Pentair Structural tank with 40 gallons total volume in a 16" x 33" shell, for RO setups that outrun a standard 3.2 to 4.4 gallon under-sink tank. Verify fitting size with us before ordering: 800-460-5810.
Pentair Structural tank with 40 gallons total volume in a 16" x 33" shell, for RO setups that outrun a standard 3.2 to 4.4 gallon under-sink tank. Verify fitting size with us before ordering: 800-460-5810.
Not sure if your RO system needs a bigger tank, or whether this one fits?Tell Aidan your RO system's make and model and how you use the water, and he will confirm two things before you spend anything: whether the 1/4 inch connection matches your plumbing, and whether a 40 gallon tank is actually the right fix (sometimes a slow faucet is a delivery-line problem, not a storage problem).
Lower than total volume - depends on air precharge and feed pressure (roughly half is typical in residential setups)*
Dimensions
16" diameter x 33" tall
Inner Shell
Polyethylene (water never touches metal)
Exterior
100% seamless fiberglass construction
Air Cell
Removable - serviceable and replaceable
Mounting
Discharges in any position
Factory Precharge
Around 10 psi - verify and adjust to your RO system's spec at install
Connection
1/4" connection for standard residential RO systems - verify fitting size with us before ordering: 800-460-5810
*Every bladder-style RO tank holds less usable water than its total volume because the compressed air charge occupies part of the shell. Anyone quoting the full 40 gallons "at the faucet" is overpromising.
This Tank Is Right For You If...
✓Large family cooking and drinking with RO water all day
✓Coffee or espresso bar - machines draw RO water faster than a membrane makes it
✓Aquarium / reef keeping - big water changes and top-offs on demand
✓Light commercial - restaurants, offices, breakrooms with multiple draw points
✓Multiple RO outlets - kitchen faucet + fridge line + ice maker on one system
...And Wrong For You If
✗ You only fill glasses and a coffee maker - a standard 3.2 to 4.4 gallon under-sink tank is plenty, and this tank is 33 inches of capacity you will not use
✗ You want faster faucet flow from a tank that is already keeping up - flow rate is set by the delivery line and faucet, not tank size
Verify fittings before ordering. The ROmate-40 uses a 1/4" connection compatible with standard residential RO systems, but plumbing details vary by brand and model. Call or text 800-460-5810 with your RO system's make and model and we will confirm fit in two minutes.
When the Tank, Not the Membrane, Is the Bottleneck
40 gallons of Pentair Structural storage for high-demand reverse osmosis
A reverse osmosis membrane makes water slowly, a few dozen gallons over a whole day, which is why every RO system stores finished water in a pressurized tank. The tank, not the membrane, decides how much water you can draw at once. When a coffee bar, a big family kitchen, an aquarium, or a light commercial sink keeps outrunning a standard 3.2 to 4.4 gallon under-sink tank, the fix is not a bigger membrane; it is bigger storage.
The ROmate-40 is Pentair Structural's high-capacity answer: 40 gallons of total volume in a 16 inch by 33 inch shell, with a polyethylene inner shell, a seamless fiberglass exterior, and a removable air cell that can be serviced or replaced instead of scrapping the tank. It discharges in any position, so it fits basements, closets, and back-of-house spaces. Usable drawdown is lower than total volume on every bladder-style tank: it depends on air precharge and feed pressure, and we say so plainly instead of quoting you 40 gallons at the faucet.
It connects to standard residential RO systems with a 1/4 inch connection. Verify the fitting size with us before ordering: call or text 800-460-5810 and we will confirm compatibility with your exact system, 7 days a week.
✔40 Gallons Total Volume
✔Pentair Structural Build
✔Seamless Fiberglass Exterior
✔Removable, Serviceable Air Cell
✔Discharges in Any Position
✔Fits Standard Residential RO (1/4")
✔ Expert RO Storage & Sizing Support
From fitting verification to precharge setup to diagnosing whether your bottleneck is storage, membrane, or plumbing, Aidan provides hands-on support at every step. Real person, real expertise, 30+ years of water treatment experience. No bots, no scripts.
📞 Call Us800-460-5810
✉️ Email Supportsupport@midatlanticwater.net
🕒 Live Hours7 days a week
Frequently Asked Questions
Total volume is 40 gallons, and we want to be straight about what that means: the usable drawdown (what you can actually pour before the tank refills) is lower, because part of the shell holds the compressed air charge that pushes water out. The exact number depends on your air precharge setting and feed pressure; roughly half of total volume is a reasonable expectation in typical residential setups. That is still several times the usable water of a standard 3.2 to 4.4 gallon under-sink tank, which is the entire point. Be skeptical of any seller quoting the full 40 gallons at the faucet.
