Gases in well water can be a risk, says provincial water engineer

Oxygen, carbon dioxide, nitrogen, methane and hydrogen sulphide occur naturally in some aquifers

Gases in well water can be a risk, says provincial water engineer
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Gases in water wells can be a danger on farms and rural properties, says a provincial agricultural water engineer.

Gases can occur naturally in water wells, dissolving in the water while under pressure and then being released when water is pumped out of the well.

“Sometimes people complain about the smell, but the gases you can’t smell may cause the worst problems,” said Shawn Elgert. “Odourless gases include carbon dioxide, methane and nitrogen, and potential dangers may arise from them.”

He says that water wells that “breathe” have been fatal in Alberta.

“On a low-pressure day, gases can come out of the well head that can contain very little oxygen,” he said. “If the well head is inside a pumphouse, in the basement of a house or — even worse — in a pit, the oxygen in that enclosure can be displaced. It only takes a short time for a person in that enclosure to lose consciousness or even die if they breathe in this gas with little oxygen — even less time than if they try to hold their breath.”

Gases can also collect in a basement if the home has an older pressure tank or cistern in the basement that is not vented to the outside.

“However, modern pressure tanks do not have a relief valve, so this problem does not occur with them,” said Elgert.

Another danger is the presence of a combustible gas, such as methane. A strong enough concentration could result in an explosion, said Elgert citing the experience of one well owner.

“He was venting the gas out of a pressure tank inside a pumphouse because he thought the pump was introducing air into the water. He was near the pump when it kicked on, creating a spark that ignited the gas and blew up the pumphouse while he was still inside. He was fortunate it was such a short burn, and he only sustained minor peeling of skin from his face.”

Overpumping the well can make this problem worse especially when the water level is drawn below the top of the slots or holes in the casing where the water enters the well, he added.

“Other problems can occur on a high-pressure day in winter. Air can go down into the well, freezing the pitless adapter and stop the water from pumping. Gases causing spurting from taps and loss of prime of the pump is another problem.”

Elgert offers these suggestions:

  • Wells in pits should only be worked on by someone with confined space entry training. Well drillers use gas meters to determine if there is enough oxygen in the pit before entering. The meters also test for some other gases including combustible ones.
  • Existing wells in pumphouses or unsealed wells in basements should be capped properly and vented safely to the outside. Older-style pressure tanks in basements that can vent off should be vented to the outside.
  • Overpumping the well can intensify the problem. An assessment of the well can be done to determine a system that would reduce overpumping.
  • Collect a sample with an appropriate method and send it to an accredited laboratory for analysis.

For more information, visit ‘Gases in Groundwater’ at

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