Valves that have to work

Why. The packing squeezes the stem. Ease it, and your effort goes into the threads instead of fighting the packing.

The tell. Wheel keeps turning, water does not change? You dropped the gate. The stem spun out of the wedge.

That's straight off Crane's sheet for its bronze gate valves: if the handwheel is hard to turn, loosen the packing nut a quarter to a half turn, and retighten it once you're done opening and closing. The packing nut is the small nut right under the handwheel. Loosen it, counterclockwise, only that far. Don't reach for a cheater bar on the wheel. The wedge inside is screwed onto the stem, and forcing it is how a slow drip turns into no shutoff at all.

Why. Scale can jam an old gate in its seat. The gate is screwed onto the stem, so cranking it back open strips the stem out.

The tell. You open it back up, the wheel turns, and the water never comes back. The wedge is stuck shut and the stem spun out of it.

Plumbers call it dropping a gate. Plumber Magazine lays it out: shut an old gate valve and the barnacles on the disc crunch into the housing and jam it. The stem is screwed into the wedge like a screw, so when you spin the handle to get the water back, the stem spins out and the wedge stays put. The valve gets replaced. Their advice matches mine: close it very slowly, never force it, and if the water barely flows, do the repair that way. Richard Trethewey said it on This Old House about a stuck main: if you can't move it, don't force it, because nothing stands between you and full city pressure.

If the shutoff is seized and water is already getting out, our sister site Vent, Valve & Volt has a list of when to call a plumber, and how fast.

Why. Flow under the seat keeps line pressure below the disc when it is shut, off the bonnet and the packing.

The tell. No arrow you can read? Look into the inlet end. You should be looking at the underside of the seat.

A gate valve doesn't care which way it goes in; Crane's sheet says its standard gate valve takes flow either way. A globe valve cares. Apollo's sheet says the inlet end goes against line pressure, and Valves Online says it's built to take flow one direction only, under the disc. Wärtsilä's reference explains why: flow from below the seat keeps the upper chamber unpressurized when the valve is closed. When you shut it, bring the disc down on the seat and stop. Valves Online says if it still passes water, the seat may be damaged, and more wrench won't fix a bad seat. They also say don't leave it half open for long stretches; it wears the seat early.