How Do I Remove Scum Buildup in My Pool?

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What Is Pool Scum and Why Does It Happen?

Scum buildup in pools usually appears as a sticky, greasy line along the waterline. It can also show up as dull, filmy patches on the surface or pool walls. This residue often results from a combination of oils, sunscreen, lotions, sweat, hair products, and even environmental debris like pollen and dust.

Pool scum thrives in warm temperatures, especially when swimmer load is high and filtration is weak. Scum is more than just cosmetic. Over time, it interferes with chlorine performance, stains the pool, and clogs filters. If left untreated, it can even trigger algae blooms and water cloudiness.

Signs of Scum Buildup in Your Pool

• A dark or greasy line along the tile or vinyl at the waterline

• A slick or filmy feel on the surface of the water

• Foamy bubbles that linger after swimmers leave

• Cloudy water that doesn't clear up with filtration alone

• Reduced water flow or clogged skimmer baskets

• Increase in chlorine usage without explanation

If you start noticing any of these signs, scum may be silently reducing the effectiveness of your entire sanitation system.

Common Causes of Scum in Pools

Several everyday activities and materials contribute to scum buildup:

• Sunscreen and body lotion

• Hair products and makeup

• Natural body oils and sweat

• Organic contaminants like leaves or pollen

• Detergents from improperly rinsed swimwear

• Insects, bird droppings, and other organic waste

A pool party, storm, or consecutive hot days can accelerate buildup. Understanding the sources helps you minimize what enters the water.

Tools and Products You’ll Need

Having the right tools makes cleaning more effective and prevents damage:

• Pool scum sponge or oil-absorbing sponge

• Enzyme-based pool surface cleaner

• Tile and vinyl surface brush or non-abrasive pad

• Skimmer net and skimmer basket inserts

• Manual or robotic pool vacuum

• Test kit for pH, chlorine, total dissolved solids (TDS), and phosphates

• Bucket, sponge, and soft towel for targeted cleaning

Step-by-Step: How to Remove Scum Buildup

1. Skim and Clean the Surface

Start by removing visible debris and film:

• Use a skimmer net to remove leaves, insects, and surface foam

• Empty skimmer and pump baskets to ensure good flow

• Run the pump for at least 6 to 8 hours to circulate water fully

2. Brush the Waterline and Pool Walls

Scum builds up most at the waterline, where oils and dirt accumulate:

• Use a soft-bristle brush or tile brush for stubborn stains

• Scrub in circular or vertical motions to loosen buildup

• Apply a mild surface cleaner or 50/50 vinegar and water solution

• Rinse brush and repeat in small sections

Avoid using abrasive materials on vinyl or fiberglass as it may cause scratching.

3. Add an Enzyme Cleaner

Enzyme-based cleaners break down and digest organic waste, making them ideal for scum:

• Pour in recommended dose while pump is running

• Allow to circulate for 24 to 48 hours

• These also reduce the workload on chlorine and improve water clarity

Enzymes are especially useful after heavy use or frequent sunscreen contamination.

4. Use a Scum Sponge or Oil Absorber

These sponges float on the water’s surface and absorb oils and lotions:

• Place in the skimmer or let it float freely in the pool

• Replace every few weeks or when it starts to look saturated

• Use multiple sponges for large pools or high swimmer loads

Some oil absorbers are washable and reusable, saving money long term.

5. Check and Adjust Water Chemistry

Unbalanced water makes it easier for scum to form and stick:

• pH: 7.2 to 7.6

• Alkalinity: 80 to 120 ppm

• Free chlorine: 1 to 3 ppm

• TDS: under 1,500 ppm recommended

High TDS (total dissolved solids) indicates excessive buildup of unwanted materials. Consider partial draining if TDS is high.

6. Clean or Backwash the Filter

Scum and oils clog filters quickly, especially after treatment:

• Backwash sand or DE filters once pressure rises 8 to 10 psi above normal

• Hose down and chemically clean cartridge filters

• Replace filters annually or as recommended

A dirty filter not only reduces circulation but can reintroduce contaminants into the water.

7. Shock the Pool if Needed

If scum is persistent or water smells bad:

• Use non-stabilized chlorine shock (calcium hypochlorite or sodium hypochlorite)

• Shock in the evening when sunlight won’t burn off chlorine

• Let pump run overnight

• Brush walls and vacuum the floor the next day

You may need to repeat shock treatment twice during peak season.

Prevention Tips to Keep Scum from Coming Back

1. Swimmer Hygiene:

   • Encourage rinsing off before entering

   • Avoid applying lotions and hair products right before swimming

2. Routine Maintenance:

   • Skim daily, brush weekly

   • Vacuum once or twice a week

3. Chemical Balance:

   • Test water 2 to 3 times per week during summer

   • Add enzyme cleaner weekly as a preventive step

4. Use Pool Accessories Wisely:

   • Replace scum sponges regularly

   • Clean toys and floats before putting them in the pool

5. Circulation and Filtration:

   • Run your pump 8 to 12 hours daily

   • Check return jets to ensure proper water movement

Advanced Options for Severe or Recurring Scum

• Phosphate Removers: Useful if you have recurring algae and scum

• UV or Ozone Systems: Help oxidize organics and reduce chlorine demand

• Scum Line Erasers: Specialized scrubbers for heavy stains

• Foam Reducers: Temporary solution to surface foam caused by body oils

If scum keeps returning even after cleaning and adjustments, have your pool water professionally tested for hidden contaminants or systemic issues.

Extra Tips for Saltwater Pools

Saltwater systems can experience scum from similar sources:

• Keep salt cell clean and free of scale

• Balance pH more often as salt systems tend to raise it

• Enzyme products safe for saltwater can reduce buildup

Because saltwater pools operate differently, they benefit even more from preventative enzyme use and consistent brushing.

Keep Your Pool Clear, Comfortable, and Scum-Free

Scum buildup is a common but manageable pool issue. With the right combination of physical cleaning, chemical treatment, and consistent maintenance, you can keep your water clear and inviting. When cleaning becomes part of your routine, scum stays out of the picture and your pool stays ready for swimming every day.