How Safe is Yellow Tap Water?
Why is my water yellow?
We are fortunate to enjoy some great quality tap water in the UK, but occasionally it may become contaminated. For the most part, water issues are subtle and difficult to detect but every now and again someone in the UK will open their tap and be greeted by a flow of yellow water. We put great trust in our kitchen taps and it can be quite alarming to see anything that doesn’t resemble a pure mountain spring coming from them. So, what’s causing the water to turn yellow and is it dangerous?
Discoloured water can range from a straw yellow colour through to rusty red or brown, and even to black. Whilst water discolouration can be due to a number of issues, if you are on a mains water supply its highly likely that the issue is caused by rusty sediments containing iron and manganese.
Is drinking discoloured water dangerous?
Several of the UK water supply companies describe yellow water as harmless. We know that iron is an essential micronutrient and a lack of it can lead to anaemia, but too much (iron overload or haemochromatosis) is also bad for us. Iron overload can lead to a number of symptoms including: chronic fatigue, weight loss, joint pain, weakness, irregular periods, and erectile dysfunction. Perhaps more concerning is that other (more toxic) metals such as manganese may also be present in rust sediments. We do not recommend drinking or bathing in water that is discoloured with rust.
How does rust get into tap water?
There are two main sources of rust sediments in our drinking water. Firstly, iron and manganese are naturally present in the rocks through which our rainwater and rivers flows. Small quantities of these metals can dissolve into the drinking water which, over time, can combine with other material to form rust sediments in pipes. Secondly, many of the pipes that supply our water are themselves made from iron. Corrosion of iron and galvanised pipes can lead to build up of colloidal suspensions and deposits of rusty sediments.
Rust sediments that have built up in pipework may suddenly become a problem that leads to discoloured water when they become disturbed, this can be due to a number of reasons including:
- Maintenance activity, flushing
- Corroded water company pipes
- Burst pipe
- Corroded household plumbing
- Activity of the Fire Service
Pipe maintenance - flushing
To keep your water main in good working order your water company may periodically undertake maintenance work. Valves are opened wide and water is flushed through at high speed. The flushing procedure is designed to stir up and remove any iron and manganese sediments that my have accumulated in the pipes. Maintenance is often conducted overnight when pressure drops cause less inconvenience, so if your tap water discolours overnight this is probably the issue.
Over time the action of the water on iron mains pipes used in the water distribution network can lead to corrosion. Rusty iron and manganese deposits from the corroded pipes can lead to discoloration of your tap water. Unlike pipe maintenance activity, which tends to cause very sudden changes in water colour, water from corroded pipes may have a very slight yellow colour and be difficult to detect.
Occasionally you may experience burst pipes due to physical damage or corrosion, this can lead to sudden changes in water colour and may be associated with a drop in water pressure. Leaks in pipework may occur in the supply pipes to your property (water company’s responsibility) or in the supply pipes that run through your property (home owner's responsibility).
Corroded household plumbing
If you regularly experience discoloured water that runs clear after a couple of minutes then the chances are that the problem is due to corroded pipes or fittings in your household plumbing. Similarly, if you only experience discoloured water from certain taps then this is unlikely to be a problem with your water supply.
Activities of the fire service
Very occasionally your fire service may need to access water from a hydrant in the street. Emergency services drawing large amounts of water can lead to pressure changes in the system that can stir up sediments and lead to discolouration in water supplies.
What should I do if my water suddenly turns yellow?
A good starting point would be to speak to your neighbours and find out if they are similarly affected. If none of your neighbours is affected then there’s a good chance that the problem is either in your plumbing or in the pipes that connect your property to the mains.
If your neighbours are similarly affected then a call to your water supply company should be your next action. The water company should be able to identify if there is scheduled maintenance activity that might affect your supply and will be able to further investigate the issue. If you are unsure who supplies your water you can check with Water UK.
If your water has suddenly turned yellow then you will want to run a tap until it turns clear. Preferably use the tap that is closest to where you connect to the water supply. Depending on the severity of the problem you may need to run the tap for up to thirty minutes for it to run clear. If you are on a metered water supply we recommend you contact your supply company to ensure you are not charged. There are some things you will want to avoid until your water supply returns to normal.
Things to avoid
- Drinking & Bathing
- Using hot water
- Using a dishwater or washing machine
- Water heater & electric showers
- Use of water softener
Drinking and bathing
It probably goes without saying that you should avoid drinking or bathing in water that is discoloured. As the discolouration is caused by iron and manganese contamination, boiling the water will not make it safe to drink. Refrain from using your water supply and drink bottled water until the issue has been fixed.
Using hot water
If your water has discoloured suddenly then the problem will be likely be contained to your cold-water supply. Whilst your hot water taps may well run clear the hot water system will be topped up from your cold-water supply. Running your hot taps will result in contaminated yellow water being drawn into your hot water supply and is best avoided.
Using dishwashers and washing machines
As you want to avoid drinking and bathing in contaminated water you will also want to avoid washing your dishes in it! The rusty water is also likely to stain clothes so avoid using these kitchen appliances until your water supply has returned to normal.
Water heaters & electric showers
Using water heating appliances such as electric showers whilst you have discoloured water may lead to deposition of sediments in the appliances leading to loss of efficiency or appliance failure, we recommend you avoid using these appliances until your supply problems are fixed.
Water softeners reduce the hardness of your water by removing calcium and magnesium ions. If you have a softener installed then you will want to avoid using your softened water taps which, in turn, will limit discoloured water being drawn into your softener and contaminating the ion exchange resin.
Do I need a water filter?
If your water has suddenly change colour then it’s likely that the problem will be short lived and will return to normal quickly. If you’ve had discoloured water for a longer time but it’s only a problem in certain taps then a visit from a plumber might well be a good investment. However, if you’ve had a long term problem with water colour and investigations with your water supply company have not found a solution then you may want to consider filtering your drinking water. Reverse osmosis or activated carbon filters will effectively remove discolouration from water. Before purchasing water filter equipment we recommend that you have your water professionally tested in a laboratory.
The bottom line
Seeing yellow, brown or black water flowing from your drinking taps can be alarming but it’s unlikely to be a long-term problem. Avoid using your water supply until the problem has been properly resolved and contact your water supply company for advice if you are concerned.
Whilst a sudden and dramatic change in your water colour is likely to be due to a specific and temporary cause you may wish to have your water tested in a laboratory to check for iron, manganese or other common contaminants.