What is the best method to clean out the coolant system?

[Gorilla]

Hi everybody,

Previous owner ran water and its a really tasty rust color (sarcasm) anyway i need some advice as to whats the best thing to use to clean it out before i put in coolant?

I dont want to use nasty chemicals if possible.  Also anybody with good ideas to clean out the coolant tank? i usually take them off and flush them with hot laundry detergent and srub them with a bootle brush then flush for as long as i cannot smell laundry powder.

[Geoff Weeks]

After flushing as best you can, install a coolant filter if the engine doesn't have one. Flushing gets the loose stuff out, the filter removes the stuff that wouldn't come loose at flush time, when it does come loose and starts circulating.

[Joey Mack]

And it can add a PH conditioners as well. I like coolant filters...