Water started gushing from under my bathroom sink for no apparent reason. Why, and what's the best way to get this (potentially large) problem fixed?

June 26, 2012 7:38 PM

Water started gushing from under my bathroom sink for no apparent reason. Why, and what's the best way to get this (potentially large) problem fixed? Details inside, obviously.

So I'm eating dinner, and I hear quite the noise from a bathroom down the hall. Hot water's gushing from under the sink...very, very fast. After quickly turning off the water to the entire house, and doing the cleanup, I discovered the water had forced the supply line loose, and the water was coming from the now-unhooked-to-the-faucet supply line. This was a very random happening; I didn't do anything in the house that was out of the ordinary. I turned on the sink to wash my hands about two minutes before the gushing began, but it was a perfectly normal situation.

The problem was with this one bathroom sink only; the rest of the sinks and showers did not misbehave.

The questions, then, are: Why did the water pressure suddendly skyrocket in this one particular area? Can I turn the water back on in my house (while turning off the valves to the sink that is problematic) without causing any major damage to the system? Is there a simple fix I could do (flip a switch, ideally, or perhaps turn a knob), or should I call a plumber?

posted by st starseed to home & garden (7 answers total)

I would turn off the valve to the hot water supply line, turn the water back on to the house. Examine the end of the supply line that connects to the faucet - and check the threads on the faucet. Perhaps the nut on the supply line broke? In any case, if the threads on the faucet look (or feel) ok, i would get a new supply line - hook it up - and try opening the valve to that supply line. If it holds, you should be fine.
posted by nightwood at 7:47 PM on June 26, 2012 [1 favorite]

You can definitely turn off the valve to your sink (just turn the knob closed) and turn the water on to the rest of the house, Nothing bad will happen there- just make sure that the valve isn't leaky by looking for dripping after you turn the water back on to the rest of the house.

You will need a tool or two to actually replace the supply line (I don't remember the names of them, but basically, you need something to grab the line and let you turn it properly in the narrow confines of the sink- if fussing under a sink is not your thing, a plumber will be in order to actually fix things.
posted by rockindata at 7:52 PM on June 26, 2012

Not only turn the hot water in-line feed off, but also, turn down the temperature of the hot water heater. Your poor insulation contributing to the boiling water in the hot water heater most likely didn't help. Then turn the hot water heater back on. Replace all the hose connections that failed. It's summertime, you don't need the water that hot.
posted by vozworth at 7:57 PM on June 26, 2012

While you're at it, take this opportunity to replace all (or at least those for your bathroom - two for the sink, one for the toilet (especially the toilet!)) with Floodsafe connectors.

They're designed to prevent exactly this kind of problem, though usually it's the toilet connector that fails (because it's a plastic nut on the toilet tank which gets old and brittle and fails).

On preview, an overactive hot water heater with faulty/stuck temperature/pressure relief valve can easily cause the hot water pressure to rise. Or merely a cycling in hot water temp would cause a cycling in hot water pressure which could work the hose loose? Definitely worth getting a professional to look at it.
posted by jpeacock at 8:02 PM on June 26, 2012 [1 favorite]

The pressure probably didn't skyrocket.

If the line you are talking about is the one downstream of the stop valve. then there is the possibility that it was installed too tightly, and strained the metal flange where it goes into the nut that screws onto the stop valve. When the metal flange failed, the plastic hose popped free and the stop valve was now free to water your bathroom without that pesky hose.

The lines that connect the stop valve to the lavatory fixture are finger tightened, and then turned one turn beyond that. People often overdo it.

In this case, the nut will still be on the stop valve, and the end of the plastic or metal braided line will be nutless.

The nut itself could have failed, but that is less likely. You'll be able to tell when you examine the remains closely.

Remove the line that failed (it has screw fittings on both ends, one on the lavatory fixture, and the other on the stop valve, which has failed), take it to the hardware store *with you* to find a replacement, of the right length with the right sized fittings on the end.

It is likely that you will not be able to use the faucet until you replace the line, and will have to leave both stop valves closed. The hot and cold water are mixed by the faucet, and if the line to one side is open, water will pour out of the side that is supposed to feed the hot side, as well as the faucet.

And like everyone else said, check your water heater TPS valve (temperature/pressure safety valve) to make sure that is operating. The only way I have ever seen them fail is in the open position (they stay kind of drippy instead of closing all the way).
posted by the Real Dan at 8:06 PM on June 26, 2012 [2 favorites]

Please understand that I am not trying to talk down to you. I am just trying to address your problems as I see them. Based upon the questions that you asked, I believe you don't clearly understand the answers that you have been given up above. BTW, the Real Dan has given a really good answer. If you don't clearly understand the answers, it is time to call a plumber. If you make a simple mistake in the repair, it might hold or it might pick that time while you are at work to fail. You were lucky that you were at home when it failed this time. On the other hand, if you clearly understand and have access to the right tools, go for it. Fixing stuff is fun.
posted by Old Geezer at 8:22 PM on June 26, 2012

It's possible but very unlikely that this had anything to do with the water heater. Moderate cycling of water temperature as described by jpeacock should not have any noticeable effect on water pressure if the house is plumbed correctly, because the increase in volume either backs out into the city supply lines (if the house doesn't have a pressure regulator), or into an expansion tank (if it does have a regulator).

I'm with The Real Dan; it's much more likely that there was no spike in pressure, and the failure was caused by a faulty or improperly installed flexible supply line.
posted by jon1270 at 4:44 AM on June 27, 2012