The company said groundwater levels had been falling following a dry, warm spring, despite heavy rainfall during autumn and winter.
Affinity Water said it would contact customers seen using hosepipes to remind them of the restrictions.
People who fail to comply, which is a criminal offence under the Water Industry Act 1991, could be fined up to £1,000 in the magistrates’ courts.
The firm said it would be investing in new pipelines to reduce bursts and keep more water in the ground.
A spokesperson said: “By not using your hosepipe, you’re helping protect the environment and support people with urgent water needs in your community.”
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