How To Acid Clean A Salt Cell: A Step-By-Step Protocol From A CPO 

By Mike Ruff — Owner, Daytona's Best Pool Service. CPO® & PHTA Certified. Licensed and Insured.

Your salt cell is a $400-900 piece of equipment that does the actual sanitization work in your pool. Take care of it and it'll last 5-7 years. Ignore it and you'll be writing a check for a new one in three.

The single most important thing you can do to extend cell life — and the thing most saltwater pool owners either skip entirely or do incorrectly — is quarterly acid cleaning. Every 3-4 months. Even if you don't see visible scale yet. Calcium buildup on the cell plates is the number-one cause of premature cell failure, and the acid cleaning process is the only way to remove it.

I've cleaned thousands of cells over seven years running Daytona's Best Pool Service. I'm a CPO® through the Pool & Hot Tub Alliance, fully licensed and insured. The protocol below is exactly what I do on real service calls. Read all of it before you start. Wear the safety gear. Don't skip the order.

Why You Need To Do This At All

Your salt cell contains a series of parallel metal plates inside a clear plastic housing. Those plates are titanium with a thin coating of precious metals (typically ruthenium oxide). The coating is what does the electrochemical work — splitting salt into sodium and chlorine.

The plates are exposed to your pool water 24/7 while the pump runs. Your pool water contains calcium. Over time, calcium deposits build up on the plates as scale — usually visible as white, off-white, or beige crusty buildup.

That scale layer does two destructive things. First, it physically blocks water from contacting the plates, which reduces chlorine production dramatically. Second, the cell has to work harder to produce normal output through a scaled surface, which accelerates wear on the precious-metal coating. A scaled cell burns through its rated lifespan faster than a clean cell.

The math is brutal: a cell that should last 5 years with proper maintenance often fails at 3 years if scale is never cleaned. That's roughly $150-250 a year in premature equipment cost, on top of the gradually worsening chlorine production that causes owners to "fix" the symptom by buying chlorine boosters they don't need.

A 15-minute acid clean every quarter prevents all of that.

Before You Start: Safety Is Not Optional

Muriatic acid is hydrochloric acid in diluted form. It is genuinely dangerous if handled carelessly. Specifically:

It will burn your skin on direct contact. The burn isn't immediate or even painful at first — you'll feel a slight warmth, then realize 30 seconds later that your skin is going white. By the time it hurts, the damage is done.

It will blind you permanently if it splashes in your eyes. Not "irritate." Blind. Pool acid burns to the eye are one of the most preventable serious injuries in residential pool ownership.

It releases fumes that damage lungs with repeated exposure. The fumes are heavier than air and pool around containers — bending over a bucket of acid to look inside puts your face exactly where the fumes concentrate.

It reacts violently with anything containing chlorine or oxidizers. Never store muriatic acid near pool chlorine, shock products, or household bleach. Even small spills between adjacent containers can release chlorine gas.

You need, before you start:

Chemical-resistant gloves (nitrile or neoprene — not standard latex dishwashing gloves)

Full safety goggles (not safety glasses — actual sealed goggles that prevent splash from the sides)

Long sleeves and long pants

Closed-toe shoes (no flip-flops or sandals)

A clean source of running water nearby (a hose with a nozzle works)

Work outdoors only. Never indoors, never in a garage, never in an enclosed pool equipment shed. Open air, with a breeze.

If you are pregnant, have respiratory issues, or have any history of chemical sensitivity, don't do this yourself. Hire a pool tech for $40-75. Don't gamble.

When To Clean

There are four windows when acid cleaning makes sense:

Every 3-4 months as scheduled preventive maintenance, regardless of whether you see scale yet. This is the routine that prevents the cell from ever developing heavy buildup in the first place. Calendar reminder, every quarter, treat it as non-negotiable.

Immediately when you see visible scale. Pull the cell, look down through it. If the plates show white, off-white, or beige buildup, clean now. Don't wait for the next scheduled quarter.

When chlorine output drops without an obvious other cause. If your salt, CYA, pump runtime, and cell output settings are all in spec but chlorine production is below normal, scale is the most likely culprit.

