ProTuff Team
April 28, 2026 · Pool Chemistry
If your pool water has turned cloudy despite perfect numbers, or pink slime keeps coming back no matter what you do, your biguanide (Baquacil) system may have reached the end of its road.
Switching from biguanide to chlorine — or converting all the way to saltwater — is one of the most misunderstood pool maintenance procedures. Done right, it costs a few hundred dollars and a few days of attention. Done wrong, it can destroy your filter media, turn your water into a murky chemical soup, and leave you staring at a $10,000 repair bill. This guide walks you through every step, by brand and by filter type, so you get it right the first time.
In This Guide
- What Is Biguanide — and Why Owners Switch
- Before You Begin: Prerequisites and Supplies
- The Burn-Out Process: Step by Step
- Filter Management During Conversion
- Brand-Specific Equipment Instructions
- Converting to Saltwater: The Extra Steps
- Common Mistakes and What They Cost
- Safety Rules You Cannot Break
- After the Conversion: Balancing Your New System
- Frequently Asked Questions
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What Is Biguanide — and Why Pool Owners Switch
Biguanide sanitizers — sold under brand names like Baquacil and SoftSwim — use polyhexamethylene biguanide (PHMB) as the active ingredient. Unlike chlorine, PHMB is a polymer-based bactericide that works by disrupting bacterial cell membranes. It does not oxidize contaminants, which means it needs a separate hydrogen peroxide-based oxidizer to function properly.
For the first season or two, a biguanide pool can be crystal-clear and comfortable. But over time, PHMB builds up in the water and in your filter media, creating a sticky gray residue called “Baqua-goo.” Once this happens, the problems compound: cloudy water that won’t clear, repeated outbreaks of pink slime or white water mold, and a maintenance cost that keeps climbing every season.
At that point, most pool owners face a choice: spend another $100+ per month on stronger biguanide products and a drain-and-refill every few years, or make a one-time switch to chlorine or saltwater. The math almost always favors the switch.
Key Fact
Biguanide is chemically incompatible with chlorine. Mixing them without proper “burn-out” creates insoluble waste and makes the water unsafe for swimming.
Before You Begin: Prerequisites and Supplies
Timing matters. The single best time to make this switch is in the spring when you open the pool. Over the winter, biguanide levels naturally drop to their seasonal low — meaning the “burn-out” phase will be faster and cheaper than starting mid-summer when biguanide concentrations are at their peak.
Gather everything before you start. You cannot pause mid-conversion and run to the store — the biguanide breakdown is active, your filter is under stress, and the process needs consistent attention from day one.
⚠ Gather These Supplies Before Starting
- Liquid chlorine or bleach — you will need a large quantity; the biguanide will consume it rapidly at first
- Quality test kit — must measure Free Chlorine (FC) and Combined Chlorine (CC); Taylor K-2006 is the gold standard
- Sequestering agent (e.g., Super Stain Away) — 16 oz per 10,000 gallons to prevent metal precipitation during pH swings
- Replacement filter media — new sand, cartridges, or DE grids; plan to replace after conversion completes
- Cyanuric acid (CYA) — to add once conversion is finished; target 30–50 ppm for a chlorine pool
- Pool brush (stiff bristle), garden hose with spray nozzle
- 3/4″ socket wrench (for Hayward SwimClear clamp bands)
- Safety PPE: chemical-resistant gloves, safety goggles, N-95 mask
Before adding any chemicals, test your water and record the baseline. Know your current pH, alkalinity, calcium hardness, and heavy metals. Adjusting pH and alkalinity during the conversion can precipitate metals out of solution — the sequestering agent keeps them locked in and prevents staining.
The Burn-Out Process: Step by Step
The conversion works by overwhelming the biguanide with high-dose chlorine. The chlorine oxidizes and breaks apart the long-chain biguanide polymers, which then precipitate as a sludge you vacuum out. The sequence below is not optional — each step builds on the last, and skipping or reordering them will cost you time and money.
Add the Sequestering Agent First
Add 16 oz of Super Stain Away per 10,000 gallons of water before touching the pH. This keeps any metals — iron, copper, manganese — locked in solution as you adjust chemistry. Skipping this step can cause permanent metal staining on your plaster or vinyl.
Test and Adjust pH to 7.2–7.4
Adding chlorine to a high-pH biguanide pool causes severe water discoloration and mineral precipitation. Get your pH between 7.2 and 7.4 before adding any chlorine. Use pH decreaser (sodium bisulfate) or muriatic acid — always add acid to water, never water to acid.
