Does anyone else have cloudy hot tub water even after cleaning filters?

K

Katherine Morgan

Member
Hey all, not sure what’s going on lately. The water’s been looking kinda cloudy the past few days, even though I cleaned the filters and shocked it. The chlorine level looks okay on the test strip, and nothing smells off.

We’ve only used it a couple of times this week, too. I haven’t changed anything in terms of routine, so I’m kinda stuck. Maybe a buildup in the lines or something? I don't know, just wondering if anyone’s had this happen and figured it out.
 
Cloudy water can sometimes hang around even when your chlorine and filters seem fine. I’d try testing your pH and alkalinity just to be sure they’re balanced. High pH or low alkalinity can make water look dull or cloudy. Also, try running the jets longer to improve circulation, and brush the seats and walls to break up any hidden biofilm that might be lingering in the plumbing.
 
Happened to me once when my water looked clean on paper but still cloudy. Ended up being build-up in the plumbing lines. I ran a line flush product through the system, drained, and refilled. After that, it cleared right up. Sometimes it’s biofilm in the places your filters and sanitizer can’t reach. If it’s been a few months, a drain and refill might be the easiest fix.
 
I ran into the same thing not long ago, and it turned out to be my calcium hardness levels. When they were too low, the water looked cloudy no matter how much I shocked or cleaned the filters. Once I brought the hardness up into range, the water cleared within a day. Another thing I noticed is that lotions and oils from skin can hang around and cause cloudiness even with sanitizer present, so I started using a scum sponge to soak that stuff up. Both changes made a big difference for me.
 
I had a similar situation once where everything looked balanced but the water stayed cloudy. In my case, it came down to circulation time. The pump wasn’t running long enough each day to really filter everything out. After I bumped up the run time and made sure the cover was kept on whenever it wasn’t in use, the water cleared a lot faster. Another small trick that helped was giving the water a quick rinse with a handheld skimmer net to grab any fine particles floating around. Sometimes it’s just the little things adding up.
 
I’ve had this too water suddenly cloudy. I’d do a quick test, run the pump/jets longer, and rinse the filter. If it’s still stubborn, I drain and refill problem solved.
 
I ran into the same thing not long ago and it turned out to be my calcium hardness. My water stayed cloudy no matter how much I cleaned the filters or used shock. I actually had an aquadoc chlorine starter kit on hand that had the calcium increaser in it, so I used that and it cleared up in like a day. I also started using a scum sponge to soak up lotions and oils and that helped way more than I expected.
 
I’ve had this happen, and it often means there’s something like biofilm or fine debris in the lines, even if the chlorine is fine. I solved it by using aquadoc jet line cleaner to clear out any buildup, then I followed up with aquadoc water clarifier to clear the cloudiness. That combo really helped me get the water clear again.
 
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Yeah, I’ve had that exact head-scratcher and it’s annoying because on paper everything looks fine. Filters clean, sanitizer reading okay, shock done, but the water still has that dull, hazy look that won’t quite clear. Makes you start second-guessing everything.

What was happening in my tub was a mix of fine particles plus chemistry that was just barely off. My alkalinity had slipped low without me noticing, so even though chlorine was present, it wasn’t really doing its job efficiently. That alone can keep tiny stuff suspended instead of letting it filter out. On top of that, oils from a couple short soaks were hanging around and the filter pressure was creeping up faster than usual, which told me the filter was catching junk but not fast enough to clear the water.

What finally worked was fixing the alkalinity floor first so the pH stopped drifting, then using a small dose of water clarifier from aquadoc. Not a dump-and-pray amount, just enough to help the fine particles clump so the filter could actually grab them. I let the circulation run longer than normal and stayed out of the tub for a day. By the next evening the water went from cloudy to that clear, glassy look again. If it comes back quickly after that, then yeah, line buildup might be the next thing to look at, but for me it never got that far.

Cloudy water with “normal” test results is usually the tub telling you something’s slightly out of balance, not that everything’s broken. Anyone else notice their water looks clear again right after fixing alkalinity, even before adding anything else?
 
i’ve had this exact thing happen and for me it wasn’t chlorine at all, it was buildup in the lines slowly clouding the water even though tests looked fine, what fixed it was running a purge with aquadoc jet line cleaner and then keeping things steady after with aquadoc weekly enzyme from mavaquadoc, once the hidden gunk was gone the water cleared up and stopped getting cloudy for no obvious reason.
 
