The purpose of this document is to identify possible explanations for fine white air bubbles that are sometimes seen in drinking water immediately after the water is taken from a faucet. These air bubbles disappear within approximately one minute after the water is drawn from the tap.

DES does not believe that there is a health significance to these air bubbles. They may, however, indicate improper physical conditions in pumps, pipes, or other equipment. There are numerous possible explanations for these bubbles. Some are given below.

DISSOLVED GASES
A variety of natural processes take place underground which produce dissolved gas in groundwater. Some examples include:

• radon is produced from radionuclide decay of uranium in bedrock, and
• carbon dioxide and hydrogen sulfide generated from:
1. the decomposition of dissolved organic matter in groundwater, or
2. the by-products of chemical reactions of various naturally occurring mineral deposits.

1. In bedrock (artesian or drilled) wells the water pressure at the bottom of the well is high. At greater depths, a higher level of some gases can be dissolved in the water. When this water is raised by the pump and released from a faucet, these gases may spontaneously come out of solution causing fine bubbles.
2. Water temperature can also play a roll in the amount of dissolved gas that water can hold. As general rule, the lower the temperature of water, the more dissolved gas can be held. When the temperature of the water increases (as happens in household plumbing and in the water storage tanks), these gases may spontaneously come out of solution producing fine bubbles.

INADEQUATE SOURCE YIELD OR OVERSIZED WELL PUMP
The level of water in a well will "drawdown" when the well pump is running. If the drawdown is excessive, air may enter the pump intake. Excessive drawdown can occur if the capacity of the pump is too large for the well's safe yield or if a drought condition has substantially lowered the groundwater table.

This problem can be reduced, in the short run, by using less water. A drawdown "cutoff" device might also be installed to control over-pumping. If drawdown is excessive, damage to the electric motor may occur due to over-heating. Immediate corrective action is appropriate to prevent motor damage.

OTHER MECHANICAL CAUSES
Corrective action is necessary in all of these alternatives below.

Venturi Air Injectors
Certain water treatment systems (typically those used for iron, manganese and odor removal) have a special nozzle that is used to inject air into the raw water. The water is then routed through a tank to provide "reaction" time prior to filtration and to allow excess "air" to be removed.

Check the slope on the plumbing to insure that excess air can reach the air relief valve. Also insure that the size of the aeration nozzle is proper for the amount of water being discharged by the pump. Try reducing the air-to-water ratio produced by the nozzle until just short of the condition when the iron/ manganese or odor treatment device begins to be negatively affected.

Pump Selection
Cavitation is the technical name given to a condition where a severe vacuum forms inside water pump. This often occurs near the pump impellers and is caused by an inappropriate sizing of the pump. When this occurs, dissolved gasses will often come out of solution at the point of maximum vacuum. This can cause severe and damaging loads to the pump. The pump should be resized.

Drain-back Systems
Older water systems, without an air compressor or captive air pressure tank, often have an automatic method for replacing the air "head" in older pressure tank. This plumbing arrangement has a vacuum breaker near the tank and a "bleed" installed on the discharge line inside the well casing.

It is unlikely that this situation would produce fine air bubbles. However, if your well has this configuration please check the amount of air added at each pump start/stop cycle and ensure that the air release valve is functioning.

Faucet Design
The design of certain water use fixture creates great turbulence as the water comes from the faucet. Try another faucet in your home to see if the air bubble condition is the same. If similar, the origin of the bubbles is likely not in the faucets.