Set Your Valve to Recirculate (Sand/DE Filters)
If you have a multiport valve (VariFlo™ on Hayward, similar on other brands), set it to RECIRCULATE before adding the initial chlorine dose. This bypasses the filter media, preventing it from immediately clogging with the Baqua-goo before you’ve started. Cartridge filter owners: leave the filter running normally but plan to clean cartridges frequently.
Raise Free Chlorine to 15 ppm
Add enough liquid chlorine (or bleach) to bring your Free Chlorine (FC) level to 15 ppm. Use a pool calculator like PoolMath to find the exact amount for your pool volume. For a typical 15,000-gallon pool, expect to use 2–3 gallons of liquid chlorine for the initial dose. The water may turn white, cloudy, or clear green — this is normal and expected.
💡 Pro Tip: Shock After Dark
UV degrades unstabilized chlorine at roughly 1 ppm per hour in full sun. At 15 ppm target, a midday dose can lose 40–50% of its effectiveness before evening. Add your chlorine at dusk or after dark to maximize contact time with the biguanide.
Test Hourly and Re-Dose — Run Filter 24/7
In the early stages, the biguanide will consume chlorine rapidly. Test your FC as often as every hour and re-add liquid chlorine whenever FC drops below 15 ppm. Run your filter around the clock. Brush the walls and floor of the pool several times per day to break up and suspend biguanide residuals. This process typically takes 3–7 days, sometimes longer for pools with heavy biguanide loads.
Vacuum Waste Directly to Waste
As biguanide polymers break down, heavy gray sludge (“Baqua-goo”) settles on the pool floor. Switch your valve to the WASTE position and vacuum this directly to waste — do not run it through the filter. Keep a garden hose running to maintain water level as you vacuum.
Confirm the Endpoint — Then Replace Filter Media
The conversion is complete when you lose 1 ppm or less of FC overnight AND your Combined Chlorine (CC) stays at 0.5 ppm or below for two consecutive days. Once those benchmarks are met, immediately replace or deeply strip your filter media (see Filter Management section below). Then add CYA to reach 30–50 ppm before reducing your FC maintenance target.
Filter Management During and After Conversion
Your filter works harder during this process than at any other point in its life. Baquacil creates a sticky gray film on filter media that standard backwashing cannot fully remove. If you skip the media replacement step, that residual will react with your new chlorine and create permanent cloudiness — essentially, you’ll be fighting the conversion even after it’s “done.”
Here’s what to do for each filter type:
Sand Filters
Each grain of silica sand has microscopic rough edges that trap contaminants — and biguanide film. No filter cleaner can reach every grain. Remove and replace the sand entirely after conversion. Scooping out the old sand and pouring in fresh #20 silica sand (for Jandy JS filters) takes 1–2 hours and eliminates any risk of residual reactivity.
During conversion: backwash when pressure rises 8–10 PSI above baseline; switch valve to RECIRCULATE during initial chlorine doses; vacuum to WASTE.
Cartridge Filters
A simple rinse won’t cut it. You must either replace the cartridges entirely (recommended) or perform an overnight soak in a biguanide-specific filter cleaner. If soaking: use a commercial filter cleaner according to package directions — typically overnight. Never use TSP (Trisodium Phosphate) before stripping the biguanide film; it reacts to form a permanent gum-like substance that makes the cartridge unrecoverable.
During conversion: clean cartridges whenever pressure rises 7–10 PSI above clean baseline. Expect to clean them multiple times per day in the early stages.
DE (Diatomaceous Earth) Filters
After conversion: disassemble the tank completely, remove the grid assembly, and soak the grids overnight in a cleaning solution. Clean the tank interior thoroughly to remove all DE powder from every surface. Reassemble with fresh DE powder. Leaving even small amounts of biguanide-contaminated DE will cause problems with your new chlorine system.
During conversion: backwash for 3–5 minutes when pressure rises 8–10 PSI above baseline. For DE filters with a “bump” feature (Hayward Perflex EC-50/EC-75), bump the handle frequently during the conversion to redistribute the heavy residual load.
⛔ Pressure Gauge Reference
- Normal starting pressure: 10–20 PSI (varies by system)
- Clean/backwash threshold: 8–10 PSI above baseline (action required)
- Emergency shut-off: 30–40 PSI or higher — shut off the pump immediately to prevent explosive component separation or lid failure
Brand-Specific Equipment Instructions
Every major filter and salt system manufacturer has specific quirks during a biguanide conversion. Following the generic steps above gets you 80% of the way there — but the brand-specific details below are what separate a successful conversion from a costly callback.
