Towards the end of our 6 month trip it was becoming more difficult to turn the 4 way valve. Actually had to use channel lock pliers to turn it the last week of travel. In addition, in Normal, the water pump ran constantly. Ordered the replacement core. Installed today. In removing the old core saw one whole rubber ring, and half of another, missing! Installed new core according to the below video. Very easy. The printed instructions say to remove the click washer, then the core. Skip and just remove the core.