Almost certainly, if it is a standard residential RO system: the ROmate-40 uses a 1/4 inch connection and replaces or supplements the factory storage tank. But plumbing details vary by brand and model, so verify the fitting size with us before ordering. Call or text 800-460-5810 with your system's make and model and we will confirm fit in two minutes.
People who outrun a standard tank: large families cooking with RO water, coffee and espresso bars, restaurants and breakrooms, aquarium and reef keepers doing big water changes, and homes running multiple RO outlets (faucet plus fridge plus ice maker). If you only fill glasses and a coffee maker, a standard under-sink tank is plenty and we will tell you so. The membrane makes water slowly either way; the tank is what determines how much you can draw at once.
No, and this matters: flow rate at the faucet is set by the delivery line, faucet, and tank pressure, not by tank size. What a bigger tank changes is how LONG you can draw before the pressure tapers and the membrane has to catch up. If your complaint is a slow trickle from a tank that never runs empty, the fix is elsewhere in the system; call us before buying and we will diagnose it honestly.
It is a Pentair Structural tank with a polyethylene inner shell (the water never touches metal), a 100% seamless fiberglass exterior, and a removable air cell that can be serviced or replaced rather than scrapping the whole tank. It discharges in any position, so it can be placed flexibly in basements, closets, and back rooms. The factory air precharge is around 10 psi; verify and adjust it to your RO system's spec at install.
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ROmate-40 Reverse Osmo...$995.00
Why a Pentair Structural Tank Costs More
Serviceable, corrosion-proof storage vs disposable import tanks
What you get with budget import RO tanks
Large budget RO tanks are typically painted steel shells with glued-in bladders: when the bladder fails or the shell rusts, the whole tank is scrap, and a 40 gallon tank failing means 40 gallons on your floor. Listings rarely state the precharge spec, fitting size, or whether the air cell is serviceable, and there is nobody to ask.
Most also overpromise capacity, quoting total volume as if it were water you can pour at the faucet.
The Real Cost Comparison
Budget Import 40 Gal Tank
$400 - $700
❌Lifespan: Fails in 3-4 years
❌Result: Frequent repairs, poor water quality, leaks
❌Support: None
Glued bladder, rust-prone shell, scrap on failure, no support
Best Long-Term Value
Pentair Structural ROmate-40
$995
✅Lifespan: Lasts 15+ years
✅Result: Done right the first time, peace of mind
✅Support: Lifetime USA Support
Serviceable air cell, seamless fiberglass, fit verified by phone
A storage tank is the least glamorous part of an RO setup and the most expensive one to have fail, because it fails as water on your floor. The serviceable air cell means this tank gets repaired, not replaced, and the fiberglass shell never rusts. Over a decade of service, that is the cheaper tank.
What you get with the ROmate-40
A Pentair Structural tank: polyethylene inner shell so water never touches metal, a 100% seamless fiberglass exterior that cannot rust, and a removable air cell that can be serviced or replaced instead of scrapping the tank. It discharges in any position, so placement is flexible.
And the honest sizing conversation comes included: we verify your fitting size and confirm a bigger tank is actually the fix before you spend anything. 800-460-5810, 7 days a week.
Contact Us
800-460-5810
We're here to help.
30-Day Return Policy
30 days from delivery to make sure it's right for your setup
If you're not satisfied with the ROmate-40 storage tank within 30 days of delivery, contact us and we'll arrange the return. You'll get a full refund of the purchase price once it is back in our warehouse. No restocking fees on unopened items, and no runaround.
10,000+Systems Installed
455+Verified Reviews
30+Success Rate
We have been helping homeowners solve water problems for over 30 years, and we would rather confirm fit before you order than process a return after. Call or text 800-460-5810 with your system's make and model and we will verify compatibility in two minutes. If something still is not right, the 30-day window has you covered.
The Industry "Return Policy" Trap
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Many online retailers technically accept returns, but the fine print requires you to pay return shipping and then deducts a 15-25% restocking fee. It is a return policy designed to discourage returns.
Ours is different: contact us within 30 days, we provide return instructions, and unopened items carry no restocking fee.
How Our 30-Day Return Works
1
Contact Us Within 30 Days
Call, text, or email within 30 days of delivery to start the return. We'll ask a few quick questions about the item's condition.
2
We Send Return Instructions
This ships back as an ordinary parcel - no freight logistics. We walk you through repacking it.
Refund Issued, No Restocking Fee
Once the item is back at our warehouse and inspected, we issue a full refund to your original payment method. No restocking fees on unopened items.
Before you order a 40 gallon tank, call or text me your RO system's make and model. I will confirm the 1/4 inch connection matches your plumbing and that bigger storage is actually your bottleneck. If it still is not right, 30 days, no restocking fee on unopened tanks.
