Hi Kack,
Thanks for being a loyal Delta Faucet customer, and we appreciate your honest review of the RP21905! I am happy the product was exactly what you needed, and I am sorry you are experiencing an issue with the pump. We would recommend flushing the pump with a 50/50 solution of white vinegar and water to help remove anything causing the pump to be tight.
Your feedback is important to us, as it helps us refine our products and services. Please contact us back with any further questions.
Best regards
Nicole
Digital Communications Specialist