Thousands of homes remain without water after "unprecedented" issues following Storm Ciarán.
More than 18,000 properties across Southampton and the New Forest lost their water supply on Thursday evening.
Southern Water has confirmed 7,000 homes have since had their supply restored, but issues caused by low pressure after the storm are continuing for an estimated 11,000 homes.
The firm said properties on the Isle of Wight might now also be affected.
Southern Water has released an update stating a potential 4,600 customers in Ventnor "may experience a temporary drop in pressure or intermittent loss of supply".
The firm said this was due to work being carried out to restore water supply in Hampshire as the network is connected.
It confirmed all customers in the affected area in Ventnor had received bottled-water deliveries "as a precaution".
Southern Water has set up four bottled-water stations in Southampton and the New Forest, which are open through the day.
It is also using water tankers in certain areas and delivering bottled water to priority-service customers and encouraged people to stay up to date via its website.
The stations are based at:
Applemore Leisure Centre, Hythe, SO45 5TN, closes at 21:00 GMT
Gang Warily Leisure Centre, Fawley, S045 1GA, closes at 14:30
Staplewood Football Development and Support Centre, Marchwood, SO40 4WR, closes at 17:30
Jones Lane Car Park, Hythe, SO45 6DU, closes at 21:00
Elsewhere, Sunnyfields Farm in Southampton has opened its gates for people to use its water refill station and toilet facilities until 17:00.
Farm owner Ian Nelson said: "We've opened 14 toilets, including changing facilities, there's hot running water, we've opened our drinking station and there's a kitchen hatch for free tea and coffee if people bring down a mug.
"We'll be open again tomorrow if we're needed; somehow the farm is on a different water main so we're one of the lucky ones."
Southern Water previously explained rainfall caused "unprecedented issues with the raw water quality" in the River Test.
As a result, a shutdown was triggered at its Testwood site, which meant water could not be abstracted and treated for drinking.
Holbury resident Maureen Cranny said she had been without water and heating since 20:30 on Thursday.
She said: "It makes you realise how precious water is and to be careful how you use it.
"You can't help the rain coming out of the sky, but I have been puzzling, when you consider all these flooded areas across the country, how is it their water supply companies have managed to keep going and ours haven't?"
Tim McMahon, water managing director for Southern Water, said the team had been working "incredibly hard".
He said: "It's difficult to know exactly when all customers will be back in supply. It does take time, we've got to be careful it doesn't cause other problems and keep a very close eye on the water supply works as it's still very fragile."
Mr McMahon said they expected customers water supplies to be restored on Saturday, but there might be low water pressure on Sunday.
He added: "Clearly, apologies to all the customers who have been impacted, it's horrendous not having water and it's not acceptable - we know that.
"Unfortunately, it's the extremities of the weather that has caused this incident. We are looking at putting other things in place over the next year which will reduce risk further, but it's going to take time because these old assets need a lot of work to get them to the level they need, but we are working very hard to solve it now and in the future."
Southern Water advised customers to prepare for their water to return and said those leaving their homes should make sure that taps are switched off to prevent an accidental flood.
The firm also said that as water returns, it might temporarily appear discoloured, cloudy and white, or have a chlorine smell or taste.
If the water has a brown or black colour, customers should run the tap for a few minutes until clear or wait for 20 minutes and try again.