Reusable AISI 304 Steel Casing
The stainless steel housing is engineered to last a decade or more. Backed by a full 10-year warranty, it won't rust, leach, or degrade.
Independently Lab Tested
10-Year Steel Casing Warranty
Aluminum-Free & Non-Toxic
Ships from Our U.S. Warehouse
Refillable, Zero-Waste Design
Product details
Technical Specifications
Material
AISI 304 stainless steel — rust-resistant and non-leaching
Capacity
Up to 1,060 gallons per pair
Compatibility
Phoenix Gravity Carbon Filter Elements and Black Berkey® elements
How It Works
Works in tandem with your primary filter. This is an add-on, not a standalone filter.
Composition
FluoRid — activated carbon blend + proprietary fluoride-reduction media
Warranty
10-year coverage on defects in materials or performance
Fluoride Reduction
95%+ from drinking water
The science behind it
How POSTreat Steel Filters Your Water
POSTreat Steel Filter works as a second-stage post-filter, attached beneath your primary carbon filter elements in the lower chamber — no plumbing, no electricity, no specialist tools.
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Step 01
Fill Upper Chamber
Pour tap water into the upper stainless steel chamber. No electricity or pressure required — gravity does the work.
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Step 02
Carbon Filtration
Activated coconut-shell carbon elements remove 99.9% of chlorine, heavy metals, microplastics, PFAS, and pharmaceutical residues.
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Step 03
POSTreat Steel Filter Stage
Prefiltered water flows through our proprietary FluoRid media inside the AISI 304 steel casing — capturing fluoride with 95%+ efficiency.
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Step 04
Pure Water Collected
Mineral-rich, fluoride-reduced water collects in the lower chamber. No stripping of beneficial minerals. Only contaminants are removed.
Maintenance Made Simple
Know Exactly When to Replace Each Part
The FluoRid media simply
needs a refill every 4 months. That's it.
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Month 0
Install your POSTreat Steel Filter elements. Begin filtering.
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Month 4
Refill the FluoRid media (about 1,060 gallons reached). The steel casing stays.
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Month 8
Second FluoRid media. Everything else stays put
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Month 12
Replace the carbon filter elements (annual) and refill the FluoRid media.
Built to Last. Designed for Annual Replacement
Made with high-quality CTC-60 coconut shell activated carbon, Phoenix Gravity Carbon Filter Elements are designed to last up to 12 months, depending on your source water quality and usage. Enjoy reliable filtration and better-tasting water, with a simple once-a-year replacement routine.
FluoRid Media Refill — Every 4 Months
Only the internal media needs replacing — not the whole filter. Subscribe and we'll track your replacement schedule automatically, shipping your FluoRid refill before you run dry. Subscribers also save 5% per order.
The Science Behind the Filter
Why Fluoride Reduction Matters for Your Family
About 75% of Americans receive fluoridated tap water. While low-level exposure is managed, emerging peer reviewed research has raised important questions about cumulative fluoride intake over years of daily consumption.
Neurological Health
Multiple peer-reviewed studies have identified associations between prolonged high-fluoride water consumption and cognitive effects — particularly in developing children. Reducing daily fluoride intake through filtered water is a meaningful precautionary step many families are taking today.
Neurological Health
Multiple peer-reviewed studies have identified associations between prolonged high-fluoride water consumption and cognitive effects — particularly in developing children. Reducing daily fluoride intake through filtered water is a meaningful precautionary step many families are taking today.
Hormonal Balance
The thyroid regulates your metabolism, energy, and hormonal equilibrium. Research suggests prolonged fluoride exposure may interfere with thyroid activity — especially in people with iodine deficiency — making fluoride-reduced water an increasingly important wellness priority.
Hormonal Balance
The thyroid regulates your metabolism, energy, and hormonal equilibrium. Research suggests prolonged fluoride exposure may interfere with thyroid activity — especially in people with iodine deficiency — making fluoride-reduced water an increasingly important wellness priority.
Bone & Joint Integrity
While fluoride plays a role in dental strength at controlled levels, excess fluoride over time has been linked to skeletal fluorosis — a condition affecting bones and joints with symptoms ranging from stiffness to structural changes. Long-term reduction is your best insurance.
