Stagnant Water: Why It’s Dangerous and How to Get Rid of it

By: Diana Rodriguez-Zaba
Updated on: March 25, 2024

Homeowners know how important it is to keep the house and yard in top shape. Commercial property owners and managers recognize how building upkeep impacts customers and tenants. Stagnant water is an easily overlooked nuisance that can create all kinds of problems at your home or business.

By the time you notice the foul smell, stagnant water is already seeping into your house or building. It quickly begins breeding microorganisms that cause serious illnesses. As Chicago’s leading water damage restoration company, we understand the structural risks and the threats to your health.

This guide outlines what causes stagnant water, why it’s so dangerous and how to clean it up. We also offer tips on preventing standing water inside and out.

What Is Stagnant Water?

Stagnant water forms when there is no longer a natural or mechanically generated current. It can happen in a park pond or a flooded home basement. It can occur in the plumbing network of a commercial building or manufacturing site. There isn’t a definitive measure for standing water.

category 3 stagnant water
Stagnant water in a bathroom due to category 3 flood damage

Mosquitoes breed in less than one-quarter inch of water in the yard. The potential for stagnant water in a hotel swimming pool can top 20,000 gallons. Depending on the water’s volume and environment, a backyard puddle can become stagnant overnight. It might be two or three days before the pool turns green and begins to smell.

The source of standing water is also a critical factor. Storm flooding, heavy snowmelts and sewage backups leave behind dangerous stagnant water. Classified as Category 3, these types of black water can easily contaminate plumbing and water distribution systems in homes and commercial properties.

How Does Water Become Stagnant?

There are many situations that interrupt water flow and result in stagnation. The problem impacts plumbing systems in both residential and commercial buildings. These are the three most common sources of stagnant water.

plumbing leak leading to standing water
Plumbing leaks can lead to the formation of stagnant water

1. Clean Sources

Water released through a slow plumbing leak or sudden pipe burst is usually Category 1 clean water. Left unattended, it quickly becomes stagnant. Rain dripping through the roof or around windows is initially classified as clean, but it becomes Category 2 as the water becomes stagnant in surrounding materials.

2. Contaminated Sources

Stagnant water classified as Category 2 gray water originates from contaminated sources. This type of water often results from dishwasher or washing machine leaks, broken sump pumps and interior wall leaks in basements.

3. Emergency Sources

Emergency conditions can flood a property with Category 3 black water or affect clean, external water supplies. It usually impacts multiple properties. The residual stagnant water quickly becomes a dangerous source of bacteria, parasites and chemicals.

It’s important to note that commercial buildings deal with unique sources of stagnant water. These are a few examples.

  • Long-term shutdowns caused by natural or structural emergencies
  • Low water usage due to building-wide vacancies
  • Reduced usage during seasonal slowdowns
  • Equipment failure in water towers and supply lines

The Dangers of Stagnant Water

Stagnant water attracts rodents and insects. As it soaks into a building’s structure, it damages wood, drywall and concrete. The odor spreads from floor to ceiling. Stagnant water also hosts dangerous microbial pathogens.

  • Bacteria including salmonella, staphylococcus and E. coli
  • Viruses such as Norwalk virus, hepatitis E. and rotavirus
  • Parasites such as cryptosporidium, E. histolytica and giardia
  • Unhealthy mycotoxins released by toxic black mold fungus

Stagnant water has the potential to transmit diseases through residential and commercial plumbing systems. In homes, it can affect water faucets, dishwashers and washing machines.

In commercial settings, contaminated water impacts point-of-use equipment. It causes bacterial biofilm to grow inside ice machines, drinking fountains and water faucets. This type of plumbing pathogen spreads quickly through a building. It’s very difficult to remediate.

How to Get Rid of Stagnant Water

It’s important to take care of stagnant water as soon as possible. Start by addressing the water source. If needed, call in water damage technicians who handle plumbing leak repairs. Follow these six steps to get rid of stagnant water.

Professional water damage restoration equipment is critical in addressing stagnant water

1. Rent the Right Equipment

Keep the job manageable by renting water removal and drying equipment. Most home improvement stores lease submersible pumps, wet vacs, heavy-duty fans and dehumidifiers.

