I'm trying to install a new under sink filter and what should be a fairly simple installation is turning out to be a nightmare.

I've figured out most of the connections but what has me puzzled is something a plumber did a long time ago. It appears to be some sort of needle valve connected to the cold water pipe directly behind the cold water valve. The hose emerging from this goes into the old filter system.

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I tried to close this valve but no amount of turns in either direction did anything, it just spins in place. Engaging the cold water valve does nothing either. How on earth to I stop water coming from this needle valve???

  • 1
    If you can find a cap that fits, you could just cap off the output side.
    – FreeMan
    Jul 18 '20 at 18:55
  • The problem with just capping it off is that the valve itself has failed and you never know when it will start leaking. You could cap it but put it on your "to do" list to fix it right.
    – JACK
    Jul 18 '20 at 19:03

This is a classic “vampire valve”. These are cheap “taps” intended for low-draw things like refrigerator icemakers, drinking water filters, furnace humidifiers, etc. - and are to avoid the more serious work of plumbing in a proper valve. The whole point is to let the appliance installer do a “drive-by install” instead of doing proper plumbing. They are by nature retrofit/afterthoughts; no one would ever intentionally plan to use one when plumbing a building. They would fit a proper and normal valve for the icemaker, humidifier etc.

As such, anytime you are re-working plumbing in an area, it’s normal and expected to eliminate all vampire valves and replace them with proper plumbing.

If you are in a position to do that, you should do that.

Other than that, to avoid plumbing work, your only play is to clean up the pipe really well and fit another vampire valve right into the same puncture hole. Leave it shut, and don’t disturb it. Unless you need it for something.


If the valve just spins in place, then the stem is stripped and your solution is to remove it and plug the hole with a repair sleeve or just replace the valve with a new one and turn it off. This was a common way to add small filtering systems to point of use. The water to the house would have to be turned off to do either fixes.

  • 1
    Or, one would hope, the previous plumber was nice enough to put this on the sink side of the shutoff.
    – FreeMan
    Jul 18 '20 at 18:59
  • A plumber wouldn't fit one of those. they don't meet code. drftps.com/faq/are-saddle-valves-okay
    – Jasen
    Jul 19 '20 at 6:52

Turn off the water main, remove the saddle valve, cut out the damaged section of pipe, clean up the cut ends and surface. fit a tee where the cut is connect a new valve to the branch of the tee.

If the existing main cut-off valve can be re-fitted to the new cut end a tee and a reducer could be used after the cut-off valve.

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