After any "inspect cell" or low-output error code from your control panel. The cell is telling you to look at it.

What You'll Need

Get all of this together before you start. You don't want to be hunting for a tool with acid on your hands.

A bottle of muriatic acid, 31.45% concentration (the standard pool-grade product). One gallon is way more than you need for a single cleaning — but it's the smallest size most stores sell.

A clean 5-gallon bucket, ideally one dedicated to this purpose. Plastic only. Never glass.

A cell stand or cell cap. Most salt systems come with a cap (the small plastic disc that screws onto the end of the cell). If yours didn't come with one, or you've lost it, both Hayward and Pentair sell aftermarket stands for $15-25. You can also improvise with a clean plastic cap that fits over the end of the cell.

A garden hose with a sprayer nozzle.

Chemical-resistant gloves and safety goggles (covered above).

A measuring container that holds at least 16 ounces. A cheap plastic measuring cup or a graduated bucket works.

The Step-By-Step Protocol

Step 1 — Turn Off Power At The Breaker

Not just at the pump timer. At the breaker. The salt cell shares the pump circuit on most installations, and you absolutely do not want any voltage going to those plates while you're handling them with acid.

Walk to your breaker panel. Find the pool circuit. Flip it off. Verify by trying to start the pump from the timer — nothing should happen.

Step 2 — Remove The Cell From The Plumbing

Look at your equipment pad. The cell is the transparent or translucent housing in the plumbing line, usually downstream of the filter and just before the water heads back to the pool. It's held in by two large unions — one on each end.

Unscrew the unions by hand. They should turn without tools. If they're seized, a strap wrench helps; never use a metal pipe wrench, which can crack the housing.

Water will drain from the cell as you remove it. Have a small bucket or rag ready to catch it. Set the cell down on a flat surface where you can work on it.

Step 3 — Inspect The Plates

Look down through the cell. The interior should be clearly visible — you'll see the parallel metal plates with water channels between them.

What you might see:

Clean plates: Shiny metallic surface, water channels clearly visible all the way through. Your cell is in good shape. You can still acid clean preventively, but a brief 5-7 minute soak is enough — don't extend the time on a clean cell, because the acid removes a tiny amount of the coating every time and an over-long soak on an already-clean cell wears it for no benefit.

Light scale: Thin white or off-white film on the plates. This is normal accumulation; routine cleaning will remove it in 10 minutes.

Heavy scale: Thick white crusty buildup, possibly bridging between plates. This indicates the cell has gone too long without cleaning. Full 15-minute soak required; may need a second cycle.

Damaged plates: Pitting, flaking coating, warping, or plates that look different from each other. This means cell end-of-life. Acid cleaning won't restore plates that have lost their coating. If you see this and your cell is over 4 years old, plan for replacement.

Step 4 — Mix The Cleaning Solution

This is the step that hurts people who get it wrong. Pay attention.

You will mix muriatic acid with water in a 4:1 ratio — four parts water to one part acid.

ALWAYS ADD ACID TO WATER. NEVER ADD WATER TO ACID.

Adding water to undiluted acid causes a violent exothermic reaction. The mixture can boil instantly, spraying hot acid out of the container. Adding acid to water dilutes safely as it goes in.

For a typical residential cell, you need about a half-gallon of mixed solution. That's:

• 2 quarts (64 oz) of clean water poured first into the bucket

• Then 16 oz (one cup) of muriatic acid poured slowly into the water

You'll see a brief fizz as the acid contacts the water and small wisps of vapor. That's normal. Don't bend over the bucket to look. Stand back.

Stir gently with a plastic or wooden stirring stick to mix. Never metal — acid attacks metal.

Step 5 — Set Up The Cell For Cleaning

Take your cell. Cap one end with the cell cap or set it into the cleaning stand so it stands vertically with one end sealed.

Place the capped end facing down. The open end should be facing up.

You're going to fill the cell with the acid solution like a vase. The cap holds the solution inside the cell while it works on the plates.

