Why does my water smell musty?

21/03/2017 Océane Bidault

If your water smells musty, earthy, even slightly fishy, it is likely the result of an environmental factor but shouldn’t be cause for concern. Algae, bacteria and other organic matter can make their way into the water supply and cause a strange odour, but they are typically not harmful. Similarly, a build-up of naturally-occurring metals – like iron and copper – can produce an undesirable smell but these are equally non-threatening in low quantities.

On a rare occasion, however, a musty smell can indicate contamination. Therefore, it is important you identify the source of the smell to confirm you are not at risk.

What causes my water to smell musty?

Musty-smelling water occurs for several reasons. A common cause is from decaying organic material that has found its way into your pipework from the water’s source, releasing the earthy aromas when you turn on the tap.

If your supply comes from an open body of water—such as a river—naturally-occurring organic matter often leaves a residual earthy aroma in the treated supply, which can be more pronounced in summer but is entirely harmless.

The smell can also stem from eroding pipes, or sedimentation, that introduce trace levels of copper, iron and lead into your water supply, altering both its smell and taste but causing no ill-effects.

While none of the above is harmful, if the odour takes on a more pungent whiff of rotten eggs, this could indicate elevated levels of sulphur in the water. In such a case, we recommend you seek immediate advice as strong, foul smells highlight the risk of more serious pollutants in your water supply.

What should I do if my water smells musty?

A musty smell shouldn’t be cause for concern, but it can be unpleasant. So to fix the problem, your first step is to identify the source.

Fill a glass with cold water and step away from the sink before you smell it. If the water appears clean, but the sink smells earthy, then the issue may be in your sink trap or u-bend—clean the tap and drains, and this should solve the problem.

If the water in your glass smells, then there is an issue with your supply. If the odour is worse in the morning, or when you have been away from home, it is likely due to harmless microbes that grow when water isn’t used for an extended period or is slow-flowing.

In this instance, you may need to fix something in your pipework. Alternatively, you could purchase a carbon filter that removes any organic matter suspended in your water. The filter should stop the unpleasant aroma and return your water supply to its desired taste.

If running your water doesn’t remove the smell, ask your neighbours if they’re suffering from the same problem. If yes, there is an issue with your water supplier. If you live in a rural area, it could be localised and simply require that your water supplier flushes the local network around where you live.

In more densely populated neighbourhoods, the issue is likely more severe, and the UK Drinking Water Inspectorate recommends you contact your supplier immediately, detailing:

• When you noticed the smell for the first time?
• What are the characteristics and strength of the odour?
• How many neighbours are experiencing the same problem?

You will find an emergency contact number either on your water bill or on your water supplier’s website. If your water supplier fails to fix the problem, you can contact the Consumer Council for Water, which is the independent body for the water industry for England and Wales.