Ball Bearing Check Valves (also known as Ball Check Valves) are one of the most common types of one-way valves used in toy water blasters.They are perhaps the simplest and cheapest of the unidirectional valves to manufacture, explaining their use is almost all small trigger-based water blasters and even many pump-action water blasters.
Parts of the Valve:
Ball bearing check valves are comprised of a carefully shaped housing that surrounds a small, often metal or plastic ball bearing that floats freely within. The key behind the design is the shape of the housing that allows water (or air) to flow around the ball when the ball is pushed to one side while being sealed closed by the ball, thus preventing flow, when the ball is pushed in the opposite direction.
Water Blasters that Use This Valve:
Some blasters that use ball bearing check valves include:
- Most dollar-store trigger-based squirt water blasters
- Super Soaker Lil' Squirts
- Water Warriors Kwik Grips
- Aqua Force
When there is no flow of water (or air) in any direction, the inner ball bearing is free to move around, typically resting at the lowest point of the housing based on the valve's orientation and pull of gravity. Of course, if a blaster is being swung around, centripetal force may push the ball against a different part of the housing.
When water (or air) is going in the direction denoted as forward, the valve ends up in its fully open position. The term, forward, is used strictly relative to the direction of flow through the valve since the actual position of the valve may have it facing upwards or even towards the back of the full water blaster. Due to the light weight of the inner ball bearing, it is easily pushed by moving water or air. Thanks to the shape of the valve housing, small catches on the front-side of the valve catch the ball bearing in a way that still leaves a number of gaps between the ball and the wall of the housing. Thus, though the bearing can no longer move any farther forward, water and air can easily pass around it.
Preventing Reverse Flow:
When water or air attempts to flow backwards through the valve, they will end up pushing the ball bearing to the back side of the housing. Unlike the forward position, the shape of the back side of the house forms of tight seal when the ball bearing makes contact, sealing the opening and preventing much water or air from going through. While there is a slight lag between the open and closed states of the valve, the amount of air or water allowed to flow in reverse is typically quite negligible compared to the amount of water pushed forward.
As can be seen illustrated in the diagram above, there is no direct path for water (or air) to flow through the valve in the open state. Even when fully open, water (or air) may enter straight into the valve, it must then deflect to go around the ball bearing, pass the small ball bearing catches, then exit through the out port. As the ball bearing must be larger than the hole it seals, little can be done to improve flow lamination through this type of valve.
Strengths and Limitations:
The ball bearing check valve is perhaps the simplest and cheapest way to create a unidirectional valve for controlling water (or air) flow through a system. Since only properly shaped plastic housing and a tiny metal or plastic ball bearing are needed to build a fully functional valve, the cost per valve is typically very low.
While the seal to prevent back flow is not always perfect and lamination of flow through the valve leaves much to be desired, as most of the valves are rather small in size, the negative effects to overall water flow are not very significant. That said, due to the physics behind how these valves work, increasing their size to allow more water to flow through when openreaches its useful limit fairly quickly. As ball bearings get larger, they are most costly to have perfectly round and tend to get heavier, thus harder to push into the right position to properly open, but more importantly, when closing the valve. When a ball bearing gets larger, if the reverse flow is not forceful enough, but consistent, the flow may not be strong enough to push the ball bearing backwards to properly seal the valve closed, thus resulting in failed unidirectionality. Thus, while these type of valves work fine for small, trigger-based water blasters and light pump-action water blasters, they are not as suitable for water blasters where larger rates of flow are desired.