I am removing a bathroom fixture that was attached to this cold water supply line:

alt text

I need to plug the pipe so it doesn't spray water when I turn it back on. Previously it had this fitting:

Original fitting

I tried this cap, but it leaked quite a bit.


I searched through many fittings at the hardware store, and finally ended up with this valve:


which worked (except when I put it on backwards, then it squirted water out, ack!).

It took 4 trips to the hardware store to arrive at this solution, and it's not really ideal, since I never want to turn it on. What would an ace plumber have done instead?

  • Could I have improved my question by making the pictures smaller? They seem to dominate the post. On the other hand, I hate squinting to look at tiny pictures.
    – Jay Bazuzi
    Jan 11, 2011 at 6:48
  • I've decided that I'm happy with the valve, because it makes it easier to drain the plumbing completely for winter, or flush the plumbing to sanitize.
    – Jay Bazuzi
    Jan 13, 2011 at 0:29
  • Gray pipe usually (always?) means it's polybutylene. That's an important point when trying to do repairs, as you need special couplers to do it right.
    – joshdoe
    Mar 7, 2013 at 15:56

4 Answers 4


Jay, it looks like you have a typical RV compression fit PVC line there. Looking at your pics, I don't see any pipe threads on the end of the tubing. It is difficult, if not impossible to match a threaded fitting to this type of pipe. You might have to go to a RV supply with the pipe type(usually printed on the pipe) and purchase an end cap for that specific tubing. If you don't have a pex tool or compression plyers to install a collar, there may be a self sealing compression fitting much like a Shark Bite that can be installed with a wrench, or a simple glue on cap fitting. Be sure to remove any scored or damaged tubing end before trying to install a new fitting.


I would normally try to go for a pushfit endcap of the right diameter (e.g. you might need 15mm). Something like this:

alt text

(product description: Conex Push-Fit 301 Stop End Cap 22mm. Joins a wide range of tubes including copper, carbon steel, stainless steel and plastic including PE-X and polybutylene.)

  • Definitely go push fit if at all possible. Home Depot carries the Sharkbite brand (homedepot.com/p/t/100638158) for under $10. Note however that these work with copper, PEX, and CPVC, but aren't approved for polybutylene, which has slightly different dimensions. It appears the Conex one does support PB however. You can also go to a plumbing supply store and get a Qest end cap.
    – joshdoe
    Mar 7, 2013 at 16:03

I would have thought that there would be an end cap for the system. It would look like the elbow and T-junctions you all ready have and would just fit over the end of the pipe.

Have you got any spare pieces you can take to the hardware store to compare to make sure you get the right one?


Looks like PE-X to me. Look for a cap that fits inside the pipe and then you will need a crimp tool and a copper ring to put crimp on the outside of the pipe. Warning - those crimp tools can be expensive. I think mine cost around $100.

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