For the Undersink Wellness System and Whole Home drinking tap
Wellness System filters
ToxyGuard + AlkaGuard, city water
Replace 3,000 gallons or 1 year, whichever comes first
Filter detailsSentry H2O filters · auto-ship
Never think about filters again.
Three purpose-built filters keep every Sentry H2O system doing its job. Subscribe once and the exact set for your system arrives on schedule at 10% off. Below: what each filter does, and when to change it.
Filter auto-ship
Never think about filters again
Pick your system's filters once. Subscribe and the exact set arrives on schedule at the auto-ship price, so the water stays as good as the day you installed it.
- Save 10% on every delivery
- Free Ground shipping contiguous US
- Skip or cancel anytime
For the Sentry H2O Portable System
Portable System filters
ToxyGuard + AlkaGuard, for known treated water
Replace 12 months or 3,000 gallons, whichever comes first (per installed filter set)
Filter details
For the Sentry H2O Shower Filter
Shower cartridge
Exact-fit replacement cartridge, designed to reduce chlorine and odor
Replace Approximately 3,000 gallons, or sooner if performance declines
Filter detailsAuto-ship is a Shopify subscription: your first delivery is charged at checkout and ships with your order, then each renewal is charged and shipped on the schedule shown. Shopify shows the full recurring terms at checkout before you pay. Skip or cancel anytime from your account, or call (435) 990-3778. Filter life varies with your water and use; the filter-life estimator gives an estimate for your home.
- 1ToxyGuardtakes the toxins out
- 2AlkaGuardadds the minerals back
- 3BioChemGuardoptional submicron media stage
The three filters
What each one actually does
Stage 1 · the workhorse
ToxyGuard
Catalytic carbon + reduction media
The toxin filter. Water hits ToxyGuard first, where a powerful blend of catalytic-carbon and reduction media adsorbs the chemistry city treatment and old pipes leave behind — a salt-free scale-conditioning process helps control scale, and an oxygenation stage adds oxygen back.
What it handles
- Chlorine & chloramine
- Trihalomethanes (THMs)
- Hydrogen sulfide (odor)
- Lead, arsenic & mercury
- Fluoride
- Sediment to 1 micron
- Scale — salt-free scale conditioning
- Oxygenation — adds oxygen back
Its salt-free scale-conditioning process is designed to change how hardness minerals behave so they are less likely to form scale — no salt, chemicals or regeneration cycle, and not conventional softening (hardness minerals stay in the water) — and it re-oxygenates the water so it tastes alive rather than flat. In the independent under-sink lab test, most PFAS compounds were not detected above the lab's method detection limit after treatment; the three quantified before and after fell 97.44% (PFHxA), 99.29% (PFHpA) and 99.93% (PFBS).
Replace at 3,000 gallons or 1 year, whichever comes first
Stage 2 · the mineralizer
AlkaGuard
Mineral enrichment, not stripping
The good-taste filter. Where reverse osmosis strips water down to almost nothing, AlkaGuard is designed to release magnesium and calcium back into the water and gently raise the pH — neutralizing acidity as it goes. Because it adds minerals, it can raise measured hardness: this is mineral enrichment, not softening.
What it handles
- Adds calcium & magnesium
- Gently raises pH
- Neutralizes acidity
- Mineral enrichment
- Rounder, smoother taste
Lab-tested 6.83 → 8.21 pH on the under-sink system — the minerals reverse osmosis removes are kept in. Its media also carries broad adsorption of VOCs, chloramines and taste-and-odor compounds while it re-mineralizes. A taste-and-mineral difference, not a health claim.
Replace at 3,000 gallons or 1 year, whichever comes first
Optional Stage 3 · wells & extra margin
BioChemGuard
NASA-derived submicron media (Argonide NanoCeram)
The peace-of-mind filter. Added on the TriGuard (well) configuration and the Premium Upgrade portable set, BioChemGuard uses NASA-derived electropositive attraction to trap particles far smaller than its own pores.
What it handles
- Argonide media data; no system certification
- Chlorine & iodine
- >99.99%, 0.2 micron latex-sphere test (Argonide media test, not a system test)
- >3 LRV cysts (Argonide media test, not a system test)
Sentry confirmed in writing in October 2026 that BioChemGuard uses Argonide NanoCeram PAC media. In Argonide’s own media tests, NanoCeram reached >99.99% efficiency at 0.2 micron (latex test spheres), >5 LRV retention of the test bacterium Klebsiella terrigena, >3 LRV cyst retention and >99.95% endotoxin removal; Argonide also lists virus among what the media reduces or removes. These are Argonide’s own media tests of NanoCeram and NanoCeram PAC, not a test or certification of the finished Sentry system. If your water is microbiologically unsafe or of unknown quality, disinfect it before or after the filter.
