Hi, just wondering if anyone can give a little advice please. Had an issue with my washing machine where it wasnt draining. Looked and found a hairgrip jammed in the impeller of the pump. Removed it and all seemed fine. Now this morning noticed some water in the drum (door was open) and now wondering if it has come from the sink? Does the sump hose between the drum and pump have a one way valve in it to prevent back flow from the undersink drainage? Also if this is the case where is the best place to get a replacement from as the ones I have found when searching do not look the same. TIA