Step 6 — Fill The Cell With Solution

Slowly pour the diluted acid solution from your bucket into the open top of the cell. Pour slowly — fast pouring causes the solution to splash up the sides and out the top.

Fill until the solution covers all the plates. You don't need to fill to the very top of the cell housing; just enough that the plates are fully submerged.

You'll see immediate bubbling. That's the reaction between the acid and the calcium scale. The bubbles are carbon dioxide being released as the calcium carbonate dissolves. This is exactly what you want to see — visible bubbling means the cleaning is working.

If you see no bubbling at all, your cell likely had minimal scale; you can shorten the soak time. If you see vigorous, foamy bubbling that threatens to overflow the top of the cell, the cell had significant scale and the reaction is intense. Don't add more solution; let it work.

Step 7 — Wait 10-15 Minutes

This is the actual cleaning. Set a timer. Step back from the bucket. Don't bend over the cell to watch.

For light scale, 10 minutes is plenty.

For moderate scale, 12-15 minutes.

For heavy scale, you may need a second cycle — drain this batch, mix a fresh batch, repeat.

Do not exceed 15 minutes in a single soak. Extended exposure starts to remove the precious-metal coating from the plates, which is the part that does the actual electrochemistry. Cleaning the scale should not become destroying the cell.

You'll see the bubbling gradually slow down as the scale dissolves. When the bubbling is largely stopped — usually somewhere between 8 and 12 minutes — the cleaning is essentially complete.

Step 8 — Drain The Spent Solution Carefully

Pour the spent solution out of the cell, away from yourself. The solution is still acidic — gloves and goggles stay on.

Where to drain the spent acid solution matters. Options:

Best: Into a 5-gallon bucket of water (which dilutes it further), then poured slowly into a sanitary sewer or floor drain.

Acceptable: Into a non-edible landscape area at least 50 feet from any water body, with significant water rinse afterward.

Never: Into your pool, into a vegetable garden, into a septic system, into a storm drain (illegal in most jurisdictions), or onto concrete that you care about (it will etch the surface).

Step 9 — Rinse Thoroughly

Take the cell to your garden hose. Spray clean water through the cell in both directions — first one way, then the other — for at least 60 seconds total.

You want to rinse out every trace of acid residue. Any acid that makes it back into your pool system can damage other components, and any acid that splashes you while you're reinstalling the cell will burn through your gloves over time.

Look down through the cell after rinsing. The plates should look noticeably cleaner than before — typically brighter, with clearer water channels between them. If you still see significant scale, run a second cycle (steps 4-8 again).

Step 10 — Reinstall The Cell

Place the cell back into its position in the plumbing. Make sure the flow direction arrow on the cell matches the actual flow direction in your plumbing (water enters one end and exits the other; reversed installation causes flow errors and reduced effectiveness).

Hand-tighten the unions. Snug them, but don't over-tighten — these unions seal with o-rings, not with mechanical force, and over-tightening can crack the housing.

Step 11 — Power On And Verify

Walk to the breaker and turn the pool circuit back on. Start the pump from the timer.

For the first few minutes, watch the cell connections. You're checking for any water seeping at the unions. A small drip means a union needs another quarter turn; a steady stream means the union is cross-threaded or an o-ring is damaged.

Once the pump has run for 10-15 minutes with no leaks, check the control panel. The cell should report normal operation — no error codes, salt reading in range, output operating as set.

Run the pump for at least an hour before testing the water. Then verify chlorine production with a test kit. If it improved noticeably from before the cleaning, the cell is working as intended.

Step 12 — Store Or Dispose Of Remaining Acid

If you have unused muriatic acid in the bottle, store it properly:

In its original container with the cap tightly sealed.

In a cool, dry, well-ventilated area away from direct sunlight.

Far away from any chlorine, shock, or oxidizing chemicals. Different shelf in your shed. Different cabinet. Never adjacent.

Locked up if you have children or pets in the area.

If you need to dispose of remaining acid, don't pour it down the drain. Take it to your local hazardous waste facility. Most municipal household chemical drop-off sites accept it for free.

