid block. Water passes slowly through a dense carbon wall, giving a finer, more even treatment. That is why the CTO is placed right before the membrane, as the final pre-filter stage.
Where the So Pure CTO Sits in Your RO Plant
- PPF sediment filter: removes rust, sand and silt. See the So Pure 1 micron PPF, 0.3 micron PPF or 5 micron PPF.
- GAC filter: removes most of the chlorine and smell.
- CTO carbon block (this product): second carbon stage; membrane protection.
- RO membrane: the main purification stage.
- Post-membrane stages: post carbon, mineral, nano silver, alkaline or others. These can be changed or rearranged to suit your water quality and needs.
So Pure CTO Specifications
| Feature | Detail |
|---|---|
| Brand | So Pure |
| Product type | CTO activated carbon block |
| Stage | 3rd stage (after PPF and GAC, before the RO membrane) |
| Size | 10 inch standard |
| Compatibility | All standard 10 inch housings in domestic RO plants |
| Composition (label) | Coal and dechlorination material |
| Maximum flow (label) | 100 L/H |
| Use pressure (label) | 5 bars |
| Removes (label) | Chlorine, surplus organic compounds, odour-causing gases |
| Replacement | Every 3 months at most |
So Pure CTO vs Other CTO Filters at Axtron
| CTO | Made in | Composition (label) | Max Flow / Pressure (label) |
|---|---|---|---|
| So Pure CTO (this product) | Not printed on the label | Coal, dechlorination material | 100 L/H / 5 bar |
| Hi-Tech Vietnam CTO | Vietnam | Coal, dechlorination material | 100 L/H / 5 bar |
| Axtron Vietnam CTO | Vietnam | See product page | See product page |
| Classic Pure Taiwan CTO | Taiwan | See product page | See product page |
All four are 10 inch carbon blocks for the 3rd stage and fit the same housing. All should be replaced every 3 months at most.
When to Replace the So Pure CTO
From our field experience servicing RO plants:
- Replace the CTO every 3 months at most. Once the carbon is used up, it stops removing chlorine and can start giving the water a smell.
- Change the GAC at the same time. It follows the same 3-month cycle.
- Change the PPF every 15–30 days, or when it turns fully brown or dark. A late PPF change sends dirt into the carbon stages and shortens their life.
- RO plant left unused for some time? Replace all cartridges before using it again. Stale water inside the housings causes smell, and dried cartridges don’t perform properly.
Fresh pre-filters on time help the RO membrane last its normal life of about 1 year. Late pre-filter changes, high TDS and long running hours shorten it.
How to Replace the CTO Filter
- Close the water inlet and switch off the RO plant.
- Open the faucet to release pressure.
- Unscrew the 3rd stage housing with a housing spanner.
- Remove the old cartridge and wash the inside of the housing.
- Check that the O-ring is seated properly, then fit the new So Pure CTO.
- Flush water to drain until it runs clear before it goes to the membrane, as the label advises.
Who Should Use the So Pure CTO
- Homes with a domestic RO plant that uses standard 10 inch housings
- Homes on chlorinated tap water or bore water with a smell
- Anyone doing the regular 3-month pre-filter change
A carbon block does not reduce hardness. In areas with very hard bore water, such as many parts of Multan and South Punjab, ask us about adding a cation resin softening cartridge to protect the membrane.
For a full 3-month change in one order, see the Axtron RO filter set for 3 months or the Classic Pure RO filter set. All cartridges are listed under domestic filters.
Buy the So Pure CTO in Multan, Lahore, Bahawalpur and Across Pakistan
You can buy the So Pure CTO at any Axtron branch or order online with cash on delivery anywhere in Pakistan.
Multan (Head Office)
5FP4+CXF, Akbar Road, Tipu Sultan Colony, Multan 60000
Phone: 0302-1635555 · 0300-4773040 · 061-4544442
Lahore
91-A Feroz Pur Road, Lahore
Phone: 0304-8205829 · 042-37502222
Bahawalpur
Opposite Sadiq Public School, Ahmad Pur East Road, Bahawalpur
Phone: 0302-7401250 · 062-2201005
Contact
Timings: Saturday to Thursday, 10:00 AM – 7:00 PM (Friday closed)
Email: info@axtronpakistan.com
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Installation and service
- Multan, Lahore and Bahawalpur: Axtron’s own technicians can change your filters (service charges are paid to Axtron).
- Other cities: we connect you on WhatsApp with an independent local technician. The technician quotes and collects payment directly. They are not Axtron staff, and Axtron is not responsible for their work.
Looking for a complete system? See our water filter in Multan and RO plant in Lahore pages.
Frequently Asked Questions
What does the So Pure CTO remove?
As printed on the label, it removes chlorine, surplus organic compounds and the gases that cause odour, and protects the RO membrane from clogging residues.
What are the So Pure CTO specifications?
The label lists coal and dechlorination material as the composition, a maximum flow of 100 L/H and a use pressure of 5 bars. It is a 10 inch carbon block.
Which stage is the CTO installed in?
The 3rd stage, after the PPF sediment filter and the GAC filter, just before the RO membrane.
How often should I replace the So Pure CTO?
Every 3 months at most, together with the GAC. Old carbon stops working and can make the water smell.
Why does the label say to wash it before water goes into the membrane?
New carbon blocks release fine carbon dust. Run water through the new cartridge to drain until it comes out clear. This keeps the dust off the membrane.
Will it fit my RO plant?
Yes, if your RO plant uses standard 10 inch housings, as almost all domestic RO plants in Pakistan do.
Where can I buy the So Pure CTO in Multan?
At our head office on Akbar Road, Tipu Sultan Colony, Multan. Call 0302-1635555 or 061-4544442. Our Multan technicians can also fit it at your home.
Do you deliver to Lahore, Karachi and other cities?
Yes. We deliver across Pakistan with cash on delivery. In Lahore you can also visit our Feroz Pur Road branch.
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