Pool Turning Purple After Soda Ash? In-Depth Guide to Causes, Expert Fixes, and Long-Term Prevention from Pool Service Pros
- Ethan Redick
- Jan 26
- 4 min read
Man, if you've ever added a big scoop of soda ash to bring your pH back up after the water got too acidic—maybe from a ton of evaporation, kids splashing nonstop, or just forgetting to check for a week—and then walked out the next morning to find your pool looking like someone poured in grape Kool-Aid powder, you're not losing your mind. That purple haze or those weird purple blotches and grit everywhere is super common, and it's almost always the same story: metals in the water freaking out from the fast pH jump.
I've seen this on so many pools over the years. Homeowners think they're doing the right thing with a quick pH fix, but soda ash hits hard and fast, and boom—purple nightmare. At SplashTech, we get called out for this exact thing way more than you'd expect. Good news is it's fixable without draining the whole pool most of the time, and once you understand what's going on, you can stop it from happening again. Let's walk through it like we're standing next to the equipment pad talking it out.
Why Soda Ash Turns Your Pool Purple (The Real Chemistry, No BS)
Soda ash (sodium carbonate) is great for bumping pH and alkalinity when things drop too low—happens all the time when it's hot, water evaporates fast, or you add too much acid chasing algae. Problem is, people tend to add way too much at once because they want quick results. That creates a sharp spike: pH can jump from 6.8–7.0 up to 8.2+ in spots before it mixes evenly.
That sudden swing does two bad things:
It messes with the water's balance (Langelier Saturation Index goes nuts for a minute), which can cloud things up with tiny calcium particles.
Way more importantly, it oxidizes any trace metals hanging around dissolved in the water.
The two big troublemakers are:
Manganese – Sneaky one from well water or even some city supplies. Invisible when pH is normal, but crank it up fast and it turns into hazy purple-lavender clouds or dark gritty deposits. Looks almost smoky at first, then settles.
Copper cyanurate – This is the one that gives you those bright purple crystals or reddish-purple stains stuck to the tile line, steps, skimmer baskets, and deep end. Happens when you've got high cyanuric acid (CYA/stabilizer—super easy to build up past 80–100 ppm if you're using tabs or dichlor shock all summer) plus even a tiny bit of copper (from old heaters, certain algaecides, corroding pipes, or fill water). The high CYA grabs the copper, forms this funky compound, and soda ash's pH kick makes it crash out as purple gunk.
High CYA makes everything worse because it locks the copper in place, and a big pH move shoves it right onto your surfaces. Ignore it long enough and those stains etch in—then you're looking at an acid wash or worse.
How to Tell Which Purple You're Dealing With
Hazy purple all through the water, maybe some blackish grit? Probably manganese.
Bright purple/red crystals, powdery stuff in baskets, blotchy stains on walls/steps? Copper cyanurate, almost every time.
Either way, if it's purple after soda ash, metals + rapid pH change is the culprit 9 times out of 10.
Step-by-Step: How We Actually Fix It (What Works on Real Pools)
Don't panic and start throwing more chemicals—that usually makes the metals oxidize even harder. Here's the playbook we run every time:
Stop everything. No more pH up, no shock, nothing.
Test properly. Grab a real kit (Taylor K-2006 or FAS-DPD drop style—strips lie about metals and CYA). Check pH, TA, CYA, calcium, metals if you can. Goal first: ease pH down to 7.2–7.4 with muriatic acid, slow and diluted so you don't swing the other way.
Brush like crazy. Hit walls, steps, floor, tile line hard to knock loose whatever's stuck. Vacuum to waste if you can—don't just send the purple junk right back through the filter.
If CYA is jacked (over 80–100 ppm), you've gotta dilute. Drain 25–50% (figure it based on your test), refill, retest. This is the only fast way to drop CYA and metals together. Yeah, it feels like a waste, but it's cheaper than a new surface.
Hit it with a good sequestrant/chelator. Stuff that actually works:
Jack's Magic Purple Stuff or Blue Stuff (solid for manganese and copper).
CuLator PowerPak (changes color when it grabs metals—satisfying to watch).
Orenda SC-1000 or Natural Chemistry Metal Free (long-lasting, phosphate-free). Dose heavy per the bottle, run the pump nonstop 2–3 days, backwash/clean filter every time pressure climbs 8–10 psi.
Once haze drops and metals are bound up, shock with straight liquid chlorine (no copper algaecide crap). Then creep pH and TA back up—use baking soda for TA so you don't repeat the soda ash mistake.
Stubborn stains left behind? Spot-treat with ascorbic acid paste (crushed Vitamin C tablets + water) or a commercial stain remover. Rub gently, let sit, brush off. If it's etched bad, call pros for an acid wash.
How to Never See Purple Again (Real Prevention That Sticks)
Raise pH slow. Small doses, pre-dissolve soda ash in a bucket first—never dump straight in.
Test weekly. Catch low pH before it gets ugly.
Keep CYA in check (40–60 ppm sweet spot). Switch to liquid chlorine or salt if tabs are killing you.
Run sequestrant weekly if your fill water has metals—cheap insurance.
Ditch copper-based algaecides unless you really need 'em.
Get regular pool service. A good tech spots high CYA or metals early, adjusts gradually, and saves you from those panic DIY moves.
Why Pool Service Pros Handle This Better Than Most DIY Attempts
Look, we've all tried the quick fix and ended up with a bigger mess. SplashTech techs show up with the right tests, the heavy-duty sequestrants, and the experience to know when it's manganese vs. copper cyanurate vs. both. Whether it's a one-off purple disaster or you want weekly pool service so this never happens again (Basic keeps it simple, Pro throws in deeper cleans, storm priority, and metal control), we get it done right.
If your pool's gone purple or you're tired of guessing on chemistry, hit us up for a free consultation. We'll come out, figure out exactly what's up, fix it fast, and get you set so your water stays clear and swimmable—no more surprises.
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