A Few Things That Can Go Wrong

You see no bubbling at all when the acid contacts the plates. Either your cell genuinely had no scale (uncommon if it's been more than a quarter since the last cleaning), or you accidentally diluted the acid too much. Test the mixture with a small piece of calcium scale (a small chip of pool tile sometimes works) — it should fizz visibly. If not, mix a fresh batch with proper ratios.

The cell leaks after reinstallation. Almost always a union issue. Power off, remove the cell, inspect the o-rings on both ends. If they look pinched, dirty, or worn, replace them ($5-10 at any pool store). Reinstall.

Cell still shows reduced output after cleaning. Possibilities: the scale was so heavy that one cleaning didn't get it all (run a second cycle); the cell is past end-of-life and needs replacement; or the actual problem is somewhere else (low salt, low CYA, wrong cell output setting). Work through the troubleshooting checklist before deciding it's the cell.

Control panel throws a flow error on restart. Air in the line, sometimes. Most pumps have a strainer cover with a bleed screw — loosen briefly to let air escape, then re-tighten with the pump running.

Acid splash on skin or eyes during the process. Immediate flood with clean water for at least 15 minutes. Eyes: keep flushing until you can get medical attention. Skin: if redness persists after 15 minutes of rinsing, see a doctor. Don't tough it out.

How Often, Realistically

For most residential pools in average-hardness water, every 90 days is the right interval. Mark it on a calendar. Treat it as non-negotiable.

If you're in an area with hard fill water (above 300 ppm calcium), or if your pool has been running with elevated pH for an extended period, scale forms faster. You may need to clean every 60-75 days. Check the cell visually each month — if you can see scale, it's time.

If you're in soft water and your chemistry has been well-balanced, you might stretch to every 4-5 months. But err on the side of more frequent rather than less.

The owners I service who never have cell problems are the ones who clean on schedule. The ones who call me complaining about replacing cells every 3 years are the ones who acid cleaned twice ever and called it done.

The Bigger Picture

Acid cleaning is one piece of saltwater pool maintenance — the most important single piece for cell longevity, but only part of the system. The chemistry that prevents heavy scaling in the first place, the seasonal pump and output adjustments that keep chlorine demand matched to supply, the troubleshooting protocols when something does go wrong — all of that compounds into either a low-effort saltwater pool you barely think about, or a high-frustration system that ages prematurely and costs more than it should.

The complete saltwater pool maintenance system — chemistry differences from chlorine pools, target ranges for every parameter, the weekly and seasonal routine, the full troubleshooting protocols with control panel error code references, equipment compatibility guide, and the printable annual maintenance calendar — is in The Saltwater Pool Owner's Complete Guide ($19.97). Thirty-two pages, written by a working CPO. The acid cleaning chapter is one section of the larger system.

When To Skip The DIY And Call A Pro

Acid cleaning is genuinely DIY-friendly for most owners. But there are situations where calling a licensed pool pro is the right call:

If your cell is still under manufacturer warranty, check the warranty terms before doing anything that involves chemical cleaning. Some manufacturers require professional service for warranty claims to remain valid.

If you've never handled muriatic acid before and the safety procedures feel overwhelming, hire it out for the first time. Watch how the tech does it. Then do it yourself next quarter.

If your cell has plate damage visible during inspection (pitting, flaking, warping), don't waste time cleaning it. Get a pro's assessment and a quote for replacement.

If you're in the Daytona Beach, Port Orange, or New Smyrna area and want it handled for you, that's exactly what Daytona's Best Pool Service does. Reach out through the site and we'll take care of it on a service call.

For everyone else: the protocol works. The safety procedures are non-negotiable. The 15 minutes of focused work every 90 days will pay you back many times over in cell life and consistent chlorine production.

Get the complete Saltwater Pool Owner's Guide for $19.97 →

And before you start: get a real test kit. You'll want to verify chlorine production before and after cleaning to confirm the work was effective, and the Taylor K-2006 reads all the saltwater chemistry parameters you actually need.

You've got this.

— Mike Ruff Owner, Daytona's Best Pool Service CPO® & PHTA Certified · Licensed and Insured