Today I tried to have my house power washed and within less than half an hour my water pump was drained with no pressure reading on the gauge. AS I have done before, when pressure goes below about 20 lbs, I shut of pump. After it stands for a few hours it will usually begin to pump and fill my tank when turned back on. This time however I think it might need to be primed first. How do I do that? The pump is located in my basement.