Bone & Joint Integrity
While fluoride plays a role in dental strength at controlled levels, excess fluoride over time has been linked to skeletal fluorosis — a condition affecting bones and joints with symptoms ranging from stiffness to structural changes. Long-term reduction is your best insurance.
Pregnancy & Birth Outcomes
Scientific literature has explored a potential association between elevated fluoride exposure during pregnancy and increased risks of low birth weight and preterm delivery. For expectant mothers, reducing fluoride in drinking water is a straightforward and proactive protective measure.
Pregnancy & Birth Outcomes
Scientific literature has explored a potential association between elevated fluoride exposure during pregnancy and increased risks of low birth weight and preterm delivery. For expectant mothers, reducing fluoride in drinking water is a straightforward and proactive protective measure.
Why Phoenix POSTreat Steel Filter?
The Only Fluoride Filter That Does It All
See exactly how the Phoenix POSTreat Steel Filter Fluoride Reduction Elements stack up against every other option on the market — so you can decide with confidence.
| Feature | Best Value POSTreat Steel Filter | Other Filters |
|---|---|---|
| Removes Fluoride (95%+) | Yes | Partially |
| Preserves Healthy Minerals | Yes | ✗ Strips minerals |
| No Plumbing Required | Yes | Requires installation |
| Stainless Steel (Non-Leaching) | ✓ AISI 304 | ✗ Plastic parts |
| Aluminum-Free Media | Yes | No |
| Upfront Cost | ✓ $99 | ✗ $300–$1,500+ |
| Cost Per Gallon | ✓ $0.10 | ~$0.05 - $0.15 |
| Refillable / Zero-Waste | ✓ Steel casing reusable | ✗ Cartridge disposal |
Free US Shipping on $99+
Customer Reviews
Got questions?
We've Got Answers
Will POSTreat fit my filter system?
POSTreat™ Steel Fluoride Reduction Filter Elements thread onto the stems of Phoenix Gravity Carbon Filter Elements and Black Berkey® elements. They fit the standard 14mm stem.
Your lower chamber also needs about 14mm of space below each carbon element. We haven’t tested elements from other brands. If you use a different element, email hello@phoenixwaterfilters.com with its brand and model before you order, and we’ll tell you whether it fits.
Does POSTreat work with my Berkey® system?
Yes. POSTreat threads onto the stems of Black Berkey® elements, below the upper chamber. It also fits Phoenix Gravity Carbon Filter Elements, which many Berkey® owners now use. Phoenix Gravity Carbon Filter Elements are compatible with Berkey® chambers.
If you use Berkey® PF-2 fluoride elements today, take them off and fit POSTreat in their place.
Berkey®, Black Berkey® and PF-2 are trademarks of their respective owner, referenced for published compatibility only.
I’m buying a new Phoenix Gravity system. How do I add POSTreat?
Add it to your system order. On the Phoenix Gravity Water Filter System page, choose the filter option with POSTreat included. That costs less than buying the POSTreat pair on its own. If you already own a system, buy the pair here.
How many POSTreat elements do I need?
You need one POSTreat element for each carbon element. POSTreat comes as a pair (2 POSTreat elements): 1 pair for a 2-element system and 2 pairs for a 4-element system. To order 2 pairs, change the quantity in your cart. Water from a carbon element without POSTreat skips the fluoride stage.
Will POSTreat fit in my lower chamber?
Each POSTreat element is about 2.7 inches in diameter and 5.3 inches tall, and it hangs below the carbon element inside the lower chamber. It requires 14mm of clearance below each element.
With POSTreat fitted, check system dimensions to ensure proper lower chamber clearance before the water reaches the POSTreat elements.
Can I use POSTreat without a carbon element?
No. POSTreat is an add-on that sits under your carbon element. It needs a carbon element above it and doesn’t replace one.
What’s in the box?
Each pair includes a pair of POSTreat™ stainless steel casings preloaded with FluoRid media inside, lid gaskets and a quick-start card.
If anything is missing or damaged, email hello@phoenixwaterfilters.com with your order number and a photo, and we’ll send a replacement at no charge.
