South Staffordshire Water said problems were reported in the Dudley, Tividale and Oldbury areas on Sunday afternoon.
It was due to a power failure at one of the company's booster stations, which caused low pressure and loss of water supply to some customers.
A spokesman for South Staffordshire Water said on Sunday afternoon: "We are aware that there is a problem in the Dudley, Tividale and Oldbury area that is causing low pressure and loss of water supply.
"This is due to trip at our booster station ,our engineers are on route to rectify the fault.
"We apologise for any inconvenience caused and thank customers for their patience while we work to resolve this as soon as possible"