The creek is not very consistent. Right now it is at best an inch deep and a foot or two wide. Sometimes after a heavy rain it is 5ft deep and a lot of silt and mud in it. So anything I put in the creek will either get washed away over time or be buried in silt from the strip mines. The system I put together before was I think a 1/4hp sump pump running to a good size garden hose and the exit from the radiator('75 dodge polara) was also the same size garden hose running back down to the creek to keep the pump from having to lift the water as high. I figure the pump was putting out a lot more flow than it needed but it was just stuff I already had so it got put to use. If someone had a more consistent stream near their house a coil of copper pipe or old radiator put in the stream could probably be used to transfer the heat using a closed system and be pretty reliable. I did it mainly just to see if it would actually work, I was bored and had nothing better to do than mess around and build things. This summer I am just looking for excuses to play with the tractor
I asked a few people today and one guy says he could get me a used 10,000 gallon tank for free if I come get it. No idea how I would haul it in a Metro and the little Kubota tractor I have would take 6 months to dig a hole that size. But I did manage to find a potentially endless supply of 55 gallon barrels for free
So now the plan is dig a ditch wide enough for the barrels and keep them about 3ft apart and run the water through them in series. I have no idea how many barrels I need but I might get a few of them and bury them to run an experiment. I could probably dig a hole and put 2 barrels in the ground and hook up a working system in a day without a lot of effort. The two barrels would give me a better idea of how much heat each one could handle so I know how many actually need to be used. Then I could get that many plus a few extras and hook up a more permanent system.
I don't actually think this would save me much money in the short term though. My electric bills are pretty much always $35 a month since I haven't used a/c this year, ~$100 with heavy a/c use. I am just not in the house during the day to care how hot it is in here. Winter my gas bills max out at around $90 so really it doesn't cost much to just keep doing what I am doing now.