We have a bathroom faucet (a couple years old), and the hot water side began to drip from the faucet (i.e. it was as though we were unable to shut off the faucet completely). Until I had a chance to replace the cartridge, I turned off the valve for the hot water under the sink. The valves look mildly corroded (photo below), and when I turned it off it did feel slightly stuck at first to start turning it, but after that point it turned fine, and it shut off with no problem.

Now, before repairing the faucet and ultimately turning the valve back on, the question has come up of whether turning it back on could end up being a problem, out of concern for us doing a non-emergency repair possibly then necessitating an emergency plumber visit: That is, since it is corroded, might turning the valve back on, or on and off at different points in the repair job, cause the valve itself to leak? How concerned should we be of a risk for such a leak in this sort of situation? And would the concern be for a large leak or a small one and only if it’s in the on or off position or always?

Hot water valve

2 Answers 2


There is a decent chance that the valve will begin to leak where the stem passes through the packing nut/gland. Not uncommon at all and you will need a bucket to contain the water until you can get the supply shut down upstream. Sometimes it sprays everywhere until you can wrap a rag around it. Sometimes the leak will stop when you either open fully and "back-seat" the valve, or when fully closed.

You already know the valve won't give a tight shut off, why not change it out right now while you are in there working. Install a high-quality 1/4 turn valve.

  • To clarify, the valve under the sink shut off fine, it was the faucet itself that didn’t shut fully, hence shutting the hot water valve under the sink. Does that change anything? Regarding replacing the shutoff valve itself, I don’t know how to do that. Although I can learn. But if I do that and make a mistake, I imagine that I’d end up in the same situation that I was trying to avoid by not simply using the corroded one in the first place. Not sure if any of that changes your answer, or if you have any further advice or recommendations?
    – A L
    Commented Mar 11, 2021 at 6:27
  • @AL if you have two wrenches and can rub your head and pat your belly - heck you don't even need to do that. If you can hold one hand still while moving the other, you have all the skill you need to replace that valve. The only potentially "hard" part is that the next valve upstream may shut off water to the whole house. Not that turning that one is hard, but if you have to take the valve off to go to the store to ensure you have a matching replacement, you may have cranky house-mates if the water is off too long.
    – FreeMan
    Commented Mar 11, 2021 at 12:20
  • Hmm, yes that changes things. I understood it that the stop-valve was leaking by. If the valve works fine and is left undisturbed, you may very well have years of service left without a problem. In fact, it will probably sit there and be fine until the next time you use it. Commented Mar 11, 2021 at 20:46

That greenish corrosion is probably due to a small leakage at the connections. I would try to tighten the compression nut just slightly and also tighten the compression nut on that flex line. You could take a soft brass wire brush to remove that greenish stuff. The way you explained the operation of turning off that valve is how those valves normally work or at least how mine work. Just make all the connections are tight.

  • The risk-reward calculation can help you to make the decision - the reward is how much you can save if you chose not to replace now, and the valve works just fine; the risk is how much is for an emergency service call, including parts and inconvenience, if it fails unexpectedly.
    – r13
    Commented Mar 11, 2021 at 20:52

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