Odor in Well Water

Odors in well water are commonly caused by iron and/or sulfur bacteria or compounds of iron, manganese, and sulfates.

For example, hydrogen sulfide gas (“rotten egg odor”) frequently occurs in well water due to decaying organic matter, the activity of sulfates, and various species of sulfur or iron bacteria.

These bacteria can be removed in a number of ways, but the first, most basic step you can take is to:

1. Check Your Toilet Tank

Unless it is new or has recently been cleaned, your toilet flush tank can offer a wealth of useful water quality information! Simply lift the cover and look in.

If you see slimy rust deposits on the sides of the tank and frothy bubbles in the tank water, this may indicate the presence of iron bacteria. Furry, stringy red or black growths can also indicate the presence of iron or sulfur bacteria, respectively.

2. Check for Odors in Cold & Hot Water

Run a hose bib or tap as close to the well as possible, fill a 5-gallon bucket or another container, and check for odors. If you smell a “rotten egg” odor, this is hydrogen sulfide gas.

If the water smells like oil or asphalt, manganese can be the cause. If it smells like cucumber or sewage, iron and/or sulfur bacteria are usually the cause.

Run hot water from each tap to determine if there is an odor in the hot water that is not in the cold water. If so, this indicates a problem with the water heater.

Iron and sulfur bacteria can interact with the anode rod in water heaters, resulting in hydrogen sulfide gas only in the hot water. Changing the anode rod to an aluminum rod can often solve this problem.

It is recommended that you drain your water heater at least once per year. This will flush out sediment that may accumulate in the bottom and give you an idea of your sediment's type and color, if any is present.

If your toilet tank, water heater, or water tap appear to exhibit symptoms of bacterial contamination, your next plan of action should be to:

3. Test Your Water

well water test kit — Well Water Test Kit

If there is an odor problem with the water supply, the first step is to determine the source. If the source is directly from the well, a general mineral water analysis is critical to selecting the correct system.

At minimum, tests should include analysis for pH, iron, manganese, hardness, total dissolved solids, and oxidation-reduction potential.

Additional tests for sulfate, hydrogen sulfide, and tannin are recommended. Take the sample as close to the well as possible.

With these results, you can identify the best type of water treatment to use and the type of system to select based on your water chemistry. Avoid in-home water testing by water softener salespeople during sales demonstrations.

If your water source is a public system and you experience problems with odor, it is important to contact a utility official to determine whether the odor is from the public system or from your home's plumbing or piping.

Once you've identified the contaminants in your water, the next step is to:

4. Determine Well Water Flow Rate

You'll need to know your well's flow rate before you begin researching water treatment systems, as every system has certain pressure or flow rate requirements. To determine your well's flow rate, grab a 1—or 5-gallon bucket and a watch or clock.

1. Open any hose bib or faucet until pump turns on.
2. Close the hose bib or faucet and let the pump fill up the pressure tank until it turns off.
3. Using a 1 or 5-gallon bucket, open the faucet and collect and measure all water discharged until the pump turns on.
4. When the pump turns on, immediately close the faucet and start the pump cycle.
5. When the pump turns off, record the pump cycle time to refill the pressure tank in seconds.
6. Divide the number of gallons collected in Step 3 by the number of seconds in Step 5.
7. Multiply the answer from Step 6 by 60.
8. The answer in Step 7 is the average pumping capacity of the pump in gallons per minute (GPM).

5. Choose a Disinfection Method

The most common method of killing odor-causing bacteria in water is to inject liquid chlorine into the water as it flows through your pipes.

You might also choose to use a chlorine pellet feeder or even a metering pump with hydrogen peroxide instead of chlorine.

Note that these options generally necessitate the inclusion of a carbon filter to remove trace tastes and odors from chlorine/peroxide and a contact tank to ensure sufficient contact time between the disinfecting solution and bacteria.

Another option is to use ozone injection to kill bacteria and oxidize iron and manganese for filtration.

Or you could use an oxidizing iron filter to oxidize iron and remove hydrogen sulfide gas with one system. These systems use either air, chlorine, hydrogen peroxide, or ozone to oxidize iron and kill bacteria.