More knowledge than I expected to receive

[DQDick]

They'll know, because it's a common problem. Low bidder valves. You have several choices. One is to replace it with a genuine OEM part. Two is to replace it with a good check valve, normally brass. Three is to eliminate it all together and go with a brass check valve on the outside. Three is what I did. I went to a hardware store and got a brass check valve of the type restaurants are required to use on their outdoor facets. I also got a small flexible connection that they sell to go between your hose and the faucet (usually has a spring around it to save the hose from crimping at the faucet). I use quick disconnects on all my water hoses so I put a quick connection on the end of the short spring hose to hook it into the black tank flush inlet then added the brass check valve then another quick connection and then I hook my hose to it.