Around 150 homes south of Draperstown are still without water according to NI Water, but homes in Cookstown and Pomeroy are believed to have seen their services return to normal.
A spokesperson for the company said: “There is an ongoing issue in an area to the south of Draperstown affecting water supplies to approximately 150 properties.
“NI Water has multiple staff deployed in the area to address air locking in the system and we are hoping to have this resolved later today.
“Alternative water supplies are being made available to affected customers.
“NI Water fully recognises this is a frustrating experience for our customers, and can assure them we are doing everything possible to restore water supplies as quickly as possible.
“We would like to once again thank our customers for their continued patience whilst this problem is being resolved.”
The problems started in Cookstown on Monday when residents in homes and farms serviced by the Water Treatment Works at Lough Fea reported having no water.
The affected 35 homes in Pomeroy are believed to suffered disruption to their supply on Thursday, along with those in Draperstown.
NI Water said Cookstown and Pomeroy lost their water supplies as direct result of industrial action, whilst homes in Draperstown are suffering disruption due to an electrical supply issue caused by bad weather.
“NI Water is dealing with an electrical supply issue caused by the current weather situation at Mormeal Service Reservoir which supplies customers in the Draperstown area,” they said on Thursday.