Of course you can, but a better question would be should you store and RV with the valves open? Evidently lots of people leave their valves open after the final dump to completely empty the tanks for storage. Or maybe they just forget to close them. This is a bad idea because from our experience nothing good is going to happen with the valves left open ANYTIME. If the tank is in use every creepy crawly from the sewer is going to enter the tank and RV through the toilet and sink drains. Open valves are an invitation to all manner of critters to take up residence in the tank. We have seen giant garden snails, little furry critters of all descriptions, snakes, lizards, bugs, ants and insects beyond count or identification. The larva of who knows what, bedding and nesting material for something, corpses and skeletal remains of just about anything small enough to climb in and seeds and nuts stored for someone’s winter. I don’t know how easy they are to get in, but I do know that only a professional hydro-jet cleaning is going to get them out. TankTechsRx will prevent all this from happening…because you have to keep the valve close to keep the TankTechsRx in and the vermin out. It will most definitely NOT take it out once it is in. Sorry about that. Close the valves.