Cloudy Hot Tub Water – Causes, Cure, and Prevention

Owning a hot tub provides a source for relaxation and comfort. But like many good things in life, owning a hot tub requires regular maintenance to ensure problems don’t arise. If you’ve never thought to yourself, ‘my hot tub water is cloudy,’ consider yourself lucky. It probably means you’re following a good maintenance regimen. Still, the appearance of cloudy hot tub water is a common issue many spa owners run into.

Having cloudy hot tub water can be frustrating, particularly because it can result from many different factors. More troubling is that after speaking with your hot tub company, looking up solutions online, and watching countless YouTube videos, every source offers a different answer to the problem.

This deep dive into the causes and cures of cloudy hot tub water and how you can prevent it in the future will alleviate some of your confusion.


A number of factors can contribute to cloudy hot tub water. The following are the most common causes that can make your hot tub cloudy and foamy:

  • Filling the hot tub with cloudy water
  • High pH and alkalinity of the fill water
  • Dirty filters or insufficient filtration
  • Oxidizing minerals in the water
  • Poor hot tub sanitation
  • Hot tub contamination
  • The removal of accumulated buildup in the plumbing
  • Bathing suit dyes and foreign matter
  • Particulate in the water

To help you better understand how each of these contributes to cloudy spa water, read on for a more detailed explanation.

Filling the hot tub with cloudy water

If you notice your hot tub cloudy and foamy immediately after filling, it could be the source of your water causing cloudy hot tub water. If you’re uncertain of the source of the fill water in your hot tub, it’s a good idea to check where the source water is coming from. You want to make sure you aren’t starting out with cloudy spa water right off the bat. Is the water coming from a nearby lake or well? If so, it might contain tannins or oxidized minerals such as iron oxide that may be producing cloudy spa water.

High pH and alkalinity of the fill water

Another cause is if the water that’s filling your hot tub has high alkalinity or pH readings. If this is the case, the spa water can quickly become cloudy on the initial fill. Balancing the alkalinity and pH will clear the water.

Cloudy Hot Tub Water

Dirty filters or insufficient filtration

The filters in your hot tub are a magnet for grime, debris, minerals, or oils that enter your hot tub water. Although this is their purpose, over time, the buildup of these materials in your filter prevents it from working efficiently. This, in turn, can lead to a cloudy hot tub because debris that’s introduced to the hot tub water cannot be filtered out. When this occurs, the debris remains suspended in the spa water and causes cloudiness.

Another filtration issue is if the spa isn’t scheduled to filter frequently enough. This can prevent debris from being accumulated in the filter promptly, leaving the hot tub cloudy and foamy.

Oxidizing minerals in the water

At the start of the 2016 Summer Olympic Games in Brazil, there was mass panic when their Olympic-sized swimming pools turned a thick green-yellow color. Unfortunately, this does happen and is the result of a chemical reaction between the dissolved minerals, such as iron and copper, in the water, and the addition of chlorine, bromine, or non-chlorine shock. When minerals and chlorine, bromine, or shock are combined, the minerals in the water begin to oxidize, or rust. The result is discolored cloudy hot tub water after shock that often appears green or yellow.

Poor hot tub sanitation

Insufficient sanitizer levels can cause a hot tub that’s cloudy and foamy. When impurities are introduced to the water from bathers, the water source, or other environmental sources, the particles can intensify if sanitizer levels are low. The result is cloudy spa water.

Hot tub contamination

A common theory as to why cloudy hot tub water sometimes turns a green color is because of algae. While it’s just one of a few reasons your water can turn green, it is sometimes the cause. Algae, along with chlorine-resistant bacteria and mold, can often grow in your hot tub and contaminate the water, leaving you with a cloudy hot tub.


Murky and cloudy hot tub water

The removal of accumulated buildup in the plumbing

The buildup of substances such as calcium, lime, and minerals often occurs in the plumbing systems of your hot tub. What’s worse is the plumbing systems are also a magnet for body oils and leftover chemical binders. If you fill your tub up and add a product with descaling properties to the fresh water, it will work its way through the plumbing and clean out the buildup. The downside is that the accumulation that’s removed may impair the water quality causing cloudy water, odors, foaming, and pH travel.

Spa Marvel Cleanser can solve the problem of buildup by deeply penetrating your spa’s plumbing and equipment and removing biofilm, organic, mineral, and chemical contaminants.

