It was caused by a power supply problem at a treatment works in Hampton and Ashford which has now been fixed.
50 postcode areas were affected, and some schools had to close.
Thames Water says customers can expect their supply to “take some time” to return – with tankers sent “as a precaution” to some parts.
St Richard Reynolds College in Twickenham posted on social media that it had “no option but to close” due to the water issues.
More information can be found by clicking here ; Thames Water information update.