BioGuard Stabilizer 100 | Chlorine Stabilizer

SKU: 23481BIO
$43.99

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Description

BioGuard Stabilizer 100 is 100% cyanuric acid — sunscreen for your chlorine. It's a fully soluble granular product that prevents free chlorine from being destroyed by sunlight, and on an outdoor pool it's the difference between chlorine that lasts and chlorine that's gone by dinnertime.

Ultraviolet light is the single largest drain on chlorine in an outdoor pool. Unprotected free chlorine breaks down rapidly in direct sun — a pool with no stabilizer can lose a substantial share of its residual in a matter of hours on a bright summer day. That's chlorine you paid for, doing nothing but absorbing UV. The pool then reads low, the owner adds more, and the cycle repeats every afternoon.

Cyanuric acid stops that. It bonds loosely with free chlorine and shields it from ultraviolet degradation, then releases it as the chlorine is consumed doing actual work. The residual survives the day, and chlorine consumption and maintenance costs both drop measurably. It also improves the efficiency of chlorine generators, which is why salt pool owners care about it as much as tablet users do.

The catch, and it's an important one: cyanuric acid accumulates permanently. It doesn't evaporate, doesn't break down, doesn't burn off, and doesn't filter out. Every dose stays until you dilute it. And if you feed chlorine with trichlor tablets, dichlor granules, or a dichlor-based shock, you're already adding stabilizer with every application — those products are built on a cyanurate backbone.

That makes this a product to buy deliberately, based on a test reading, rather than as routine maintenance. Get it right and your chlorine stretches much further. Overshoot and you create the opposite problem: a pool that tests fine and behaves like it has no sanitizer at all.

Pro Tip: Test cyanuric acid before you buy this, and don't add it at all if you feed with trichlor or dichlor. Tablets, sticks, granular dichlor sanitizer, and dichlor-based shock all contribute cyanuric acid every time you use them — a pool on tablets typically reaches its target stabilizer level on its own within weeks and keeps climbing from there. Adding Stabilizer 100 on top of that is how pools end up locked up in August. This product is for pools starting from a fresh fill, pools using unstabilized chlorine like cal hypo or liquid, and salt generator pools. If you're on tablets, test first and you'll likely find you need none.

Brand

BioGuard®

What's in the Box
  • 1 x BioGuard Stabilizer 100, 5 lb container
  • Full manufacturer label with dosing rates and application directions

At 1 lb per 3,000 gallons for a 40 ppm level, a 5 lb container treats a 15,000-gallon pool to 40 ppm, or a 20,000-gallon pool to 30 ppm.

Key Features

Prevents Chlorine Loss Due to Sunlight

Shields free chlorine from ultraviolet degradation, the largest single source of chlorine loss in an outdoor pool during summer.

Reduces Chlorine Consumption and Maintenance Costs

Chlorine that survives the afternoon is chlorine you don't have to replace. Proper stabilizer levels cut both how much sanitizer a pool uses and how often you're out there adding it.

Improves Efficiency of Chlorine Generators

Salt pools benefit directly — a protected residual means the cell doesn't have to run as hard or as long to hold the same chlorine level, which also extends cell life.

100% Cyanuric Acid

No fillers and no additional chemistry. The entire contents is the active ingredient.

Totally Soluble Granular Formula

Dissolves completely with no residue left behind, though it takes time in the water — see the application directions for why that matters.

Simple, Predictable Dosing

1 lb per 3,000 gallons establishes 40 ppm; 1 lb per 4,000 gallons establishes 30 ppm. Straightforward to calculate for any pool size.

Can Be Added Through the Skimmer on Plastic Piping

Pools with plastic plumbing have a second application option, which is useful when broadcasting isn't practical.

How It Works

The product is 100% cyanuric acid, and its function is genuinely different from anything else in a pool routine. It doesn't sanitize, oxidize, balance, or clarify. Its only job is to protect chlorine from the sun.

Free chlorine in water exists largely as hypochlorous acid, and hypochlorous acid is readily broken apart by ultraviolet light. In direct summer sun, an unstabilized pool can lose a large fraction of its free chlorine within hours. The chlorine isn't being consumed by bacteria or organic waste — it's simply being destroyed by sunlight before it can do any work.

Cyanuric acid forms a weak, reversible bond with free chlorine. Bonded chlorine is shielded from UV, so it survives in the water. As unbonded chlorine gets consumed sanitizing the pool, the bond releases more chlorine back into active service. The result is a reservoir that's protected from the sun but still available for work — which is exactly what you want.