Hayward (SwimClear™, Pro-Grid™, S-Series, Perflex®)
VariFlo™ Multiport Valve (S-Series sand, Pro-Grid DE): At conversion start, set the handle to RECIRCULATE when adding the initial high-dose chlorine. This bypasses the filter media and prevents immediate clogging. Switch to WASTE when vacuuming the Baqua-goo off the floor. After vacuuming, rinse, then return to FILTER. The VariFlo handle positions: Filter → Backwash → Rinse → Waste → Recirculate → Closed.
SwimClear™ Cartridge Filters (C2030–C7030): Use a 3/4″ socket wrench to loosen the clamp band nut — this filter does not use a simple hand-tighten band. When replacing cartridges, wipe the rim of both tank halves completely clean of any dust or debris before reassembling; even a small amount of grit can cause leaks under pressure. Tighten to spec, not by feel. Clean the cartridges when the pressure gauge rises 7–10 PSI above the green starting arrow.
Perflex® EC-50 / EC-75 Extended-Cycle DE Filters: These filters use a “bump” mechanism to redistribute the DE cake when flow drops. During conversion, the heavy biguanide load will rapidly cake the grids — bump the handle frequently (every hour if needed) rather than waiting for a pressure spike.
AquaRite Salt System (Post-Conversion): The “Inspect Cell” light flashes every 500 hours of operation as a maintenance reminder — this is normal and not an error (press and hold the diagnostic button 3–5 seconds to reset). “Check Salt” or “ADD SALT” triggers when salt drops below 2,400–3,000 ppm. Note: AquaRite is Hayward’s flagship inground salt system. The AquaTrol is Hayward’s above-ground system. Salt & Swim is a lower-cost inground line (e.g., Salt & Swim 3C for pools up to 30,000 gallons) — distinct from AquaRite’s full-featured control capabilities.
Pentair (Clean & Clear®, FNS® Plus, Quad D.E.®, Triton® II)
FNS® Plus / Quad D.E.® (Vertical Grid DE Filters): These filters use curved grids that maximize filtration area — but that geometry also makes them susceptible to “bridging” where biguanide residuals form a sticky dam across grid surfaces. Backwash for 3–5 minutes until the water in the sight glass runs completely clear, not just mostly clear. Incomplete backwashing during conversion will leave residual goo that reacts with chlorine for weeks afterward.
Clean & Clear® Plus (CCP240–CCP520) Cartridge Filters: Pentair’s manual is explicit: remove all oils and biguanide film with a commercial filter cleaner before any acid soaking. Acid soaking without that prior cleaning step will permanently set the biguanide residual into the polyester filter fibers and permanently restrict water flow. Soak in 1 cup dishwasher detergent per 5 gallons of water (or a commercial cleaner) for at least one hour — overnight is better.
If Mineral Scale Is Present: After the biguanide film is removed, soak in a 1:20 muriatic acid-to-water solution for 10 minutes, or until bubbling stops. Always add acid to water (never water to acid). Wear rubber gloves, safety glasses, and an N-95 mask.
IntelliChlor Salt System (Post-Conversion): The “COLD” or “LO” display activates when water temperature drops below 51°F–54°F, halting chlorine production — this is by design, not a malfunction. “Check Salt” triggers when salt falls below 2,400 ppm. Always add acid to water when cleaning the IntelliChlor cell; work in a well-ventilated area.
Jandy (CL/CV, DEV/DEL, JS Series)
SVLV8 Slide Valve (DEL Series): The Jandy slide valve is a two-position valve — the handle must be fully extended or fully depressed. It cannot be throttled or partially positioned. Any intermediate position damages the valve seat. This is different from Hayward’s rotary multiport — don’t treat it the same way.
DEV Series DE Filter Grid Disassembly: To remove the grid assembly for cleaning, unscrew the tie rod knob in the center of the manifold, then lift the manifold assembly off the grids using the molded handles. The grids are then accessible for inspection, soaking, and cleaning. Reassemble in reverse order, ensuring the tie rod knob is fully tightened before replacing the tank lid.
JS Sand Filters: Jandy specifies #20 silica sand in the 0.40mm–0.55mm range (per the JS Series installation manual; recommended brands include Wedron Silica and U.S. Silica). Using the wrong sand grade reduces filtration effectiveness. When replacing sand after conversion, Jandy recommends using the barrel unions (included with most Pro Series models) to allow for full teardown and interior tank inspection before refilling.
