Carmarthenshire is served by 1 water company, and a ban is set per company, not per county. The county is genuinely the wrong unit of answer: your postcode decides.
Welsh Water could not be confirmed, so check with them directly. Which of these applies at your address depends on which one bills you.
We could not confirm Welsh Water’s current status from their own page, so we are not asserting a restriction. Check with your supplier before using a hosepipe.
Check with your supplier
Areas covered: A single supply zone in west Wales, about 33,000 properties: mid and south Ceredigion with parts of north Pembrokeshire and north Carmarthenshire. This is NOT a Wales-wide ban.