Heating Help

How do I flush a system before installing a new heater

I am about to replace the conventional electric water heater that was originally installed to head the slab in my basement apartment with an on demand water heater. This was installed with no air removal valve, no expansion tank and a litany of other short cuts and the pump has finally burned out. I've just removed the old pump and I see some white and green mineral build up in the flange.

My question is: Do I need to flush the system to remove the build up. If so, what is the best way to do that and how do I prevent the scaling from happening in the future. This is a closed loop radiant system in slab on grade using PEX and copper.

Thanks for your help!

you should

be fine if the water quality is fine. But why are you unsing a tankless water heater to do the job ? Its the wrong "tool" for the job. You would be better off w/ a gas fired tank type water heater than a tankless/demand water heater.