The Medway Handyman wrote:
What is it with plumbers & fibre washers in tap connectors?

Its actually rare to find one. Usual practice seems to be to wrap loads of
PTFE tape around the bottom of the connector & hope for the best.

Helping my daughters bloke remove entire bathroom today prior to refurb, not
one single tap connector had a washer, all bodged with PTFE.

Bearing in mind a bag of 100 is only £3 why don't people use them?

The theory with fibre washers is that water leaks down the thread to
them, they get wet, swell and seal the connection. The theory with PTFE
tape is that water does not leak down the thread to begin with.

Colin Bignell