2. Remove Stagnant Water

First, pump out deep pools of standing water. Follow up with a wet vac to remove as much remaining water as possible. Finally, mop soaked floors, and wipe down wet walls with old towels.

3. Tear Out Damaged Materials

Don’t try to save soggy drywall, baseboards and carpets. The damaged materials are breeding grounds for mold and mildew. Remove everything affected by standing water. Be sure to extend tear-out zones well beyond wet areas.

4. Start the Drying Process

Position heavy-duty fans so that they circulate fresh air crosscurrents over damp surfaces. Run dehumidifiers and air-moving equipment 24/7. The drying process can take from three days to a week or more.

5. Clean and Disinfect

Clean all affected materials. Mix up a disinfecting solution with 1 cup of bleach and 1 gallon of water. Use it on non-porous surfaces to kill mold and bacteria. Sanitize porous materials with antibacterial spray products.

6. Replace and Restore

Give the area a few more days to completely dry. As you replace damaged materials, keep an eye out for residual moisture and mold. Eliminate foul odors and restore interior air quality by renting a HEPA-filtered air scrubber.

Power Tip: If you’re dealing with stagnant water left behind by storm flooding or sewage contamination, don’t try to clean it up yourself. Both are classified as Category 3 black water. Call in a certified water damage contractor who specializes in this type of hazardous cleanup.

Stagnant Water in Commercial Buildings

Once it’s been contaminated, a commercial building’s water supply system needs professional remediation. The extra measures are especially important after storm flooding or sewage backup.

You might need to flush the entire distribution system including point-of-use equipment and end-of-pipe devices. Water filtration and softener systems may also need replacing, especially individual filters at drinking fountains and hand washing stations. Bring in a licensed HVAC contractor to confirm the integrity of heating and cooling systems.

Consult with certified water damage specialists who know how to treat stagnant water in commercial buildings. They can develop an action plan specific to your property so that you can reopen for business quickly and safely.

Stagnant Water vs. Running Water in Commercial Buildings

Preventing stagnant water in commercial buildings involves additional challenges. These large systems constantly circulate water through an intricate plumbing network. Equipment failure anywhere within the system can compromise fresh water throughout the entire property.

Performance, temperature and humidity controls should be closely monitored on chillers, cooling towers and heat exchangers. Make sure supply lines for all point-of-use stations are inspected on a regular basis.

Routine system maintenance is crucial to minimizing the risk of stagnant water contamination in commercial buildings. Work with facility managers to develop inspection schedules specific to monitoring your property’s water supply.

How to Prevent Stagnant Water

stagnant water

Hidden leaks and plumbing problems happen in every home and business. It’s impossible to stop storms from leaving puddles in the yard. Still, you can minimize the chances of water standing and becoming stagnant inside and out.

• Routinely check plumbing for signs of trouble.

• Make sure shingles and gutters stay in good shape.

• Inspect weather seals around doors and windows.

• Eliminate low spots in back and front yards.

• Grade soil to drain away from your property’s foundation.

Dealing with Stagnant Water at Your Chicago Home or Business? We Can Help

It’s not always as simple as mopping the basement or waiting for the sun to dry up backyard puddles. Stagnant water can affect your health and your property’s structural integrity.

We specialize in all types of water removal including sewage cleanup and biohazard cleanup. When you’re dealing with stagnant water, you want Chicago’s most trusted water damage restoration services.

You need our teams here at ServiceMaster Restoration by Zaba. We’re always ready for your call: 773-647-1985

How long does it take for water to become stagnant?

It depends on water location, temperature and surrounding conditions. Standing water can support insects, bacteria and mold growth in as little as 24 hours.

Is it possible to sterilize stagnant water?

Yes, but it’s only recommended in emergencies. The EPA provides instructions for disinfecting drinking water in situations where bottled water isn’t available.

What does it cost to clean up stagnant water?

The cost of stagnant water cleanup and remediation is similar to Category 3 water cleanup averaging $7 per square foot. Final cost depends on the size of affected areas and extent of damage.