Holding Tank Vent

[US1Fountain]

Can a spring loaded check valve be installed to an unused fitting on top of my holding tank to aid in venting the tank during pump out? I know it physically will work, just unsure if it will seal to keep from leaking odors within the cabin. Is there a check valve made for specifically for waste systems? My existing 3/4" vent hose, Sealand odor vent canister and thru hull vent are not capable of passing as much air as needed to prevent from creating a vacuum in the tank when I use the dock side pump out facilities. If I remove the nozzle right away, I get a small amount of inrush air, so I assume that I have to be collapsing the tank a bit. Never looked, but seems highly likely. I prefer not to install a 2nd thru hull vent if possible, but not totally against it if it is the only cure.

Simple design, dock side pump out capabilities only.

Thanks