Water that smells like rotten eggs typically results from elevated levels of sulphur bacteria or hydrogen sulphide gas in your water supply. If you fill a glass with cold water, step away from your sink and smell, a pungent aroma of rotten eggs indicates this is the case. In most cases, the water is perfectly safe to drink. Although a sulphurous stench can indicate hazardous contamination in which case you case you should seek expert advice from your water provider. If the smell only comes from your hot water supply, the issue is likely localised to your water heater.
What causes my water to smell like rotten eggs?
Tap water can often smell musty, earthy, even sewage-like, though this normally results from a simple build-up of organic matter in your plumbing and often, is nothing to worry about. Equally, depending on where you’re located, suppliers routinely add up to five chemicals to the source to ensure your water supply is safe to drink. These include liquefied chlorine, fluorosilicic acid, aluminium sulphate, calcium hydroxide and sodium silicofluoride, which can produce the strange odour.
If your water smells like rotten eggs, there may be an excess level of hydrogen sulphide or sulphur bacteria in your water supply which, in most cases, does not indicate any threat to health. The stench can result from pollution to indicate your water supply is contaminated, and exposure to high levels of hydrogen sulphide can cause skin discolouration, irritation and itchiness, among other symptoms.
Hydrogen sulphide is also a corrosive, and it could damage the metal piping in your house.
What should I do if my water smells like rotten eggs?
Your first action if you smell a strange odour in your water supply is to identify where it’s coming from. A smell of rotten eggs usually indicates a build-up of hydrogen sulphide or hydrogen bacteria, which can come from several sources.
When organic matter such as food, soap and waste, get stuck in your drains, an anaerobic reaction releases hydrogen sulphide, which sinks to the bottom of your pipes as it’s denser than air. When you turn on your tap, the water flow can force the gas back into your sink and cause the sulphurous odour.
To confirm this is not the case, fill a glass with cold water, step away from your sink and smell it. If the water smells clean, but your sink is odorous, you have an issue with the pipework, and you need to clean it. If your cold water is clean and the sink doesn’t smell, but your hot water is overpowering, the problem could be bacteria in your water heater. So, contact a boiler specialist.
If the water is pungent from both your hot and cold taps, the issue could be that your supply is contaminated. Run your tap for a period to see if the smell diminishes, which would indicate the issue is localised and unlikely to be a health risk—using a carbon filter to remove organic contaminants should return the fresh taste and smell.
If the smell remains strong, this would suggest a more widespread concern. Check that your neighbours are experiencing the same smell and, if so, the UK Drinking Water Inspectorate recommends you contact your supplier immediately via the emergency number you see on your water bill or your water supplier’s website.
Your supplier should ask for a sample—or organise local testing—to identify the source of the problem. However, if you are unsatisfied with their actions, contact the Consumer Council for Water – an independent body that monitors the water industry across England and Wales.