The new regulations came into effect from the start of the year and require landlords to inform Welsh Water about tenants moving into a property within 21 days of them moving in.
If this is not done, Welsh Water can make the landlord jointly liable for any outstanding water and sewerage charges.
However, due to the “short notice” of the new legislation being introduced by the Welsh government, Welsh Water will not take any enforcement action until 31 March.
Welsh Water’s managing director of customer services, Julia Cherrett, said: “We are currently working to ensure landlords are aware of this new duty.
“We want to make the process as easy as possible for new landlords. Due to the short notice of the new legislation, landlords are being given three month grace period by Welsh Water to help them prepare for the legislation and share the necessary details.”