Valves are everywhere – they’re hidden behind your walls, unseen in your ceiling, and sitting quietly in your basement.
And as long as they’re working properly, there’s no need to pay them any attention. You probably don’t give them a second thought.
Maybe you should. They’re essential for home, business, and industry, helping to control heating, cooling, manufacturing, water distribution, and much, much more.
This article introduces the basics of valves – common types, what they do, and how they work.
What are valves?
Quite simply, a valve opens and closes to control the flow of a substance – be it a gas, liquid, or slurry – typically through a pipe.
This is what valves do:
- Stop and start a flow
- Reduce or increase flow
- Change the direction of flow
- Regulate pressure
Valves come in a variety of types – ball, gate, globe, plug, butterfly, check, diaphragm, needle, poppet, spool…
The three most common valves are: ball, gate, and globe.
From the outside, a ball valve looks like a ball with a pipe stuck through it and a handle on top. Inside the valve is a ball with a hole through it (hence the name “ball valve”) – turning the handle turns the ball to either allow flow or stop it.
A ball valve is called a quarter-turn valve, because all you need to do is turn the handle exactly ninety degrees to open or close the valve. When a ball valve is positioned correctly, it seals. Tightening (or loosening) a ball valve too much causes it to leak.
See a ball valve in action in this video from Walworth Valves:
Ball valves are compact compared to other valve types and can withstand high temperatures and pressures. They can be bi- or even tri-directional and they’re good at sealing tightly, but they’re not great for controlling variable flow or throttling.
You can find ball valves on the gas line into your home, in large-scale oil and gas pipelines, and controlling the coolant in HVAC systems.
Gate valves work by raising or lowering a flat gate across the inside of a pipe. They are taller than ball valves, to accommodate the full size of the gate when it’s raised.
When a gate valve is closed, the pressure of the flow against it will actually make it seal more tightly. This makes gate valves a fantastic choice for shutting off flow through a pipe because they won’t leak under high pressure like other types of valves. Gate valves are not a good choice for throttling or regulating flow.
Like a ball valve, tightening a gate valve won’t make it seal better. But unlike the ball valve, which is a quarter-turn valve, a gate valve is a linear valve because it operates by moving the gate up and down in, well, a linear way.
See a gate valve in action in this video from Walworth Valves:
Gate valves are the valve of choice for water management, sewage, steam, and power plants, where the processes deal with high pressures, and the pipelines need to be either completely sealed or completely open.
Globe valves are more complex than either a ball valve or a gate valve. They typically have two chambers inside, with a plug that blocks the flow between them. Like a gate valve, a globe valve is a linear valve because it works by raising and lowering the part inside that controls flow.
A globe valve can either seal completely, allow partial flow, or open completely to allow unimpeded flow. This valve is designed for – and excellent at – controlling flow and throttling. Unlike ball and gate valves, a globe valve seals better the more you tighten it.
See a globe valve in action in this video from Walworth Valves:
You can find a globe valve on your garden hose and in your sink faucets. Globe valves are especially popular in the chemical and power industries, for precisely adjusting flows under high pressures.
All valves basically do the same thing – control flow through a pipe. Ball valves are simple to open and close, gate valves are good at shutting off flow, and globe valves are good at throttling.
Whether it’s turning on your shower, shutting off your gas line, or using your air conditioner, the right valve is in the right place is unremarkable, but it’s still important. Even if you forget it’s there.
Heather is a former engineer and project manager who’s worked on multi-year pipeline programs, valve repair projects, and public safety awareness mailouts. She loves diagrams, schematics, graphs, spreadsheets, and explaining them in a way that anyone can understand.