Water Heaters - hot water heater for radiant heat

I just installed a new gas,40 gallon water heater. I recently discovered that a certain kind of hot water heater can be used for radiant heat. I would love to run pex along all the joists in the basement to heat the flloors on the first floor of my home.What is the most economical way to do do this? Will I need to buy another hot water heater? Is there a smaller hot water heater on the market for doing just one floor.

rebeljeep: From your post I don't think you know what you are getting into; you can't just run pex to your floor off your heater and expect it to work.

You have to run controls, reflective shields, insulation and do a heat loss calculation on the area you are trying to heat; then you will have to check the heater to see if the there is enough capacity. If you still want to do this go to the library, they should have books that will give layouts, luck.

Thanks Shacko,I did look at several websites like this one http://forum.doityourself.com/water-heaters/374615-hot-water-heater-radiant-heat.html I realize that it's not as simple as running pex off of a hot water heater,but some of the pictures I'm looking at look pretty straight forward. There is hardware that holds the pex,controls,etc. My old hot water heater sprung a small leak this fall. That thin pool of hot water on the basement flloor heated the whole house. It was cold outside and I had to turn off the heat and open the front door.