Rubber is Inside Your Reverse Osmosis Tank? (I Cut It Open…)
What’s REALLY Inside Your Reverse Osmosis Tank? (I Cut One Open to Find Out)
Most people install a reverse osmosis (RO) system assuming they’re getting the cleanest water possible.
I thought the same thing.
Until I cut one open.
🎥 The Experiment
A patient had mentioned something interesting to me:
“You know there’s a rubber membrane inside those tanks, right?”
So naturally… I grabbed a saw and decided to find out.
After about two years of use, we opened up a standard RO storage tank.
At first glance, everything looked normal:
Solid metal exterior
But then we got deeper into it…
😳 What We Found
Inside the tank was exactly what I was told:
👉 A rubber bladder (balloon-like membrane) lining part of the interior
This bladder:
Expands as water fills the tank
Provides pressure to push water out when you open the faucet
In other words:
Your “clean” RO water is sitting inside a rubber container.
And when you actually touch it…
It feels:
Slippery
Slightly slimy
Not exactly something you’d expect your drinking water to be stored in
🧪 What Is That Rubber?
Most RO tanks use butyl rubber, which is:
Food-grade
Low permeability (doesn’t let much pass through)
Commonly used in water systems
That sounds reassuring—but it doesn’t mean zero interaction with your water.
⚠️ Does Rubber Leach Into the Water?
This is where things get important.
Short answer:
👉 Yes—at very low levels
Especially:
When the tank is new
When water sits in the tank for long periods (stagnation)
What can potentially leach:
Trace volatile organic compounds (VOCs)
Minor residues from manufacturing
Very small amounts of rubber-related compounds
Now to be clear:
👉 Most systems meet safety standards (NSF/ANSI)
👉 Levels are considered “safe” by regulatory guidelines
But…
🧠 The Functional Medicine Perspective
Here’s where I look at it differently.
It’s not just:
“Is this toxic at high levels?”
It’s:
“What is the cumulative effect of low-level exposure over time?”
Because this isn’t your only exposure.
You’re also getting:
Plastics in food packaging
Environmental toxins
Personal care chemicals
Air pollutants
So even if the RO tank contributes a small amount, it adds to your total toxic load.
⚕️ Potential Health Considerations
There’s no strong evidence that RO tank rubber causes disease directly.
But from a root-cause perspective, possible concerns include:
Chemical sensitivity in susceptible individuals
Contribution to overall inflammatory/toxic burden
Again—this is about accumulation, not a single exposure.
🚱 The Bigger Problem: Stagnant Water
What concerned me just as much as the rubber…
👉 Water sitting in that tank for hours (or days)
That can lead to:
Biofilm development
Bacterial growth
More interaction with the bladder material
So now you’ve got:
Rubber contact
Stagnation
Time for leaching to occur
🧼 Can You Clean the Inside?
Unfortunately:
👉 You cannot clean the inside of the rubber bladder
It’s sealed and inaccessible.
What you can do:
Flush the system regularly
Sanitize the system 1–2x per year
Replace the tank every 5–7 years
But none of that removes the rubber itself.
💡 So… Is There a Better Option?
After cutting this open, I started asking:
“Why are we storing purified water in rubber at all?”
Better alternatives:
1. Tankless RO systems - Stay tuned for a follow up review on this
No storage tank
No rubber bladder
Water is filtered on demand
Less stagnation
👉 This is the simplest upgrade
2. Stainless steel storage + float valve (advanced setup)
RO fills a stainless tank
Float valve shuts off flow when full
No rubber contact
Downside:
Requires pump or gravity feed
More complex setup
3. Hybrid approach - This is the best approach if you currently have a tank RO system and aren’t ready to spend the money on a new system.
RO filtration
Glass or stainless storage
Remineralization
🤔 What About Berkey Filters?
I mentioned going “back to Berkey” in the video—but there’s a catch.
They’re:
Not available in California
Surrounded by regulatory and certification issues
That doesn’t automatically make them bad…
…but it does raise questions worth looking into.
🧩 Final Thoughts
Cutting open that tank changed how I think about RO systems.
Here’s the reality:
RO filtration itself is excellent
But the storage method matters
👉 You’re removing contaminants…
👉 Then storing the water in rubber…
👉 Letting it sit…
That’s not ideal.
👊 My Takeaway
If you’re using RO:
Don’t panic—this isn’t a major toxin exposure, but toxins do accumulate over time.
But do optimize where you can
Best move:
👉 Switch to tankless RO
Next best:
👉 Replace old tanks + flush regularly