The tradeoff is at the heart of every stabilizer decision. Bonded chlorine is less immediately reactive than free chlorine. At correct levels that hardly matters, because plenty of chlorine remains available. But as cyanuric acid climbs, a progressively larger share of your chlorine is tied up at any moment, and sanitizing power drops even though your test kit reports the same number. This is called chlorine lock, and it's why a pool can read a textbook 3 ppm and still go cloudy or grow algae.

What makes this consequential is permanence. Cyanuric acid doesn't evaporate, doesn't degrade in sunlight, isn't consumed by chlorine, and passes straight through any filter. The level only rises — from this product, and from every trichlor tablet, dichlor granule, and dichlor-based shock you add. The only way to lower it is dilution: partial drain and refill.

That's why the target range matters more here than on almost any other product. Enough stabilizer to protect the residual, not so much that it locks the chlorine up.

Pro Tip: If your pool "stopped holding chlorine" in late summer, test cyanuric acid before buying more shock. This is the most common misdiagnosis in pool care. A pool fed by trichlor tablets all season accumulates stabilizer steadily, and once it climbs well past the target range, free chlorine becomes progressively less effective at the same test reading. The pool looks properly chlorinated on a strip and behaves like it isn't — cloudy water, algae taking hold, sanitizer that seems to vanish. Adding more chlorine doesn't fix it, because the chlorine isn't missing; it's tied up. A partial drain and refill is the only real correction, and it's cheaper than a month of shocking a pool that can't respond.

Directions for Use

Dosage Reference

  • 1 lb per 3,000 gallons provides an initial stabilizer level of 40 ppm
  • 1 lb per 4,000 gallons provides an initial stabilizer level of 30 ppm

Target Range

  • 30–50 ppm for most chlorinated pools
  • Salt chlorine generator pools may target higher — follow your generator manufacturer's specification
  • Effectiveness declines noticeably as levels climb well above the target range

Always confirm the target on your current product label and against your equipment manufacturer's guidance.

Before You Start

  1. Test cyanuric acid first. Only add what's needed to reach your target from your current reading.
  2. Confirm your pool's actual gallon capacity.
  3. Confirm the pump and filter are running and the filter is clean.
  4. Note your normal operating filter pressure, since it will rise temporarily.

Application

  1. Broadcast directly into the pool, scattering over the surface of the water.
  2. For pools with plastic piping, the product may instead be added slowly through the skimmer.
  3. Keep the water circulating continuously for 24 hours after addition.
  4. When the product reaches the filter there may be a temporary increase in filter pressure, which will dissipate as the product dissolves.
  5. Do not backwash for 48 hours after application.
  6. Retest cyanuric acid several days later to confirm the level. Stabilizer dissolves slowly, so an early test will read low.

Why the Timing Matters

Cyanuric acid dissolves considerably more slowly than most pool chemicals. Much of a fresh dose sits in the filter as it gradually goes into solution, which is exactly why the label calls for 24 hours of continuous circulation and no backwashing for 48 hours. Backwash too early and you flush undissolved product to waste — you've paid for stabilizer that never reached your pool, and your test will read low afterward. It's also why you should wait several days before retesting rather than dosing again based on an early reading.

Storage and Handling

  • Store in a cool, dry, well-ventilated area away from moisture
  • Keep the container tightly closed and clearly labeled
  • Store separately from sanitizers, acids, and oxidizers
  • Keep out of reach of children and pets
  • Avoid breathing dust; broadcast downwind of yourself on a breezy day
  • Read and follow all label precautions, first aid, and disposal directions before use

Pro Tip: Don't dose twice based on an early test. Cyanuric acid takes days to fully dissolve and register, so a stabilizer test run 24 or 48 hours after application will read lower than where you'll actually land. The classic mistake is testing too soon, seeing a number below target, adding a second dose, and then discovering a week later that you've overshot badly — at which point the only fix is draining and refilling. Add the calculated amount once, give it a full week, then test. Patience costs nothing here; impatience costs a water bill and a season of underperforming chlorine.

