The point of a valve is to avoid the need for a leg (or night) bag. As you said, urine collects in the bladder as it would normally and you just open the valve over a toilet whenever you feel the need (or every few hours). I have not had prostate surgery so I'm not sure about putting strain on the bladder but that doesn't make a lot of sense to me. Just ask your urologist.

I'm not a medical professional but I did have RARP and my care team really stressed keeping the bag below your bladder so the urine can freely drain into the bag so it doesn't back up into your bladder and put stress on the stitches. Also, that's why the night bag is so big is so it won't fill up and stop the draining. It's also why I used the night bag during the day at home so I could lay around with my feet up and have the bag on the floor below my bladder. So I agree with @windrider354 that using it to go without a bag sounds like a real bad idea to me. My care team did give me a clamp (looked like dull scissors) to clamp the catheter for about 30 seconds when changing bags, but not for continuous use. If you do want to pursue this, definitely ask your care team before you do it, and make sure they understand how you intend to use it. But even if you didn't plan to go without a bag, having a valve that could get left shut accidentally (or get accidentally closed somehow) seems like a bad idea for a recovering RP patient. Just my 2 cents. Best wishes.

Soli - you have to use bag after the surgery since the whole point of catheter after RP is to make sure that urine drains constantly without any delay. There should be no strain on your bladder since your urethra was cut off and than reattached to your bladder. There will be a lot of blood in your initial urine and possibly some small cloths also. All of that junk needs to drain, drain , drain. This gentlemen was kind enough to explain his way of dealing with catheter placement and attachment. The rest does not apply for RP.