A valve is a device or natural object that regulates directs or controls the flow of a fluid gases liquids fluidized solids or slurries by opening closing or partially obstructing various passageways valves are technically fittings but are usually discussed as a separate category in an open valve fluid flows in a direction from higher pressure to lower pressure.
Water valve flow direction.
There are probably regional and or industry specific variations to this but as far as north american potable water goes this is it.
Check valves also called non return or one way valves are designed to allow flow in only one direction and to automatically prevent or check back flow if the fluid in the line reverses direction.
The globe valve is an excellent valve to use for on off service but is highly suited for frequent cycling and control of fluids anywhere in amount or volume between the open and closed positions.
Check valves tend to be small simple and inexpensive and are often used for backflow prevention in pumps safety applications and such.
It s important to orient the valve in the right direction with the arrow cast into the side of the valve aligned with flow direction.
If there s no existing valves and no clearance issue then the most common convention is to have the handle point in the direction of flow.
That way water flows against the bottom of the rubber gasket.
If the valve is put in backward the flow will force the gasket away from the top of the valve.
Most types are not operational and therefore do not have control handles.