Specifications
  • Brand: BioGuard
  • Product Type: Chlorine stabilizer / conditioner
  • Form: Totally soluble granular
  • Net Weight: 5 lb
  • Manufacturer Part Number: 23481BIO
  • Active Ingredient: Cyanuric acid, 100%
  • Function: Protects free chlorine from ultraviolet degradation
  • Dose for 40 ppm: 1 lb per 3,000 gallons
  • Dose for 30 ppm: 1 lb per 4,000 gallons
  • Target Range: 30–50 ppm for most chlorinated pools
  • Application Method: Broadcast over the water surface, or add slowly through the skimmer on pools with plastic piping
  • Circulation After Application: 24 hours continuous
  • Backwash Restriction: Do not backwash for 48 hours after application
  • Expected Filter Pressure: Temporary increase that dissipates as the product dissolves
  • Reversibility: Cyanuric acid can only be lowered by draining and refilling
  • Intended For: Outdoor, chlorinated pools only
  • Not For Use In: Indoor pools, bromine pools, biguanide pools, spas, or hot tubs
  • Suitable Surfaces: Plaster, gunite, vinyl liner, fiberglass, painted
  • Filter Compatibility: Sand, cartridge, and DE
  • Shipping Classification: DOT-regulated — ground shipping only
Compatibility

Intended Use

  • Outdoor, chlorinated pools only. This is the manufacturer's stated scope.
  • In-ground and above-ground pools
  • Plaster, gunite, vinyl liner, fiberglass, and painted surfaces
  • Sand, cartridge, and DE filtration

When You Need It

  • New fill or fresh start-up, where stabilizer is at zero
  • Pools using unstabilized chlorine — calcium hypochlorite shock, liquid chlorine, or bleach — which add no cyanuric acid of their own
  • Salt chlorine generator pools, which produce unstabilized chlorine and need stabilizer to hold it
  • After a significant partial drain and refill, which dilutes stabilizer along with everything else

When You Probably Don't

  • Pools fed by trichlor tablets or sticks — these add cyanuric acid continuously and usually reach target on their own
  • Pools using granular dichlor sanitizer or dichlor-based shock — same reason
  • Any pool whose stabilizer test already reads at or above the target range

Where It Does Not Apply

  • Indoor pools — no sunlight, so there's nothing to protect against and the stabilizer only reduces chlorine effectiveness
  • Bromine pools — cyanuric acid does not protect bromine, and stabilizer should not be added to a bromine-treated pool
  • Biguanide pools — no chlorine present, so there's nothing to stabilize
  • Spas and hot tubs — typically covered and rarely in direct sun; follow your spa manufacturer's guidance instead

Products That Also Add Cyanuric Acid

  • Trichlor tablets and sticks — stabilized; add cyanuric acid with every application
  • Granular dichlor sanitizer — stabilized
  • Dichlor-based shock — stabilized
  • Calcium hypochlorite shock — unstabilized; adds none
  • Non-chlorine oxidizer — adds none

Important Handling Cautions

  • Do not backwash for 48 hours after application. Backwashing early flushes out product that hasn't dissolved yet.
  • Never mix with other chemicals. Add products separately with circulation between additions.
  • Do not overshoot. Cyanuric acid can only be reduced by draining and refilling.
  • Expect a temporary filter pressure increase as the product passes through — this is normal and dissipates as it dissolves.

Most products purchased from our online shop within the last 30 days are eligible for return. Please review our return policy to see the list of items that cannot be returned.

Some major items that are non-returnable:

  • Gift cards
  • Electronics
  • Pumps / Motors
  • Hot Tubs
  • Closeouts
  • Fireplaces
  • Electric Fireplaces
  • Massage Chairs
  • See return policy below for full list of non-returnables.

BioGuard® Brand FAQs

What is the BioGuard 3-Step Care System?

It's the brand's core program for traditional chlorine pools, and it reduces routine care to three jobs.Step 1, sanitize— SilkGuard Complete® tabs or sticks maintain a continuous chlorine residual that kills bacteria and controls algae between applications.Step 2, shock— Smart Shock® is applied weekly to oxidize the organic waste bathers leave behind, break apart chloramines, and restore clarity.Step 3, prevent— Algae Complete® stops algae before it establishes rather than fighting it after it blooms. The system works in pools of any size and surface type that circulate 10 to 24 hours per day.

What's the difference between BioGuard and SpaGuard?

They're sister brands from the same water-care company.BioGuard is the swimming pool line. SpaGuard is the spa and hot tub line.The split isn't marketing — pool dosing is calculated for tens of thousands of gallons at ambient temperature, while spa dosing is calculated for a few hundred gallons at 100°F. Pool packaging makes accurate spa measurement nearly impossible, and a pool-sized dose in a hot tub is a serious overdose. Match the product line to the vessel.

Which BioGuard program is right for my pool?