CXi™ Heater and Water Balance (Post-Conversion): Once you switch to chlorine, maintaining proper water balance becomes critical for heater longevity. Jandy requires a Langelier Saturation Index (LSI) between -0.3 and +0.3 (per Jandy JXi/LRZ heater manuals) to prevent corrosion of the copper heat exchanger; a slightly positive value is more acceptable than a negative one. Keep Free Chlorine at 1.0–3.0 ppm, pH at 7.2–7.6, Total Alkalinity at 100–150 ppm, and Calcium Hardness at 200–400 ppm. AquaPure salt systems display “LO” or “COLD” when water is below 51°F.
Zodiac / Jandy Saltwater Systems (AquaPure®, TruClear™)
Critical Prerequisite: All biguanide residuals must be fully cleared from the water before activating any salt chlorine generator. For the Jandy TruGuard system specifically, the manufacturer manual requires a complete pool drain and refill when converting from biguanide — the burn-out method alone is not permitted for TruGuard startups. Activating any cell with biguanide still present will contaminate the cell and create water chemistry problems that are difficult to resolve.
Cell Installation: The salt cell must be the last component in the equipment line before water returns to the pool. Installing it before the heater or filter means chlorine production corrodes upstream equipment. The controller mounts on a wall near the equipment pad; the cell is plumbed into the return line. Connect the flow sensor from cell to controller, check for leaks, then proceed.
Salt Dosing: Add approximately 200 lbs of pool-grade sodium chloride per 10,000 gallons to reach an initial level of 3,000–3,200 ppm. Use evaporated, granulated, food-quality salt or solar salt (99%+ pure NaCl). Never use iodized salt, rock salt, or salts with anti-caking agents above 0.1%, as these contain iron and will stain fittings.
Startup Timing: Broadcast salt around the pool edges and allow 24 hours for full dissolution with the pump running before activating the chlorine generator. Run the pump for several hours after activation to verify chlorine production. “Check Salt” or “ADD SALT” displays when salt falls below 2,400–3,000 ppm; annual booster treatments of 10–50 lbs per 10,000 gallons maintain optimal levels.
Converting to Saltwater: The Extra Steps
Going all the way to saltwater adds a layer of steps on top of the biguanide burn-out described above. The good news: you don’t have to drain the pool. The bad news: many pool owners are tempted to shortcut the biguanide removal phase because they assume draining is “the clean option.” It is — but it’s not required, and the risks of an improper drain (hydrostatic pressure, liner shrinkage, plaster cracking) often outweigh the benefits.
If you choose not to drain, complete the full burn-out process first. Only once Combined Chlorine (CC) is 0.5 ppm or below for two consecutive days should you move on to saltwater installation.
⛔ If You Choose to Drain: Critical Warning
Never fully drain a pool without accounting for hydrostatic pressure. An empty inground concrete pool can literally pop out of the ground if ground water pressure is high. Vinyl liners shrink when dry, cracking the material permanently. If draining, do so slowly, monitor the hydrostatic relief plug in the deep end, and keep a portion of water in the pool until you’re ready to refill immediately.
After completing the biguanide burn-out and replacing your filter media, here’s the saltwater conversion sequence:
- Balance water chemistry first — chlorine, alkalinity (100–150 ppm), pH (7.2–7.6), calcium hardness (200–400 ppm), then metals.
- Mount the controller on the wall near your equipment pad. Wire it per the manual — some systems use a GFCI plug; others wire to the pump timer.
- Plumb the salt cell as the last component in the return line, after the heater and filter. This prevents chlorine from corroding upstream equipment.
- Broadcast salt around the pool edges — approximately 200 lbs per 10,000 gallons for an initial level of 3,000–3,200 ppm. Run the pump continuously.
- Wait 24 hours for full salt dissolution before activating the generator.
- Activate the generator and verify chlorine production. Check for plumbing leaks at all new connections.
Common Mistakes and What They Cost
Most conversion failures trace back to one of five mistakes. Know them before you start — not after you’ve already made them.
| Mistake | What Happens | Repair Cost |
|---|---|---|
| Using TSP too early | TSP + biguanide film = permanent gum on filter media that cannot be removed | $100–$600 (full media replacement) |
| Skipping filter media replacement | Residual biguanide reacts with new chlorine → permanent cloudy water, poor filtration | $200–$800 |
| Improper pool drain | Hydrostatic pressure cracks plaster or pops pool from ground | $10,000+ |
| Shock in the skimmer | Chlorine + skimmer residue → explosive gas in confined space → filter system damage | $500–$1,500 |
| Stopping conversion mid-process | Bacteria converts CYA to ammonia → massive chlorine demand, water unsafe | Triple/quadruple shock dose required |
| Mixing different chlorine types | Dichlor + Cal-Hypo = violent reaction, fire or explosion risk | Injury, property damage |
One consequence worth highlighting separately: if you start the burn-out and then abandon the process for several weeks, bacteria in the pool can convert your cyanuric acid (CYA) into ammonia. For every 10 ppm of CYA that breaks down, the bacteria produces approximately 3.3 ppm of ammonia — and you’ll need 30+ ppm of cumulative FC to eliminate it. That’s an expensive hole to dig out of. Once you start, commit to finishing.