How do I install POSTreat?
You don’t need tools, a plumber or electricity. It takes about 10 minutes:
1. Prime your carbon elements first, following their instructions. Only the carbon elements need priming; POSTreat doesn’t.
2. Each casing comes pre-filled with FluoRid media; ensure the lid is tightly closed with the gasket sitting flat.
3. Fit the primed carbon elements into the upper chamber and tighten their wing nuts by hand.
4. Screw one POSTreat element onto each stem, below the wing nut, by hand until snug. Don’t overtighten. Ensure proper thread alignment during installation.
5. Set the upper chamber on the lower chamber. Check that the POSTreat elements don’t touch the bottom.
6. Fill the upper chamber. Pour out the first approximately four rounds of filtered water. Don’t drink it.
POSTreat is leaking. What should I do?
Unscrew the lid, check that the gasket sits flat in its groove and close the lid fully by hand. If water leaks where POSTreat meets the stem, unscrew it and screw it on again slowly, keeping it straight so the threads catch cleanly.
Water that leaks past the lid skips the FluoRid media, so fix the seal before you rely on fluoride reduction. If it still leaks, email a photo and your order number to hello@phoenixwaterfilters.com.
I see black specks in my water. Is that normal?
In the first approximately four rounds, yes. New FluoRid media contains activated carbon, and harmless processing carbon dust can rinse out at first. Pour that water out and don’t drink it.
If specks are still there after that, email a photo and your order number to hello@phoenixwaterfilters.com or call 1-800-917-0455. We’ll help you sort it out and replace the media if needed.
My water has been flowing more slowly since I added POSTreat. What should I do?
With a full upper chamber, the system filters up to 4.2 gallons an hour without POSTreat, and POSTreat elements filter up to 1,060 gallons total over their lifespan.
If flow stops or drops much lower, trapped air is a common cause. Take off the POSTreat elements, take out the carbon elements and prime them again using cold water only, and fit them back in the upper chamber. Then screw POSTreat back on below the wing nuts and refill. Very hard water, or well water with iron or sediment, can also slow flow over time. Still slow? Call 1-800-917-0455.
Will POSTreat change how my water tastes?
It shouldn’t add any taste. If you notice a new taste or smell after discarding the first approximately four rounds, email hello@phoenixwaterfilters.com with your order number.
My FluoRid media is hard or clumped. Is it damaged?
New media should be loose and granular. If it arrives hard or clumped, or the packaging is torn, don’t use it. Email a photo and your order number to hello@phoenixwaterfilters.com within 30 days of delivery, and we’ll replace it.
Keep spare refills sealed in a cool, dry place.
How much fluoride does POSTreat reduce?
In independent testing, a pair of POSTreat™ elements fitted under Phoenix Gravity Carbon Filter Elements reduced fluoride reliably through 1,060 gallons of use. (mg/L is the same as ppm.) Your results depend on how much fluoride your water starts with. Independent test results are available upon request.
Will my water be fluoride-free?
Not completely. POSTreat reduces fluoride; it doesn’t eliminate every trace. Detailed test results are available upon request.
Does POSTreat reduce anything besides fluoride?
POSTreat is made and tested for fluoride only. We haven’t tested it for anything else, so we make no claims for other substances.
Is POSTreat NSF certified?
No. POSTreat isn’t certified by NSF or any other certification body. Its fluoride results come from independent lab testing. Phoenix Gravity Carbon Filter Elements: EPA Est. No. 103092-IND-1. This number identifies the facility where the product was made. It doesn’t mean EPA approval or endorsement.
Does POSTreat reduce minerals like calcium and magnesium?
POSTreat is designed to target fluoride. Unlike reverse osmosis, it isn’t designed to take out beneficial minerals such as calcium and magnesium.
Is FluoRid aluminum-free?
FluoRid contains no activated alumina (aluminum oxide), the media used in Berkey® PF-2 elements and some other fluoride filters. It’s a blend of activated carbon and proprietary fluoride-reduction media.
Can I use POSTreat with well water?
Yes, if your well water is safe to drink. POSTreat and carbon elements aren’t designed to make unsafe water safe, so have your well tested, including for fluoride.
