Ian Limb of Portsmouth Water said: 'Bursts have always been a risk when there are sudden rises in temperature which causes ground movements regardless whether they are plastic or cast iron pipes.
Water supply is also affected in postcode areas NW5, NW11, N2, N6 and N10.
Companies handed out bottled water to affected customers over the weekend.
"Where possible, take short showers rather than baths, do not leave taps running unnecessarily and only run washing machines and dish washers when you have a full load", the company stated on its website.
South London resident Natasha Prayag told Sky News she was without water late into Sunday night, after her supply was cut off on Saturday evening.
As the company apologised to customers, a spokeswoman said that they were ready and prepared for the thaw but that they were dealing with an "unprecedented number of leaks", particularly around Birmingham.
After Storm Emma, around 12,000 homes are now without water access or are experiencing very low-pressure levels in London alone, according to data released by Thames Water.
If any elderly, disabled or families need help carrying the water, plz let me know.
The cold snap and subsequent thaw has put extreme pressure on the water network and caused burst pipes across the south east region.
"Demand for water this morning was lower than expected and we're very grateful to everyone who cut back to help others".
Leak detection teams remain out in force across London to find further leaks and get them repaired as quickly as possible.
The companies are attempting to fix problems for vulnerable customers first and are providing bottled water where necessary.