Flushing the rad
 

I've got a brand new heatercore that I've just modded to fit my 1/2" ID tubing to, and I want to flush it out to make sure there is nothing inside that might flow out into the loop and ruin my pump or clog up my block. Shaking it around I don't hear anything inside, but I really don't want to take the chance.

I assume I should flush it through both ways (intake to out and out to intake) a couple of times just to make sure, but my question is what should I use to flush it with? I don't want to connect the full loop back through the intake of the pump, because if anything does come out I dont want it getting into my pump, but at the same time I need some flow to keep the water moving. I think my only option is to connect tubing from the faucet to the pump and then the rad, and just have all the water dump into the bathtub or something, to insure that if anything does come out it doesnt go back into something that it would cause harm to. The only thing I am cautious about is what regular tap water will do to the inside of the copper core when flushing it. I'm sure that some water is going to end up getting stuck in the core, but I don't really want to risk galvanic corrosion. Should I maybe just get a couple gallons of distilled water and feed that through the pump/rad? If so, will there be enough force to keep moving the water through without any flow to keep it going?

Flushing or soaking overnight with tapwater won't oxidise the heatercore or leave any deposits in it, if your water is drinkable. If you really question the tapwater's purity then after flushing steam the heatercore off in a hot oven and for heaven's sake quit taking showers in that stuff.

I think most people just use a garden hose outside.

boiling water works very well, though hard to do

Galvanic corrosion happens very slowly. Flushing with tap water will be fine for the time it will be on your bench. Other deposits from tapwater may leave a small residue, but again nothing to worry about for the time spent testing.

Well, what is considered a "safe" cleaning agent?

I do apologise. I posted quite a lot that wasnt relevant to the previous poster and deleted it, My bad, I cant read :) Wow you caught it quick!
(This is in reference to using a cleaning agent to remove any residue from manufacturing processes that may be left on the pipe walls.)

I couldnt define what will be safe for your system as it depends what the component parts (ie seals, tubing...) are made from. I'm more of an electronics/software man than chemicals and research issues along that line as I come across them.

Using a very mild detergent (few drips of washing up liquid in the water) for about 24hrs total while testing hasnt had any negative effects for me in the 6 months my system has been running. I also didnt flush the system before refilling with ionised water, there is a real tiny amount of washing up liquid left in still (I can see little stacks of miniature white bubbles in any air pocket when the pump is stopped, they remain for a long time).

Longer term problems may still occur with rubber cracking maybe but for me I'm not too worried as it gives me an excuse to try something new. Also my radiator was used and you may end up with a larger concentration of detergent in your system if it hasnt anything to work on, should you have a new radiator.

I would recommend mild washing up liquid water if flushed out after and the seals wiped clean, or you can push your luck like me :)