Discoloration, sediment and other particles in drinking water

DISCOLORATION AND SEDIMENT SOURCES

On rare occasions, tap water may become discolored or you may notice sediments. The discoloration can range from cloudy to light yellow to dark brown color. At times, customers have reported noticing black or white particles.

TYPES OF DISCOLORATION

Cloudy or Milky

Milky or cloudy water is often caused by air bubbles in the water system. Cloudiness and air bubbles do not present a health risk. Typically air enters the distribution system because of  changes in the water temperature or during construction/repairs. If you notice cloudy water, fill a glass with tap water and let it sit for a few minutes. The cloudiness and air bubbles should naturally disappear. Flushing your cold water tap for 5-10 minutes should clear up the cloudy water. If the cloudy water does not disappear after 10 minutes of flushing, please contact our Water Treatment Plant Laboratory staff at 919-537-4228 or wtplaboratory@owasa.org

Yellow to Dark Brown

Water heaters are a common source of yellow or brown discolored water.  If the discoloration is only in the hot water, accumulated sediments in the bottom of the hot water tank are likely the source.  We recommend flushing water heaters annually following the manufacturer’s instructions or contacting a licensed plumber for advice.

If your water is yellow or brown or rusty in color, the cause is likely iron or manganese sediments that have settled in the water pipes over time.  Iron and manganese are both naturally present in our reservoirs. In addition, iron pipes in our distribution system can be a source of iron discoloration. Maintenance and repair work, nearby construction, or flushing of water pipes (by releasing water from a hydrant or other release point) may stir up these particles and cause discoloration. Iron and manganese in drinking water are not a health risk.

Discoloration is usually temporary and should disappear after water is flushed from the distribution system or your home plumbing. OWASA recommends not drinking tap water if it is discolored. In addition, do not wash clothes when water appears rusty, because the rust can stain fabric. Flushing your cold water tap for 5-10 minutes should clear up discolored water. If the color does not disappear after 10 minutes of flushing, please contact our Water Treatment Plant Laboratory staff at 919-537-4228 or wtplaboratory@owasa.org

Green/Blue

If your water is green or greenish blue in color, this may indicate deterioration of copper plumbing (e.g., in a water fountain). OWASA recommends consulting with a plumber to find the source of deterioration and a possible solution.  

The Laboratory staff at our Jones Ferry Road Water Treatment Plant.

Left to right: Robert Herring; Katie Harrold, Supervisor; Chris Gibbons. 

Black Sediment or Particles

Black particles are often precipitated iron and manganese in water.  Iron and manganese are both naturally present in our reservoirs. In addition, iron pipes in our distribution system can be a source of these particles.  Maintenance and repair work, nearby construction, or flushing of water pipes (by releasing water from a hydrant or other release point) may stir up these particles. Iron and manganese in drinking water are not a health risk.

Another common cause of black particles in tap water is the disintegration of rubber materials used in plumbing systems. Sources of the rubber materials are typically:

  • toilet flappers,
  • rubber washers/o-rings,
  • membranes in thermal expansion tanks on hot water heaters, and
  • liners disintegrating from the inside of flexible hoses which could be on water heaters or underneath sinks.

In addition, the use of chloramines as a disinfectant can contribute to the disintegration of rubber materials. OWASA recommends replacing the deteriorating rubber (such as a toilet flapper) with one that is resistant to chloramines (which should be clearly advertised on the label).

White Particles

White particle buildup comes from a variety of sources and is most commonly originating from the hot water system. Typically, this buildup is either calcium carbonate or from a type of brass corrosion called dezincification (more information is below).

Dissolved calcium is naturally found in our drinking water and can change to calcium carbonate in hot water heaters. Over time, calcium carbonate may accumulate at the bottom of the hot water heater and collect in your faucet aerators. OWASA recommends periodically flushing your hot water heater to remove any sediment buildup.

DEZINCIFICATION OF BRASS 

Dezincification is an electrochemical process in which zinc, a component of brass, is released from low quality brass fittings. When zinc is released from brass, it often forms zinc oxide, which may be visible as white or gray sediment in a plumbing component. This sediment may slow or block the flow of water.  The loss of zinc may also weaken the brass fitting or result in leaks.

Recirculating hot water heater systems may be susceptible to brass dezincification because hot water is continuously in contact with the plumbing components, and heat accelerates the buildup of zinc oxide (white or gray sediment). OWASA recommends that you get specific advice from a licensed plumber based on the type of heating/plumbing equipment you have.

Under current national codes, brass fittings in plumbing equipment are required to have a low level of zinc to limit the potential for dezincification. Fittings made with dezincification resistant (DZR) brass are available.

The direct connection of dissimilar metals (e.g., brass and steel or brass and copper) can accelerate dezincification.  Plumbers use fittings called dielectric unions to separate dissimilar metals and minimize the potential for galvanic corrosion.

Black/Grey or Pink/Orange Slime

Bacteria, mold and fungi can grow on surfaces where water is exposed to air (e.g., in a toilet bowl, around sinks or in showers). They may appear black or pink in color.  These growths are produced by airborne fungal spores or bacteria and are not originated from drinking water. OWASA recommends periodically scrubbing and cleaning the toilet, shower, or sink with cleaning products containing bleach.

For concise information on taste, odor, color and sediment in water, please click here.

FOR MORE INFORMATION

Which water pipes are OWASA’s, and which are privately owned and maintained?

Which sewer pipes are OWASA’s, and which are privately owned?

Water expands due to normal operation of a water heater, and what to do about this

What is a p-trap?

Protecting pipes from freezing

Water pressure in plumbing systems; pressure reducing valves

Having a water shut-off valve and marking its location(s) in your plumbing system