What will cause the wet tank air pressure to leak down overnight?

When discussing why a faulty one-way check valve would cause the wet tank air pressure to leak down overnight, it’s important to understand the role of this component in the air brake system. The one-way check valve allows air to flow in one direction—typically from the air compressor to the wet tank—but prevents air from escaping back into the compressor or the atmosphere.

If the one-way check valve is faulty and fails to seal properly, this can lead to a situation where air trapped in the wet tank can escape, resulting in a gradual loss of pressure over time. This is particularly significant during the night when the air pressure is not being replenished by the compressor due to the vehicle being idle. Consequently, the wet tank would show a noticeable drop in air pressure by morning, indicating a leak path that should otherwise be sealed by a functioning one-way check valve.

Additionally, while other components like a faulty air governor valve, service brake diaphragm, or a leak in the air compressor outlet line can cause air pressure issues, their effects and mechanisms are distinct. For example, a faulty air governor valve may prevent proper management of compressor operation, but it wouldn't directly create a leak from the wet tank. Understanding these distinctions helps pinpoint the specific cause of air pressure loss