10-10-2024, 07:42 AM
The tank has a vent. It is almost certainly clogged if the tank is collapsing. The vent will typically have an in-line charcoal filter to prevent the smell from venting out but allow air to pass freely. When the filters get old, and especially if they get wet, they no longer allow air to pass through. Start by replacing the filter. If that doesn't work, you will have to dig deeper to figure out where the blockage in the vent line is. The vent line allows plenty of air movement to prevent suction from building in the tank during pump-outs when operating correctly.
