Corrosion - how dangerus is it?
 

I have mostly cobber in my setup, but my T setup is in another metal, I don't know what metall, but another.
I planning to use dd watter weter and distiled water.
Am I headed for trubble??

And distilled water is the same you use in car-batteris?

No, It seems as if you'll be just fine. The T is probably made from brass, and brass is mostly copper.. The WW + battery water will be just fine.... :)

Thats good, I used a little fortion on those T's :)

Heres a picture off it:
http://hesbynett.no/sivlh/eee.jpg

That doesn't look much like brass to me, as for corrosion, it depends on the standard potential of the metal, the normal problem is between alu and copper which have opposing potentials - they basically create a battery with the water as the dielectric. The problem is the alu corrodes as part of this. Hard to say what that metal is, silvery metals are pretty common and that could be a plated part. Water wetter should prevent any serious corrosion anyway so it should be fine.

Should I use some more WW, just to be sure?

You should use the correct amount of WW as indicated on the bottle or you'll hurt your performance. The corrosion inhibitors work fine with the recommended amount.