Most submersible well pumps manufactured prior to 1979 have oil-filled capacitors containing polychlorinated biphenyls (PCBs), which are classified as probable human carcinogens. Many of these pumps are still in operation. Failed seals in aging pumps can cause capacitor oil to enter wells and contaminate drinking water.

Pump manufacturers discontinued the use of PCBs by 1979. We know that instances of well contamination are still being reported to regulatory agencies, but there is little authoritative information about how many PCB-containing pumps may still be in use. A 1986 warning issued by the New York State Health Department placed the number as high as 57,000 in that state.

Preventing PCB Contamination

PCB-containing pumps should be removed from drinking water wells. If you own a submersible pump and suspect that it was manufactured before 1980, contact the distributor to determine its model number and age (If records for your pump are unavailable, it may be necessary to remove and inspect it.) Confer with your pump contractor or check the EPA web site to compare your model against the list of submersible pumps known to contain PCBs: EPA website

If Your Submersible Well Pump Leaks

Because of its low density, oil leaked from a pump capacitor can reside undetected as a floating layer on top of the water column inside a well. Contamination may not be evident until the pump is serviced or replaced. An oily odor or residue in your tap water may indicate a leaking submersible pump. If you suspect such contamination:

• Do not drink the water.


• Contact a plumber or pump installer to remove and inspect the pump and well.


• Test the water for PCBs. Your local health department can recommend qualified laboratories to collect and test a sample. The federal limit for PCBs in drinking water is 0.5 parts per billion (ppb).


• If the water contains PCBs, report the spill to state and local environmental regulatory agencies and notify the pump manufacturer.


• Retain a qualified remediation contractor to clean and flush the contaminated well and plumbing system before installing a replacement pump.


• Resume use of the well when successive rounds of testing show that PCBs are no longer present above 0.5 ppb. If the water quality cannot be restored, PCBs can be removed from drinking water by the use of a granular activated carbon (GAC) filtration system.


• Consult a physician if you are concerned about possible exposure to PCBs.

Restoring a Well Contaminated by PCB Oil

Only a properly trained and equipped contractor with knowledge of pressure system hydraulics should be retained to clean the well and plumbing system. Handling and disposal of contaminated hardware and wastewater are subject to state and federal regulations. Involve state and local regulatory agencies to determine cleanup procedures in your locality. Basic remediation steps are as follows:

• Remove the submersible pump and tubing from the well. Wrap oily parts in polyethylene sheeting and use sorbent pads to prevent oil spillage and drippage.


• Skim and containerize floating oil.


• Pressure wash the well from bottom to top to dislodge oil from interior surfaces.


• Flush the well and entire plumbing system using a surfactant solution. Replace uncleanable hardware if necessary.


• Containerize oil and wash water for off-site disposal (or on-site treatment via carbon filtration.) Discharging waste into a septic system may be impermissible.


• Flush the well and plumbing system with clean water.


• Test samples of well water and tap water for PCBs to confirm that water meets the 0.5 ppb drinking water standard.


• Repeat pressure washing, flushing and testing, if necessary.


• Replace the submersible pump.

Further Resources:

Fitzgerald, C. 1987. PCB Contamination of a Private Water Supply. Water Well Journal, vol. 41, No. 5, pp. 38-41.

New York State Warns of PCB Well Threat. 1986. Ground Water Age vol. 20, No. 8, p. 16.

Swanson,G.J. 1986. PCBs in Well Water. Water Well Journal vol. 40, No. 2, pp. 60-61.

Swanson, G.J. 1994. Contractor Advises: Test for the Presence of PCBs Before Pulling Pump. Water Well Journal, vol. 48, no. 3.

Wisconsin Dept. of Natural Resources. The Potential for Drinking Water Contamination from Submersible Well Pumps. 1992. Bureau of Water Supply Publ-WS-025-92.