Teams of water engineers are still battling to return supplies to more than a 1,000 homes in Wales after mains pipes burst.
It followed an around-the-clock fight to reconnect 3,000 properties in the St Clears area of Carmarthenshire on Wednesday and Thursday.
In the latest incident, Dwr Cymru Welsh Water said customers in Rhayader, Powys, lost tap water.
Officials say they hope supplies will be restored on Thursday afternoon.
At 1700 GMT, it said new leaks were causing low pressure in Builth Wells town centre.
"We are locating and fixing these leaks as quickly as we can," said a Dwr Cymru spokesman.
"In addition we have despatched a number of tankers to top up the local reservoir and improve pressure to help supplies return to normal."
The water company said it was dealing with 185 major bursts a day after the thaw in the weather since Boxing Day.
Its operations director, Peter Perry said staff were working "at full stretch" to rectify the supply problems.
In Carmarthenshire, engineers worked through Wednesday night to replace pump equipment serving St Clears.
In total, 3,000 homes were cut off.
"The teams we had on site have worked consecutively now for 36 hours," Mr Perry told BBC Radio Wales.
"In the early hours of this morning the pumping station was brought back into commission and is now putting water back into our Foel service reservoir which supplies the bulk of our customers who were affected.
Earlier on Wednesday, a further 2,000 homes in the Llandrindod Wells area lost supplies, caused by the thaw.
"To put this in perspective, I've been in the business 30 years and I don't think we've ever had a winter like this," added Mr Perry.
"That change in temperatures last week from minus 10 in our rural areas to plus 10 over the past couple of days has seen an unprecedented number of bursts."
Areas still affected stretch from Erwood near Builth Wells in Powys, across to Llanrwst in the Conwy Valley.
Dwr Cymru Welsh Water said it logged between 5,000 and 6,000 calls from customers reporting problems since Boxing Day, compared with 600 on a typical busy day.
It is giving updates via its website to customers whose supplies are affected.