Rubber Gasket Valves are a type of check valve (e.g. like the ball bearing check valve and spring-based check valve) and, while found on many water blasters, they are typically found on reservoir caps and less likely used to control water flow.
Parts of the Valve:
A rubber gasket valve is comprised of housing with an opening to which a rubber flap or gasket is partially attached to, often by some sort of adhesive. The key behind the design is the partial attachment of the rubber gasket to the opening; as rubber can stretch or deform when pressure is applied, this valve's ability to control directionality is heavily dependent on the geometry of how the gasket is attached which effects how much pressure it takes to open the valve.
Water Blasters that Use This Valve:
Some blasters that use rubber gasket valves include:
- Super Soaker CPS 1000 - part of the reservoir cap
- Super Soaker Monster XL - part of the reservoir cap
- Water Warriors Orca - part of the reservoir cap
When there is no significant flow of water (or air) in any direction, the rubber simply rests against the housing. It should be noted that often the rubber does not create a true air-tight seal with the housing which is actually good for the times when this valve is used in a reservoir's fill cap. By allowing air to be able to enter even at rest, this allows the reservoir to adjust to external air pressure differences and respond a little faster when air needs to enter the reservoir as water is pulled out. So long as the gap between the rubber gasket at the housing is small enough, water will not be able to leak out even if the seal is not air tight thanks to water tension. Of course, if the hole between the gasket and housing increases too much, water may leak out of the cap, but since most caps are at the top of the reservoir, a leak would only occur if the blaster were left on its side (or upside-down).
When air (or water) is pushing in the direction denoted as forward, the valve will open once enough pressure to deform the rubber is reached. 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 type and thickness of rubber commonly used in these valves, air (or water) can readily push through the valve.
Preventing Reverse Flow:
As noted above, reverse flow is prevented thanks to the geometry of the valve, namely the way the rubber gasket covers and is partially attached to the housing. When there is not enough pressure to open the valve in its forward direction, the gasket is designed to effectively seal the opening. When force in the opposite direction is applied, since the gasket extends well beyond the actual opening in the valve's housing, this increased internal pressure actually acts to seal the valve even more firmly.
As can be seen illustrated in the diagram above, there is no direct path for air (or water) to flow through the valve in the open state. Air (or water) must always deflect around the rubber gasket since the gasket 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 rubber gasket valve is simple and effective for specific areas. Its simple construction, however, has some inherent limitations. Rubber, while elastic, is a natural compound that tends to get stiffer and more brittle over time. Loss of elasticity reduces the ability of this type of valve to function. Even if the rubber, itself, is ok, the adhesive that is often used can end up dislodging, again reducing the efficacy of the valve.
Due to the valve's geometry, it is also more difficult to allow for greater flow rates through the valve while maintaining its ability to prevent reverse flow. That said, the simplicity and effectiveness of this type of valve makes it perfect light use situations such as controlled air intake into a non-pressurized reservoir.