Well the slab gets poured on Wednesday so I thought I would sink 6 meters of copper pipe in the slab so that I can run my water loop through it when the house is finished. I hope to have water year round at about 16deg. No need for radiators or fans with chilled water coming straight out of the slab Hope there isnt any condensation issues but I dont think the water will be cold enough.... Any ideas on how I can measure the heat in watts that this can obsorb over a period of 3hrs? some pics: Click to view full size! Click to view full size! ---------------------------- Results are in: here are the results for today: test start time 9am Water temp at start 10 deg (after 10min of running the pump with no heat load). Water volume in the revserve 2litres, water volume in the loop .5 to 1 litre. Total volume 2.5 to 3 litres. Heat load 150 watt fish tank heater. This will simulate very closely the heat load I will be putting on the system as i7 creates about 130 watts of heat. The test system is still running but I don't think it will change from 17 deg that it has been running for the last 4 hours+ Click to view full size! So what does this test tell me / what can I expect? Firstly, Tasmanian agricultural areas (soil) have a mean annual temperature of 11-13 deg C. So I can expect the concrete foundation to sit at about 14-16 deg year round. When the house is built adding a few deg for ambient heat in the house. I have shown that this system will hold 150 watt load at about +7 deg above concrete temperature. So I can expect water for my PC cooling loop to be about 21-23 deg C year round. I was hoping for a bit lower in the range of 16 deg and I'm sure this would be possible with a longer loop. My current water loop (standard setup with 120.3 radiator and CPU block) sits at about 10 deg above ambient air temp giving me 29-31 deg C coolant temp. After all those variables are taken into account. I can expect to have chilled water 8-10 deg C below my current water loop which should give me quite a lot more head room for overclocking and best of all NO NOISY FANS blasting air through a heat exchanger. A big thanks to the people that posted constructive comments and offered help with this project Click to view full size! Click to view full size! Click to view full size!