[newowneroldmontana]

I have a 2002 3670RL. I bought it old and used, with some modifications made by the first owner, so I don't really know what's original or not, plumbing-wise. I know pictures would help, but I just can't post any--so here goes--I'm going to see if anyone can help me solve my problem even with the vague information I'm going to give:

My water froze up this week but eventually thawed on its own, and I thought everything was fine. Last night, though, I sprung a leak in the basement.

The problem is quite clearly with a blue plastic thing which I'm pretty sure is a shut-off valve. Going from left to right, there's pipe that's kind of whitish/opague, then a fitting that looks like I ought to be able to unscrew it, then the blue plastic thing, then another fitting that looks like I ought to be able to unscrew it, then more pipe that's whitish/opaque.

The blue plastic thing had water spewing from it--I think it's a shut-off valve which froze and then broke. It's a plastic circle with a raised area meant to hold onto in order to turn it. I know that I've turned it and shut off water to the toilet before, but I could still get water to the sink and shower while I didn't get water to the toilet. Last night when the blue thing started gushing water, I lost water to the sink. (I mean the bathroom sink. I don't know about the kitchen sink.)

Does anyone know what I'm talking about? Can I just go to Lowe's tomorrow and buy a new blue thing/shut-off valve, and replace the leaking one? Can I really unscrew those fittings? How does one splice in a new shut-off valve(?), or a new short length of RV water pipe?