What is a Ball Check Valve?

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  • Written By: T. L. Childree
  • Edited By: R. Halprin
  • Last Modified Date: 30 November 2019
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A ball check valve is one of several different types of valves designed to permit the flow of material in one direction only. This type of check valve typically utilizes a spring-loaded ball inside a valve body. When pressurized material flows through the valve in one direction, the ball rises to allow passage. If non-pressurized material begins to flow in the opposite direction, the ball lowers to stop the unwanted material. Ball check valves are one of the simplest forms of one-way valves and can be used for many different applications including fuel and water pumping systems.

A typical ball check valve consists of a round ball inside a two piece valve body. The interior walls of the valve body are usually conical to allow for precision seating. A check valve ball may be constructed of either metal or artificial ruby. Some types have a permanent valve body with replaceable inner components. The inner ball may be attached to a conical spring or allowed to move freely inside the valve body.


A spring-type ball check valve is typically employed as a means of controlling the directional flow of high pressure material through a pipeline. When pressurized material passes through the valve in a forward direction, the valve is opened by pushing the ball against the spring. Non-pressurized material flowing in the opposite direction is unable to move the ball and its passage is therefore blocked. Freely moving balls in check valves rely solely on material flow for activation. When low-pressure material flows in a forward direction, the ball is moved upward to allow passage; when material moves backward, the opposite action occurs.

Ball check valves are generally installed in small-capacity water, gas, or fuel supply systems. Although many different types of check valves are available, ball check valves are generally less expensive to purchase and repair. This type of valve is also frequently installed in small diameter piping systems. Check valves are generally used to maintain line pressure in a fuel, water, or gas supply system during pump inactivity. These valves are also utilized to prevent the main supply of material from becoming contaminated by backflowing material.

A specially designed double ball check valve is also manufactured for certain types of applications. This check valve contains two balls in the same valve body to ensure a complete shut-off of backflow. The double-ball design is particularly useful in preventing contaminated material from backflowing into the main supply. A series of two ball check valves is sometimes used to maintain adequate sedentary pressure in long sections of piping.


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Post 2

@Feryll - Some mowers do have a ball check valve that allows gas to get into the carburetor and the engine. Once the fuel is in place, the ball blocks the opening and keeps the gas from pouring out of the mower. If this value goes bad, you will know you have a problem because the mower will not hold the gasoline. Even though the mower might run, the tank will soon be empty.

The thing with mowers is that replacing a whole part is easier than trying to repair it sometimes. The mechanic may have been straight with you. You should always ask for the old parts when you have doubts about whether the work was needed. This does not guarantee that you will not be taken advantage of, but having the old piece might help you see the problem better.

Post 1

My girlfriend and I just moved into a new house, and her sister gave us a used lawn mower for the yard. The mower hadn't been used in a couple years, but it appeared to be in good shape when I looked it over. I took it to a lawn mower mechanic to have it serviced before I tried to start it for the first time. I expected the mower to need some work, but I was hoping regular maintenance would be enough to get it running.

I ended up paying more for the job than I wanted to pay, and more than the mechanic told me the job would cost originally. In the beginning he said he wouldn't

have to do anything major, but then he said he had to replace the carburetor because the ball check valve that controls the gas flow was broken and the entire carburetor had to be replaced.

I don't know much about mowers or fuel lines or engines. Does this sound legitimate, or was I taken advantage of?

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