Equipment usually decides it. Pools running a standard chlorinator, feeder, or skimmer application belong on the3-Step Care System. Pools with a salt chlorine generator should be on thesalt pool programs— Mineral Springs® or SaltScapes® — which are formulated around the specific scale, balance, and cell-care demands of a generator. Owners who want no chlorine or bromine in the water at all use BioGuard'snon-chlorine biguanide program, which is a fully separate chemistry with its own sanitizer, oxidizer, and algaecide.

Can I mix BioGuard products with chemicals from other brands?

Basic balancers are chemically generic and generally interchangeable — alkalinity increaser is sodium bicarbonate no matter whose label is on the bucket. The real risk sits withsanitizer programs and specialty additives. Never introduce chlorine or bromine into a biguanide pool; the two chemistries destroy each other and produce cloudy water, gummy filter fouling, and a collapsed sanitizer residual. Also avoid stacking algaecides and clarifiers from different brands, since overlapping actives can cause foaming or staining. And regardless of brand, never combine two products in the same bucket, scoop, or feeder — always add them separately with circulation running between.

What is SilkGuard Technology?

SilkGuard® is a conditioning technology built into BioGuard's chlorinating tabs and sticks. It softens the feel of the water against skin and helps protect pool surfaces and equipment from scale formation, so the sanitizer is doing two jobs at once. SilkGuard Complete® products also carrySunShield® Technology, which shields free chlorine from ultraviolet breakdown. UV loss is the largest single drain on chlorine in an outdoor pool during summer, so protecting the residual directly reduces how much sanitizer you consume over a season.

Do BioGuard products work with salt chlorine generators?

Yes. A salt pool is still a chlorine pool — the generator simply produces the chlorine on site instead of you adding it from a bucket. Salt pools still need balancing, weekly oxidation, algae prevention, and scale protection, and they have one extra demand a standard pool doesn't: the generator cell itself accumulates scale and needs periodic cleaning. BioGuard's salt-specific programs are built around exactly those requirements.Do not skip testing on a salt pool— the automation controls chlorine production, not water balance.

About BioGuard®

BioGuard is a professional swimming pool care line built on a simple premise: pool chemicals work better as a program than as a shelf of unrelated purchases. Most water problems homeowners fight through the summer aren't caused by a bad product. They're caused by good products working against each other, applied out of sequence, in water whose balance was never corrected in the first place. BioGuard's entire approach is organized around fixing that — matched products, a defined order of operations, and a diagnostic process behind the recommendation.

The brand sits under the KIK Consumer Products umbrella alongside its spa counterpart, SpaGuard, and it covers the full range of pool water care: sanitizers, shocks, algaecides, balancers, water enhancers, surface cleaners and problem solvers, salt pool products, and off-season closing chemistry.

Three Programs, One Philosophy

  • Traditional Chlorine — the 3-Step Care System — Sanitize, shock, prevent. SilkGuard Complete® tabs and sticks handle daily sanitation, Smart Shock® handles weekly oxidation and clarity, and Algae Complete® handles algae prevention. Suitable for pools of any size and surface type running 10 to 24 hours of circulation per day.
  • Salt Pools — Purpose-built chemistry for pools with a chlorine generator, including the Mineral Springs® and SaltScapes® programs. Salt pools still generate chlorine, and they still need balancing, scale protection, and cell care — these products are formulated for that specific equipment set.
  • Non-Chlorine Pools — A complete biguanide-based program for owners who want no chlorine and no bromine in the water at all, with its own dedicated sanitizer, oxidizer, and algaecide.

Formulation Technologies

Two proprietary technologies show up across the chlorine line and explain a lot of the brand's reputation. SilkGuard® Technology conditions the water so it feels noticeably softer against skin while also helping protect pool surfaces and equipment from scale. SunShield® Technology protects free chlorine from ultraviolet breakdown, which is the single largest source of chlorine loss in an outdoor pool during summer — sanitizer that survives the afternoon is sanitizer you don't have to replace.

Diagnosis, Not Guesswork

BioGuard is sold through trained specialty dealers rather than mass-market channels, and the brand backs that network with the ALEX® water analysis system. ALEX reads a full water sample — sanitizer, pH, total alkalinity, calcium hardness, cyanuric acid, metals, and more — and returns a sequenced correction plan rather than a generic product suggestion. That distinction matters more than it sounds. Cloudy water has at least six common causes, and the fix for a filtration problem is nothing like the fix for a high-pH problem or a phosphate problem. Testing tells you which one you actually have.