The Shutoff Valve Under the Sink Is Stuck: What to Do

The small valves under a sink or behind a toilet are the ones you only touch in an emergency, which is exactly why they are stuck when you need them. Years of mineral deposits and a packing nut that has not moved since the house was built will do that. Here is how to free one without breaking it, what to do when it will not move, and why the right long-term answer is usually a new valve.

What the valve is and why it seizes

The valve under a sink or beside a toilet is called an angle stop, or a straight stop where the pipe comes out of the floor. Older ones are multi-turn compression valves: a handle turns a stem several rotations to press a rubber washer onto a seat. The stem passes through a packing nut that seals around it. Houston's hard water leaves mineral deposits on the stem and the seat, the rubber washer hardens, and the packing nut, tightened once in 1995, grips the stem like a vise. Turn the handle and nothing happens; turn harder and the stem shears or the handle strips.

Modern quarter-turn ball valves have a ball with a hole through it and a lever handle. They do not seize because there is nothing to compress and the ball rotates in seals rather than pressing against a seat.

Before you touch it: shut the main

Find the main shutoff for the house. In most Houston homes it is at the meter box near the street, which needs a meter key or a long wrench, or where the water line enters the house, often near the front hose bib or in the garage. Turn it off, then open a faucet somewhere to confirm the water stops and to relieve the pressure in the lines.

Now the stuck valve cannot flood anything even if it fails. Skip this step and a cracked valve body becomes an emergency.

How to free a stuck multi-turn valve

1. Look behind the handle for the packing nut, the hex nut the stem passes through. Put a wrench on it and loosen it a quarter turn, no more. This releases the grip on the stem.
2. Grip the handle and try to turn it closed (clockwise) with steady pressure. If it moves, work it back and forth a few times through its full travel to clear the deposits off the stem.
3. If it will not move, a few drops of penetrating oil at the stem where it enters the packing nut, left for ten minutes, often does it. Try again with the same steady pressure, not a jerk.
4. Once it turns, close it fully, then snug the packing nut back up until the stem does not weep. Do not overtighten; the nut should be firm, not strained.
5. Turn the main back on slowly and check the valve for drips at the stem and at the body.

A valve that frees up and then holds without weeping can be left in service, though it is on borrowed time. A valve that weeps at the packing nut after retightening, or that will not close fully, is done.

What not to do

• Do not use pliers on an oval handle or a wrench on the stem itself. Both strip or snap it.
• Do not heat the valve. A torch near a compression valve with a plastic or rubber interior ruins it, and near a flexible supply line is a fire risk.
• Do not keep turning a handle that spins freely. The stem has separated from the handle or the washer has come off the stem, and the valve is open regardless of what the handle says.
• Do not assume a valve that is "closed" is holding. Open the faucet above it and watch. A closed valve that still passes water is a replacement.

When to stop and call

If the main is off and the valve will not move with the packing nut loosened, the stem is corroded into the body. If the valve body is green, crusted or weeping at the joint where it meets the pipe, the connection to the wall is the weak point and turning the valve can twist the pipe. If the pipe behind it is old galvanized steel, the threads in the wall can shear when the valve is turned. All three mean a plumber replaces the valve rather than you freeing it, and in the galvanized case the plumber will want to see the stub before anyone puts a wrench on it.

Replacing the valve: what the job involves

With the main off, the old valve comes off the stub. How depends on the connection: a compression fitting unscrews and the new valve goes on the same stub with a new ferrule; a sweat (soldered) valve is cut off and a new one soldered or, more often now, a push-fit valve is pressed on; a threaded valve on galvanized or on a threaded adapter is unscrewed and replaced with thread sealant. The new valve is a quarter-turn ball valve. The supply line to the faucet or toilet is replaced at the same time with a braided stainless line, because the old one is as old as the valve.

Then the main goes back on slowly, the valve is cycled a few times, and everything is checked dry. A plumber does it in about twenty minutes per valve, and most people have all the valves in the house done at once if they are the same age, because they are.

Why this matters more than it seems

The shutoff valve is the thing that turns a burst supply line or a failed faucet into a towel job instead of a flood. A seized valve means the only way to stop water is the house main, which in a hurry most people cannot find or cannot turn. Every Houston freeze produces the same story: a line burst under a sink and the valve would not close. Replace the valves while it is calm and the next emergency is small.

A quick test for every valve in the house

Once a year, go to each sink and toilet, turn the valve closed and open again. If it moves freely and does not weep, it is fine. If it is stiff, loosen the packing nut and work it. If it will not move or it weeps, put it on the list. Do the same with the main and the water heater inlet. Fifteen minutes a year, and the valves work on the day they matter.