Replace at 3,000 gallons or 1 year, whichever comes first
And for wells — a formula built from your test
WellGuard
Well-treatment formula tailored to your water test · whole-home well tank
The three filters above are the under-sink drinking cartridges. Well water differs from one address to the next, so the whole-home well systemdoes not use one fixed recipe. WellGuard is Sentry H2O's well-treatment formula: the tank media and blend are selected from your lab water test to address what it finds — such as iron, manganese, arsenic, sulfur or nitrates — and the configuration is confirmed before shipment. It is not a fourth cartridge added to the under-sink set.
What a formula can target, based on your test
- Iron & manganese
- Nitrates (selective ion-trapping)
- Arsenic
- Radium & uranium
- Hydrogen sulfide (rotten-egg odor)
- Heavy metals — zinc, copper, lead
- Sediment & turbidity to 3 microns
Which set is mine?
Your water decides the set
The under-sink Wellness System ships in two configurations. Same housing — the filters inside are the difference.
DualGuard
City waterToxyGuard + AlkaGuard
Two filters for municipal, chlorinated supply — takes the chlorine, chloramine, PFAS, lead and arsenic out, then adds minerals back for great-tasting water.
Shop the Wellness SystemTriGuard
Well & extra marginToxyGuard + AlkaGuard + BioChemGuard
Adds the third BioChemGuard stage, Argonide NanoCeram PAC media (Argonide media data, not a test of the finished system) — the right choice for wells, homes near farmland, or after flooding. What BioChemGuard does
Choose TriGuardWhole-home systems treat every tap and are configured differently — including nitrate-selective media selected from independently obtained well results where nitrates are a concern. See whole home →
Keeping it fresh
When to replace each filter
Under-sink drinking filters
3,000 gallons or 1 year
Whichever comes first, for DualGuard and TriGuard sets. Subscribe and the set arrives every 12 months at 10% off, or buy a one-time set.
Subscribe & saveWhole-home tank media
City: every 1–3 years
For city systems, refresh with the Whole Home Revitalizer every 3 years for one person, every 2 years for 2–3 people, and yearly for 4+. Whole-house well maintenance is confirmed after testing and configuration.
See the RevitalizerPortable filter sets
About a year
Standard (city) or Premium Upgrade BioChemGuard (well / off-grid) sets swap yearly. Subscribe so you're never caught without on the road.
Subscribe & saveFilter life varies with your water quality and how much you use. A filter-life estimate for your home is on the filter-life estimator.
Beyond your glass
Every filtered glass is a bottle that never gets made.
~0
single-use bottles a family of four can skip every year with filtered water on tap.
9%
of all plastic ever made has been recycled
OECD, 2022
~80%
still sits in a landfill or the environment
Science Advances, 2017
1M
plastic bottles bought every minute, worldwide
Euromonitor / The Guardian
Bottle count estimated from ~156–167 bottles per person a year (industry compilations) — yours depends on what you buy today. Plastic figures describe global plastic waste broadly; sources on file.
Straight answers
Filter questions
How often do the drinking filters need changing?+
Replace the under-sink drinking filters — ToxyGuard, AlkaGuard and (on TriGuard) BioChemGuard — at 3,000 gallons or 1 year, whichever comes first. Subscribe to filter auto-ship at the top of this page and the exact set arrives every 12 months at 10% off.
How does filter auto-ship work?+
Auto-ship is a Shopify subscription. Your first set is charged at checkout and ships with your order; after that, the same set is charged and shipped every 12 months at 10% off the one-time price, with free Ground shipping in the contiguous US. Shopify shows the full recurring terms at checkout before you pay. Skip or cancel anytime from your account, or call (435) 990-3778.
What is the difference between DualGuard and TriGuard?+
DualGuard is the 2-filter set for city water: ToxyGuard + AlkaGuard. TriGuard adds a third BioChemGuard stage, Argonide NanoCeram PAC media (Sentry confirmed in writing), whose own media tests show >99.99% efficiency at 0.2 micron (latex test spheres); that is not a test or certification of the finished Sentry system. It is a good fit for wells, homes near farmland, or anyone who wants the extra margin.
Do these filters waste water like reverse osmosis?+
No. There is no drain line and no wastewater. A typical reverse-osmosis system sends five gallons or more down the drain for every gallon it makes; the Sentry H2O stages send none — and AlkaGuard keeps the minerals RO strips out.
What about nitrates?+
For well-water nitrate concerns, a whole-home well system can use nitrate-selective media selected from your lab results — targeted reduction without stripping minerals the way reverse osmosis does.
Are these tested by a lab?+
Yes, as water samples. The independent before-and-after lab reports on our Science page are third-party tests of water samples, not a certification. We do not call the complete systems NSF certified; Sentry H2O uses tested or certified components where applicable.
Real customers, real water
Rated by Sentry H2O customers
Verified Sentry H2O reviews — the same filters, in real kitchens.
Sentry H2O store review snapshot, independently collected by Judge.me, as of August 2026.
4.92/5★★★★★
Based on 531 reviews as of August 202692% Verified
August 2026 review-count snapshot.
Rating, count and verification rate checked on Judge.me September 15, 2026.
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Backed by 531 Sentry H2O store reviews · 4.92/5. Educational guidance only — not health or medical advice.