If its actually coming from the spout of the tap then probably the tap washer needs replacing, unless you were referring to washers as 'O'-rings (not a critiscism, just a query).
If so, are the replacement washers the right size? Maybe it needs reseating...
Sometimes the tap seat, which is what the washer closes against, can become pitted over time by air in the water imploding during pressure changes encountered at pipe restrictions such as washers or gate valves.
Re-seating means scraping back the seat to an even surface and is a relatively simple job as long as correct tools (tap reseating tools) are used.
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