In the summer, homes, and businesses in East Kilbride, Rutherglen, and Hamilton in Scotland experienced discoloration of their tap water.

After investigation, it was found that it had been caused by seasonal manganese levels that were giving the water a brownish tinge, but the water was still safe to drink.

This got us thinking about how different elements can affect water quality. The good news is that Britain’s tap water supply is one of the safest in the world and is regularly tested to ensure it remains safe to drink. Finding discoloured water is a rare occurrence, but it would be useful to know in advance what the cause might be and what actions your business may need to take to fix it.

Dr Alex Murdoch, Technical Relationship Manager at Castle Water, says, "A change in water appearance can be disconcerting, and although most causes may not cause any harm, sudden unexpected changes in colour may indicate an underlying problem which should be investigated. Understanding the different causes should help you identify the issue and take appropriate action."

Here’s our guide to tap water discoloration:

Brown or yellow water

Brown or yellow discoloration could occur because of deposits of manganese or iron, which are naturally occurring minerals. Over time, they’ll settle at the bottom of the water mains and not bother you, but sometimes if there’s a burst pipe or a rush of water, the sediment will be disturbed and will come through the taps. It’s unlikely that the brown water will be harmful, but it is certainly not pleasant and the cause needs to be found and rectified as soon as possible.

Alternatively, if brown water is only coming out through the hot water taps, it could mean you have a problem with corrosion in the hot water system. In which case, you will need to call a plumber.

Blue or green water

If your water looks blue or green, it could be caused by higher than usual levels of copper. This is likely to happen if you have recently had copper pipes fitted and will stop happening after a few days. On the other hand, if your copper pipes are old, the discoloration could be caused by corrosion, in which case you will need to get the pipes replaced.

An alternative reason is that one or more of your toilet cisterns could have been poorly installed allowing the water to drain back into your water supply. If you use a blue or green toilet cleaning tablet that you drop into the tank and your tap water is a similar colour, this will be the reason. Do not use the tap water for drinking until the problem has been fixed by a plumber.

Cloudy, grey or white water

If your tap water is cloudy, the cause will probably be trapped air bubbles. They cause no harm and will gradually disappear. If you fill a glass with water, you’ll notice the water becoming clearer from the bottom upwards. It is likely that the air bubbles were caused by trapped air getting into the water supply if repairs were carried out, so over time the problem will sort itself out.

Bits in the water

Discoloration can be caused by tiny particles such as white limescale, or it can be caused by old washers that are beginning to disintegrate. If old washers are the issue, change them, then run the taps until the water runs clear.

Slime in water

If your water leaves a slimy or mouldy residue on your surfaces, it could be caused by mould spores in the atmosphere. The spores feed on soaps and cleaning products, and they are often found in areas with limescale. The problem is external, and the tap water itself isn’t affected.

If you have a problem with the colour of your water, check with neighbouring businesses to see if they’re having similar issues. If your business premises are the only ones affected, then it will probably be an issue with your piping and the best thing would be to get a plumber to have a look at it.

If you notice discoloration in your tap water, Dr Alex Murdoch advises, "Supply incidents including water quality issues can be reported to your network owner directly; it is their responsibility to ensure the water supplied to your property meets the relevant standards. However, if the issue is within the property boundary, it is the customer’s responsibility to resolve."

You can contact your water network owner directly using the contact details provided here.

Alternatively you can use our live webchat at to report issues with your water supply to one of our advisors.

Don't forget, you can use our free Water Efficiency Guide to start saving water and money in your business. You can find more tools to improve your business water efficiency here. Our professional network or specialist partners can help your business with Additional Water Management Services including Emergency Water Supply and Water Efficiency Audits.

Switch & save up to 20%

We're helping businesses in England & Scotland save on water bills, and with more 5-star Trustpilot reviews than all other water retailers combined - our customers recommend us.

Get a quote