[notanlines]

Steve, you have gotten some good advice from knowledgeable folks. Now let's have a little fun with this. You made claim that your commode and black tank are still 'turd virgins.' (I just couldn't think of proper terminology) I'm guessing in the four years use of the RV, and literally hundreds of walks to the park bathrooms you have built up what extra worth in your RV resale? Are you actually going to put in the Ebay ad that your commode is....well, still a virgin? What about the sink? The Mattress? Water heater?
Yes, I'm just having a little fun at your expense. Feel free to send a little retort back at me. In the meantime, buy the endcap or the valve and don't sweat the small stuff.