Dear Dan: Four 330ft loops sounds like a big shop. A few questions: How big IS your shop, where do you live, is it insulated, how much window area, is the slab insulated, is the roof insulated, did someone do a heat loss calculation for you? Before you take any simplistic advice, like yes or no, to your question about whether an ordinary water heater will work. You will need to know how much heat your shop will lose in btu/hr, so you will know what size heat source to buy. I can e-mail you some simple diagrams you could use if you were to use a tankless water heater and small storage tank or storage heat exchanger for recirculation purposes. It's not polite of me to advertise here, so please E-mail me or call 800 851 9891 & I'll send more information to you regarding brands of tankless water heaters & very, very efficient heat exchangers, which will supply all the hot water you need. Regards, Brian.