Bathing suit dyes and foreign matter

Some other non-primary causes of cloudy spa water are the dyes from bathing suits leaching into the hot tub water and the addition of other foreign substances, such as a cup of coffee, a glass of wine, and leaves from trees. While these problems rarely occur and are unlikely to impact the overall quality of the spa water, it’s a possibility.

Particulate in the water

When particulate in the water is so fine that it passes through the filter media and stays suspended in the water, it can leave you with a hot tub that’s cloudy and foamy. Spa Marvel Water Treatment & Conditioner can help to sequester the particulate by making it stick together and become a more substantial mass. Once it’s sequestered, the larger mass can be entrapped by the filter media, which will improve water clarity.

Chemical free hot tub


Determining the exact cause of cloudy water isn’t always easy because there are many possible causes. So curing cloudy water may require narrowing down the problem. After reviewing the more common causes of cloudy hot tub water, the following solutions can help resolve the cloudy water problem.

Check your spa filter

The buildup of substances in your filters can have adverse effects and produce a cloudy hot tub. It’s essential to check your filter weekly and give it a good rinse plus a thorough cleaning every month. This will help to get rid of unnecessary buildup in your filter and provide a clean filter for your hot tub.

Balance hot tub chemicals

To help offset water pH or alkalinity levels that are either too low or high, use spa products designed to adjust the levels. Look for pH decreaser or increaser or alkalinity reducer or increaser at your local spa dealer.

Also, when calcium levels are higher than 300 parts per million (ppm), you may need to use scale prevention or water-clarifying agents to get hardness down to the recommended level of 175 to 250 ppm. Sometimes special filters may be required as well. If water hardness is too low, this is an easy fix. Just add calcium hardness increaser.

Use a cleanser or de-scaler

To help clear out the accumulation of calcium, lime, and minerals from your plumbing systems, use a cleanser or de-scaler. Spa Marvel Cleanser is a useful option that deeply penetrates your spa’s equipment to remove these contaminants. After using it, immediately drain out the hot tub water to flush out the buildup and start over with a tub of clean water.

Shock your hot tub water

In the case of minerals oxidizing in the hot tub water, you may need to shock your spa. Indeed, you can get cloudy hot tub water after shock, which initially can cause the green-yellow colored water. But shocking it once again should start to normalize the water color.

Drain your hot tub

If your hot tub is still cloudy after these efforts, drain and clean your spa. Then refill it with fresh water. If your hot tub is near due for its quarterly maintenance, you may want to begin with draining before going to the effort of other troubleshooting, as this may resolve the problem.


Cloudy spa water

There are many things you can do to resolve cloudy hot tub water. But, prevention is the best approach. A big part of cloudy spa water prevention is diligence and discipline.

Use clean, filtered water

The first thing you can do to prevent minerals in your water from filling up your hot tub is to use clean and filtered water. To use filtered water, you can purchase and install a hose pre-filter such as Spa Marvel’s X10 Water Filter.

Check and clean filters regularly

Having a clean filter helps keep the water in your hot tub clean and clear. So follow a regular filter maintenance schedule, which includes checking and rinsing your filters weekly, cleaning them thoroughly monthly, and replacing as needed. A filter should get you about a year’s worth of usage. So change your filters every year as an excellent preventative measure. If you notice tears in the filter or the pleats are sticking together, you’ll want to change the filter immediately.

Keep your water chemistry balanced

It’s essential to create a schedule to check that your water chemical levels are balanced. You should monitor pH, alkalinity, calcium, and sanitizer levels regularly. Then adjust them as needed. Being proactive about this and using chemical balancers, such as pH or alkalinity decreasers, can help to prevent cloudy hot tub water from appearing.

Spa Marvel Water Treatment and Conditioner can also help by reducing the amount of chemicals and the frequency of adjusting them, thereby simplifying water chemistry maintenance.

Drain and replace the water

Your hot tub should be drained and cleaned every three months for proper maintenance. This will remove and prevent the buildup of contaminants and algae.

Follow a regular maintenance schedule

“My hot tub is cloudy!”

If you own a hot tub, chances are you’ve probably said this at some point. Fortunately, there’s a remedy for every cause. The challenge more often is in determining the root cause of cloudy spa water. So prevention is imperative to reduce the likelihood of it occurring in the first place.

Regular maintenance of your hot tub is the best way to prevent cloudy hot tub water from ruining your time relaxing in the tub. To learn how to maintain your hot tub properly, review our Comprehensive Guide on How to Maintain a Hot Tub.

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