My question is how does an expansion tank work with a well pump and how do I install it into the well pump system I have now? I manually turn the pump on and off. However, I understand I can enable the pump to operate automatically if I install two things a relay and expansion tank. I understand the relay work with the expansion tank to sense pressure drops, but can you explain it in more detail as to how rely, expansion tank and pump work and what size expansion tank I would need. My present well pump is a 3/4 hp motor use to water a lawn which does OK manually. Thank you for your help in this area.