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Vacuum Valves

Yahoo Message Number: 72253
Can anyone explain to me the exact purpose of the vacuum valves. I know that they allow air to pass into the tank and prevent air/gas from escaping. It seems to me that if somehow they "burped" in other words allowed a very brief escape of gas this would not be the cause of substantial gas into the coach.
Could you cap these off and open them when you went to dump? If that worked maybe you could install a solenoid valve.

John

2007 Inspire 52028

Vacuum Valves

Reply #1 –
Yahoo Message Number: 72267
John:

Regarding the fuel tank, there will be a net vacuum present as the fuel is consumed. However, on my rig there is a vent hose which is dangling under the drivers-side fuel fill access. The vent can be clogged with debris so it should be checked. I believe the cap vents in combination with the hose to offset the vacuum without introducing foreign material into the fuel system. I am sure there are pundits out there who will respond with more technical details than provided here. However, check the vent hose.

Dale Ford

04 Intrigue 11713
 

Re: Vacuum Valves

Reply #2 –
Yahoo Message Number: 72275
Dale The vacuum valve referred to are the ones under the sink. They are in place of a regular vent line on the plumbing. On motorhomes , it is hard, if not impossible to vent, the plumbing lines. Since each device ( sinks ) have water trap under each sink to prevent sewer smells from coming back. The tank is usually vented to the roof, but when you dump the tanks , you can possibly have more suction , than the vent to the roof, and if there were no auto vent after the trap, the water could be sucked out of the trap, there by allowing smells from the grey tank to come back into the coach. The auto vent near each sink would then let air in . The, question , was not about the fuel tank but rather the Auto-vents near each sink in the plumbing system.

Ron Baran 09 Magna 7025