Why Does My Tap Water Taste Metallic? In Plain Words

What secondary standards are

EPA has established National Secondary Drinking Water Standards that set non-mandatory water quality standards for 15 contaminants. EPA does not enforce these “secondary maximum contaminant levels” (SMCLs).

They are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. These contaminants are not considered to present a risk to human health at the SMCL.

EPA believes that if these contaminants are present in your water at levels above these standards, the contaminants may cause the water to appear cloudy or colored, or to taste or smell bad. Secondary standards are set to give public water systems some guidance on levels that are below what most people will find to be noticeable.

These contaminants are not health threatening at the SMCL, and EPA says public water systems only need to test for them on a voluntary basis.

Which contaminants EPA links to a metallic taste

EPA’s table of secondary standards lists the noticeable effects above each secondary level. These are the rows in that table that name a metallic or bitter metallic taste:

• Copper — 1.0 mg/L: metallic taste; blue-green staining
• Iron — 0.3 mg/L: rusty color; sediment; metallic taste; reddish or orange staining
• Manganese — 0.05 mg/L: black to brown color; black staining; bitter metallic taste
• Zinc — 5 mg/L: metallic taste
• Corrosivity — non-corrosive: metallic taste; corroded pipes/fixtures staining
• pH — 6.5–8.5: low pH: bitter metallic taste; corrosion. High pH: slippery feel; soda taste; deposits

mg/L is milligrams of substance per liter of water.

EPA groups the problems from secondary contaminants into three categories: aesthetic effects — undesirable tastes or odors; cosmetic effects — effects which do not damage the body but are still undesirable; and technical effects — damage to water equipment or reduced effectiveness of treatment for other contaminants. Taste and odor problems fall under aesthetic effects, and corrosion and staining fall under technical effects.

Where a metallic taste can come from, in EPA’s words

EPA discusses corrosive water under technical effects. It says corrosivity, and staining related to corrosion, not only affect the aesthetic quality of water, but may also have significant economic implications.

EPA says other effects of corrosive water, such as the corrosion of iron and copper, may stain household fixtures and impart objectionable metallic taste and red or blue-green color to the water supply. It also says corrosion of distribution system pipes can reduce water flow.

EPA lists the standards related to corrosion and staining as: Chloride, Copper, Corrosivity, Iron, Manganese, pH, Total Dissolved Solids, Zinc. It lists the standards related to odor and taste as: Chloride, Copper, Foaming Agents, Iron, Manganese, pH, Sulfate, Threshold Odor Number (TON), Total Dissolved Solids, Zinc.

The route EPA gives: your water provider, and testing

If you are concerned about the presence of secondary contaminants in your drinking water supply, EPA suggests these steps:

• First, identify your local public water system. If you pay a water bill, the name, address, and telephone number of your supplier should be on the bill. If you do not pay a water bill, then contact your landlord, building manager, or the local health department — they should know.
• Second, contact your local public water system. Inquire about your supplier’s monitoring for secondary contaminants. Ask for the list of secondary contaminants which are being monitored in your water supply. Does the water being delivered to the public meet these SMCLs? If you have not yet received notice from your supplier, ask how you can get a copy of the monitoring results.
• Third, if you receive a public notice from your local public water system regarding other drinking water standards — read it carefully — and follow any instructions closely. If you have questions or concerns, contact the person from the water system who is indicated in the notice. If that person is unavailable, contact either the state drinking water program or your local health department.
• Fourth, contact your state drinking water program if your water supplier is unable to provide the information you need. Ask if your water supplier is consistently in compliance with both primary and secondary drinking water regulations. Request a copy of monitoring results that were submitted to the state by your supplier.

For a private well, EPA says: if you have a private well and you think that the well may be near a source of contamination or may have been contaminated — have your water tested by a certified laboratory. A list of certified labs is available from your state’s laboratory certification officer.