Safety Rules You Cannot Break
Every year, thousands of pool owners visit emergency rooms from chemical exposure. Most injuries happen because someone wasn’t wearing protection, or because they mixed chemicals without thinking. These rules are non-negotiable.
⛔ DANGER — These Mistakes Can Kill
- Never mix chemicals outside the pool — toxic gas or explosion risk. Add each chemical directly to pool water separately.
- Never add water to acid — always add acid to water to prevent violent boiling and splashing.
- Never mix different chlorine types — Dichlor + Cal-Hypo, Trichlor + anything else = fire/explosion.
- Never pour shock into the skimmer — if you have an automatic chlorinator, this combination creates explosive gas in a confined chamber.
- Never open a chlorinator that has been sealed with tablets inside — chlorine fumes are heavier than air; get to fresh air immediately if exposed.
Required PPE for every chemical handling session:
If you experience intense burning in your airways, difficulty breathing, chest tightness, or persistent nausea after handling pool chemicals, get to fresh air immediately — chlorine fumes are heavier than air, so move upwind and call 911 if symptoms persist.
After the Conversion: Balancing Your New Chlorine or Salt System
Once the conversion endpoint is confirmed (CC ≤ 0.5 ppm for two days, FC holding overnight), you’ve crossed the finish line. Now it’s time to set up your pool properly for long-term maintenance.
The first thing to do: add CYA (cyanuric acid) to 30–50 ppm. Stabilizer protects your free chlorine from UV degradation, dramatically reducing your chlorine consumption going forward. Without it, the high chlorine doses you used during conversion will be the norm rather than the exception.
| Parameter | Chlorine Pool | Salt/SWG Pool |
|---|---|---|
| Free Chlorine | 1.0–3.0 ppm | 1.0–3.0 ppm |
| pH | 7.2–7.6 | 7.2–7.6 |
| Total Alkalinity | 80–120 ppm | 100–150 ppm |
| Calcium Hardness | 200–400 ppm | 200–400 ppm |
| CYA (Stabilizer) | 30–50 ppm | 70–80 ppm (SWG) |
| LSI (Langelier Index) | -0.3 to +0.3 | -0.5 to +0.5 |
For ongoing chlorine maintenance in a traditional pool, a quality floating dispenser is the most hands-off way to maintain consistent FC levels between testing sessions — especially for pools running stabilized trichlor tablets.
Pool Chlorine Floater
$34.99
Maintain consistent trichlor tablet delivery after converting from biguanide. Adjustable flow rate, compatible with standard 3-inch chlorine tablets. Keeps your FC stable without daily dosing.
Post-Conversion Checklist
- ✓ CC ≤ 0.5 ppm confirmed for 2 consecutive days
- ✓ Filter media replaced (sand, cartridges, or DE grids)
- ✓ CYA added to 30–50 ppm (70–80 ppm for SWG)
- ✓ pH, alkalinity, and calcium hardness balanced to target ranges
- ✓ FC reduced to maintenance level (1–3 ppm)
- ✓ Salt added (SWG only) — 200 lbs/10,000 gal, 24-hr dissolution before activating
- ✓ LSI calculated and verified in range (-0.5 to +0.5)
- ✓ Routine maintenance schedule established (weekly test and adjust)
💡 Seasonal Note: Rain and Storms
Heavy rainfall introduces high organic loads and dilutes both chlorine and CYA. After any significant storm, increase your salt generator output temporarily or manually shock the pool to 5–15 ppm to prevent algae from getting a foothold in your newly-converted system. This is especially important in the first season after conversion when your pool is still equilibrating to chlorine chemistry.
Frequently Asked Questions
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Disclaimer
This guide is for educational purposes only. Pool chemistry, equipment configurations, and local regulations vary. Always read and follow manufacturer instructions for your specific equipment. When in doubt, consult a licensed pool professional. ProTuff Products is not responsible for damage, injury, or loss resulting from the use of this information.
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