Our 1,060-gallon rating is based on standard test conditions; higher initial fluoride levels may reduce media capacity sooner. Iron or sediment can also slow flow.
How often do I refill the FluoRid media?
Every 4 months or 1,060 gallons per pair, whichever comes first. Most homes reach 4 months first; you’d need to filter about 9 gallons a day to reach 1,060 gallons sooner. You refill only the media; the steel casings are reused.
You can’t see when the media is used up, so follow this schedule. A fluoride test kit can check your filtered water.
Replace Phoenix Gravity Carbon Filter Elements every 12 months. Replace Fluoride Removal Filter media every 4 months. Phoenix Gravity Carbon Filter Elements: EPA Est. No. 103092-IND-1.
How do I pause, skip or cancel my subscription?
You can skip, change or cancel anytime, with no fees. Tap the account icon at the top of the page, log in and open Subscriptions. You can also call 1-800-917-0455 or email hello@phoenixwaterfilters.com.
To stop your next charge, cancel before your renewal date. If you cancel, future refills are $69 each at the one-time price.
How does the subscription work?
If you choose Subscribe, you pay $94 today for your POSTreat™ pair. Then, every 4 months, we ship a FluoRid refill and charge the card you used $59 plus tax, until you cancel.
We email you prior to each charge. You can cancel, skip or change the date anytime in your account under Subscriptions, or by calling 1-800-917-0455. To stop the next charge, cancel before it renews.
Prefer to buy once? Choose One-Time Purchase for $99.
How much does a refill cost?
FluoRid Refill Media is $69, or $59 with a subscription. One refill does both casings. At one refill every 4 months, that’s about $17.25 a month, or $14.75 with a subscription.
How do I refill the media?
1. Empty the upper chamber and lift it off the lower chamber.
2. Unscrew each POSTreat element from its stem.
3. Open each lid and empty the used media into your household trash.
4. Rinse each casing with cold water.
5. Pour one pouch of FluoRid into each casing, re-priming as needed, then close each lid with the gasket sitting flat.
6. Screw the POSTreat elements back on below the wing nuts and set the upper chamber on the lower chamber. Fill it, then pour out the first approximately four rounds of filtered water.
I was charged for a refill I didn’t expect. What can I do?
Call 1-800-917-0455 or email hello@phoenixwaterfilters.com within 24 hours to cancel and refund an order before it ships.
What happens if refills are out of stock?
If a refill is delayed, we’ll email you the expected ship date before your renewal and charge you when it ships.
Where do you ship, and how long does it take?
We ship to the Lower 48 states, except California and Iowa where POSTreat cannot be shipped.
Orders leave our U.S. warehouse by UPS or USPS and usually arrive within 3–7 business days. Shipping is free on orders of $99 or more.
Why can’t I ship POSTreat to California or Iowa?
POSTreat elements and FluoRid refills can’t be shipped to California or Iowa because of state rules for water treatment products. If you have a subscription to an address in either state, we will cancel it and issue a refund. Questions? Call 1-800-917-0455.
Something in my order is missing or damaged. What do I do?
Email hello@phoenixwaterfilters.com with your order number and photos of the order and packaging. We’ll reply within 24 hours and send a replacement at no charge.
What is your return policy?
To start a return, email hello@phoenixwaterfilters.com within 30 days of purchase to obtain authorization. POSTreat must be undamaged, resalable, and in its original packaging, and the customer pays return shipping unless the return results from our error. Approved refunds are issued within 10 business days after receipt and approval.
The 100-Day Money-Back Guarantee covers only the filter system housing when buying complete Phoenix Gravity systems. It doesn’t cover POSTreat or FluoRid bought on their own.
What does the warranty cover?
POSTreat’s stainless steel casings carry a 10-year limited warranty against defects in materials and workmanship under normal use.
FluoRid media is refilled every 4 months, so it isn’t part of the warranty. Media that arrives damaged or defective is replaced free if you contact support with your order number and photos.
To make a claim, email a photo and your order number to hello@phoenixwaterfilters.com.
Can I talk to a real person?
Yes. Call 1-800-917-0455 or email hello@phoenixwaterfilters.com. We reply within 24 hours.
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