From my experience, situations like this are rarely caused by one big issue, it’s usually small things adding up. The water can look fine on paper but still have fine particles hanging around. I’ve dealt with this before, and once I extended circulation for a few days and cleaned spots that don’t usually get attention, the clarity slowly came back without drastic steps.
 
I almost skipped replying because a lot of good angles are already covered, but there’s one thing that fooled me for weeks.

On my old Sundance 680 series tub, I kept getting that light cloudiness even with clean filters and chlorine sitting right around 3 to 4 ppm. What I didn’t catch at first was my saturation index was drifting slightly negative because calcium hardness was lower than I thought. The water wasn’t scaling or anything dramatic, it just had that flat, hazy look that wouldn’t polish out no matter how long I ran the jets.

I brought calcium up slowly, made sure alkalinity wasn’t sitting too low, and let it circulate for a full day. No extra products, no drain. The difference was subtle at first, then it just clicked into that clear, glassy look. Also noticed my filter pressure stayed more stable after that instead of creeping up every couple days, which tells me the water balance was helping the filter actually do its job.

If your numbers “look fine,” it might be worth double checking the actual ranges, not just whether they’re in the green box on a strip. Strips can miss small drifts that matter in a hot tub because the water volume is so small.

Anyone else see clarity improve just from dialing in calcium and alkalinity without changing anything else?
 
I’ve had this exact scenario and it drove me crazy because every test said I was “fine” but the water still looked dull.

One thing I didn’t see mentioned much is combined chlorine. Test strips will show free chlorine in range, but they don’t always tell you if you’ve got 0.5 to 1 ppm of combined chlorine hanging around. In a small spa, that’s enough to keep the water looking tired even if it doesn’t smell strong. When I finally checked with a drop kit, my combined chlorine was higher than I expected.

What fixed it for me wasn’t just a quick shock and done. I brought chlorine up to the higher end of the safe range and held it there for a full day with the cover open and good circulation. I also kept the air controls mostly closed so I wasn’t constantly whipping everything into suspension. The water actually looked worse for a few hours, kind of milky, then the filter pressure bumped up about 2 psi and by the next morning it was noticeably clearer.

Another small thing, check your actual water age. Even with light use, a 300 to 500 gallon tub accumulates dissolved solids fast. If it’s been a few months and you’ve mostly been topping off instead of draining, the water can just get “loaded.” At that point clarity becomes harder to maintain even when balance looks okay.

If you can, post your free chlorine, combined chlorine if you have it, pH, alkalinity, calcium hardness, and how old the water is. Usually the missing piece shows up once you look at the full picture instead of just the sanitizer number.
 
I almost didn’t jump in because a lot of the big causes have already been covered, but there’s one thing that caught me off guard once and it sounds similar.

My tub had that same cloudy look even after cleaning the filter and shocking. Numbers looked fine on strips, chlorine around 3 ppm, pH somewhere in the mid 7s. What I eventually noticed was the water looked clearer while the pump was running and then hazy again after it sat for a while. That usually means the filter is catching some stuff, just not fast enough to polish the water.

When I checked closer, my filter pressure had only climbed about 2 psi above normal, which didn’t seem like much, but the cartridge was still partially blinded with oils from a couple recent soaks. Even though it looked clean after a rinse, the fine particles were slipping through. I did a deeper soak clean on the cartridge and let the circulation run longer for a day or two. After that the water slowly went from dull to that clear “glassy” look again.

Another thing worth watching is your alkalinity floor. If TA drifts a little low, pH can bounce around during use and that makes sanitizer less effective even though the strip still says you’re in range. Hot tubs are small enough that little shifts like that show up as cloudiness pretty quickly.

If the water looks better while the jets are running but hazy when it settles, that’s usually a sign it’s just a filtration and stability issue rather than something major in the plumbing. How long are you running your filtration cycle each day? Sometimes bumping it up a bit helps the filter finally win the battle.
 
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