We have a Rheem hot water heater and the water seems to have pressure problem when first turning it on. Also, we lose the hot water before finishing a shower that is no longer than 5 minutes. Could this be the element?

Steve, please open a new post for your question. When you jump in on someone else's post it gets confusing.
Dforler, your heater may have two elements with one shot. Check both elements if there are two, I'm thinking you are only running on one at present. Can you tell us a bit more about your pressure problem since this isn't related to your element. Are all hot faucets low pressure? Have you drained the scale and junk out of your tank laterly?