We have a well and a storage tank. If we have more than one use of water in the house (i.e. two showers) at once the water pressure is extremely low. Can I test the Storage tank to make sure it is working properly? Thanks!

How big is the tank and what type, bladder or pressure. Bladder tanks have a valve stem on top for pressurizing the tank. Pressure tanks are usually unpainted galvanized tanks.

You can do this. Use water until the pump cuts on, then turn off the faucet and let the system build pressure. Once the pump cuts off, meaning the system is at full capacity, start running a hose into a gallon, or even five gallon, bucket. You should be able to get at least five or six gallons before the pump cuts back on. The amount you should get is dependent on the type and size of tank you have. If you can tell us the type/size of tank you have, a more accurate answer can be had, but 5 gallons is a fairly good rule of thumb.