You must have turned the hot & cold water supplies off in order to change the washer and I`m sure the DIY Doctor site will tell you about trying a re-seating tool.... take the valve assemblies out as before then look inside the tap opening at the brass seat for each valve assembly. If you see cracks - often look black against the brass seating - then you definitely need to re-cut the seats. Tool is available from Screwfix, B&Q etc for around Â£10 and has cutters to fit two tap sizes.
Select the cutting disk to suit the tap seat size (one is for bath tap and one for basin tap) and fit into place on the tool. Carefully screw the body of the seating tool into the opening until it is firm - not wobbling about. (Don`t damage the internal thread of the tap by catching it with the disk - but if you do just apply some PTFE tape to the valve body before you refit it!) Then carefully but firmly turn the tool head/handle round in a clockwise direction and you will feel the "teeth" on the face of the disk cut some of the brass seat away. Turn it perhaps twice then unscrew the tool and check the seat for shiny and continuous brass facing. Repeat as necessary but don`t go mad and press too hard or too many times and so grind the whole seat away. When all is done it may be best to change the washers again lest they`ve been damaged by closing the tap onto that worn seating. Good luck EyeTry
Click on the link below to go to the project specifically on repairing a dripping tap. There is indeed a seat grinder in the tool boxes at the bottom of the page. Any tools required for any project you are working on can be bought by simply clicking on any of the tools on any forum page and searching for the tool you need.
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