Hi squashpaco,
Thank you for your review of the Delta Faucet TRINSIC® Pull-Down Kitchen Faucet MODEL#: 9159-CZ-DST. Please accept our sincere apology for the inconvenience you are experiencing. We are always happy to assist! Quality is very important to us and our products undergo rigorous testing to ensure high-quality performance.  
Our products do have a Limited Lifetime Warranty that covers parts (other than electronic parts and batteries) and finishes of Delta® faucets purchased from authorized Delta sellers to the original consumer purchaser to be free from defects in material and workmanship for as long as the original consumer purchaser owns the home in which the faucet was first installed. I have included a link below for the warranty information.
https://images.thdstatic.com/catalog/pdfImages/78/78ba3a43-8314-4719-ad2e-21e705c32af3.pdf
We appreciate your business and look forward to continuing to serve you. Please contact us directly if you have any further questions.   
Best Regards,  
Kelley
Digital Communications Specialist