Delta RP50587 Single Handle Valve Cartridge,Chrome,Small

We love our Allora kitchen faucet and the Delta lifetime warranty that comes with it. The faucet started dripping until you played with the handle a bit so called support and, within 5 minutes, the cartridge and retaining nut replacement order was placed under warranty. I flushed the lines as instructed and performed the replacement... like brand new again! I hope the replacement lasts as long as the original.

The original cartridge in my 2017 Leland kitchen faucet only lasted 2yrs before the drips started. The second cartridge lasted another 7yrs before failing the same way. Both times it took only a few minutes on the phone and Delta sent a free replacement. Kudos to them for standing by their product. I am a bit surprised that Delta did not come up with an improvement on the RP50587, but maybe they have moved away from this cartridge on new faucets. Seven years is good, but I have seen other similar design (ceramic valve) faucets last over 20yrs without leaking. This design uses two polished ceramic plates that slide against each other. The plates are forced against each other by the plastic case and partly by the faucet bonnet nut. When the holes in the plates line up, the water flows. When the movable plate slides far enough the holes no longer line up the water stops. On this failed cartridge there is no obvious reason for failure - the plate faces are still highly polished with no obvious scoring or wear on other moving parts - so why is it leaking? It is possible the plates while still polished, are no longer flat and do not mate well when moved around. There could also be tiny wear in the actuating parts that together prevent the moving plate from sliding as far closed as before. The forces that push the plates together may have lessened over time due to aging of the plastic/rubber pieces. Does Delta know what the failure mode is?