Cooling Server Rack with Water? Sensible? Reuse energy for small installation?

First - this is not a shopping question and not about concrete prices but about general feasibility. It makes no sense to look for a manufacturer if the approach is bad.

I am moving my company to new offices in September, and during the move we will expand and consolidate our computing cluster. Right now it is in a data center, but I have a nice room in the basement prepared for it.

I think about cooling. We will likely use around 10kw of power by end of the year. That is a LOT of heat, and cooling will be expensive. I am located in south Poland, close to the German border. This is an area where water is available for a relatively cheap price - "wasting water" is not a concern here. My situation is thus different from, for example, a company in Spain ;)

Physics tells me that to heat 1 liter of water by 1°C I use 1 Calorie (1KCal), and 1kWh is (and we can assume 100% efficiency - water heaters are pretty efficient) 750 Calories. That means that 1kWh is 750 liters heated by 1°C. 10kw and a 20° increase in heat would mean that per hour I need 375 liters. That is 6.25 liters per minute and not THAT much ;) We're talking 270 cubic meters here. Even in summer, the underground pipes really cool down the water a LOT more ;)

Is such an approach feasible? Has anyone done this? We have a 10kw installation for now. Is it feasible to reuse that heat? The alternative is a decent cooling system that WILL use around 2.5kWh to run. Dropping the water would:

1. Get me a quite cold input compared to the outside air, even in summer (I.e. a lower temperature medium to drop the heat in)
2. Replace the need to dump heat into the outside air, which may be problematic. If the air is 22°C, that is a LOT to fight off, but OTOH the water will be quite cold. I also would possibly save the investment for the outside part of the cooling circuit.

Now, second question - is there a feasible way to heat a house with that? ;) After all, it is a LOT of energy in that water ;)

If this is a bad idea, I'll stop here. If it is not, I'll start looking for suppliers. Maybe my math is wrong?