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A cloudy hot tub is pretty much going to happen to all hot tub owners some time or other. In fact how to fix a cloudy tub is one of our most frequently asked questions.

Fixing a cloudy hot tub is usually quite easy, but stopping it occurring is even better. We are going to take a deep dive through the causes and fixes first, and finally how to stop the cloudy hot tub problem reoccurring.

Common Causes Of Cloudy Hot Tub Water


This is a more common cause of cloudy hot tub water than you might think. If you are struggling to get the crystal clear and sparkling water after a water top up or after the initial fill then micro solids could be a contributing factor.

Checking and adjusting our chemical balance as well as good hot tub filtration should correct this after a frustrating day or two. It may not eliminate everything but we always recommend using an inexpensive inline filtration system when starting out, refilling or topping up your hot tub.

For a few dollars it just makes sense to start out your hot tub with the “cleanest” water you can. This way you’ve a blank canvas to build your desired sanitation profile on.

Camco Water Filter With Hose Connector
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Camco Water Filter With Hose Connector
  • 6-Step Water Filtration System: Filter hose washer, pre-filtration layer for debris, premium activated carbon filter, superior KDF formulation protecting against bacteria, a post-filtration layer, and spun polypropylene for 20-micron particle removal.


Particularly in hard water areas pay careful attention to calcium levels and total alkalinity readings. If they slip out of balance they can lead to a cloudy hot tub.

Prepare to take action is the TA reading exceeds 150PPM. It’s an easy enough to fix alkalinity it just requires adding some additional chemicals to bring your hot tub water back to its sparkling best.

Leisure Time ZIQ Liquid Spa Down Balancer for Spas and Hot Tubs, 32 fl oz
247 Reviews
Leisure Time ZIQ Liquid Spa Down Balancer for Spas and Hot Tubs, 32 fl oz
  • BENEFITS: Lowers the pH and total alkalinity in spa water

Calcium levels can quickly rise if your hot tub lives in a hard water area and needs frequent topping up. If it creeps over 400PPM then it’s time to take action. Unfortunately this is a trickier problem to solve.

The accepted wisdom is to partially drain the hot tub and top up with soft water. 

Well that’s not straight forward if the source water that has caused the problem is high in calcium in the first place. Help is at hand though by using a calcium blocking filter that attaches to your garden hose. The one we recommend not only filters out calcium but other undesirable elements.

Hydro Life 52804 Pool Pre-Fill Water Filter with Calcium Blocker, White
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Hydro Life 52804 Pool Pre-Fill Water Filter with Calcium Blocker, White
  • Specifically designed to reduce the levels of calcium, as well as reduce heavy metals, chlorine, chloramines and volatile organic compounds to make balancing chemicals easier


Checking the filter is surely the first thing you’ve done when trying to solve your cloudy hot tub problem. But the first thing to visually check is if the pump working efficiently and the water is actually being filtered and circulated strongly as it should be.

Next pull the filter and either clean it or replace it. Make sure it’s correctly seated and not being bypassed.

Lastly you may need to increase the time your hot tub is being filtered typically this will be in the summer months for outdoor hot tubs. If hot tub usage goes up then filter pump hours need to be increased.

Leisure Time O Filter Clean Cartridge Cleaner for Spas and Hot Tubs, 1-Pack
1,980 Reviews
Leisure Time O Filter Clean Cartridge Cleaner for Spas and Hot Tubs, 1-Pack
  • BENEFITS: Improves the efficiency and life of the filter


Letting sanitiser levels drop out of the recommended envelope can cause all kinds of problems. Cloudy water is just one of them. The term “cloudy hot tub” can sometimes mask what often is really happening and that’s that algae starting to appear and go into suspension in your tub.

Yikes!! Keep those sanitiser levels up folks!

Sanitiser levels can dip dramatically and cause cloudy spa hot tub water after high bather usage. If more folks than usual are enjoying your hot tub then definitely do a spot chemical level check and adjust back up to stop your hot tub clouding up.

Typically aim for 2 – 4 PPM for Bromine and 3 -5 PPM for Chlorine.


Typically biofilm occurs if the hot has been left unused for a period of time with the pump not running. An unpleasant bacteria can build up in the plumbing lines and produce a slimy internal coating. It can build up surprising quickly, and in some cases can produce floating slime slicks on the surface of the water after the pumps have been restarted.

As you can imagine this is not just visually unpleasant sight but also a real health risk that needs to be taken very seriously.

In all cases of suspected biofilm we always recommend using a spa line flush product then draining the hot tub and performing a careful deep clean before refilling.


No matter how meticulous you are in maintaining excellent chemical properties in your hot tub water sooner or later the sanitation system will become overwhelmed and the water will become cloudy.

It might take a few months or longer but all hot tubs need the water changed out at this point. Foaming and cloudy spa water are obvious signals that perhaps the water is “past it’s sell by date” and simply just needs to be replaced. We have written a full article here on when to change out hot tub water >>


  • Remember to shower before stepping into the hot tub for a soak. If your tub is outside pay attention that no debris is transferred from your feet to the hot tub water.
  • On water changes or initial fill use filtered water to give a clean base to build your chemical profile from.
  • When changing your hot tub water always use a plumbing line flush prior to dumping the water. This stops hidden and very unpleasant bacterial problems building up in the hot tube tubes.
  • Don’t just fall into a chemical and sanitiser routine. Always do regular water quality checks and adjust based on results. This is especially important during high usage seasons. Don’t guess!! Deal with your tub water based on real data.
  • Inspect and clean or replace filter regularly. This is one of your first line defences.
  • Visually check water flow circulation. If water flow into the hot seems to be less than normal it could be an overloaded filter or indicate pump problems.
  • Adjust the time the filter pump is running to correspond with hot tub usage. A cloudy hot tub is often just caused by lack of pump running time.

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