Valve seal flush tank scale

A surface-mounted flush tank was descaled after more than 20 years. After descaling, the flush tank still leaks barely visibly, but it can be easily detected with toilet paper.

The valve seal could not be completely descaled, see photo. Could the remaining limescale be responsible for this?

Which agent should I use to descale the seal so that it does not get damaged itself?

Hi

Looks like a new gasket is due




Olli

Thank you, I just ordered it!

With the new seal, the problem is resolved. Thank you