Treated water smells inside, but not outside

I have an in-line pellet chlorinator w/ mixing tank, followed by a carbon filter. I'm treating for H2S. Water supply runs from the well, through the filters, into the house. There is also a tap for our garden hose, before it enters the house. We started out just putting 1ppm (80 gallon pressure tank, using hole #1), and the water coming from the outside tap smelled & tasted fine, but the water inside seemed to have a metallic smell & taste to it (that's the best way I can describe it). So we've gradually increased the chlorine input to now 15ppm (hole #3), and the smell & taste has reduced inside, but it's still there, even if only slightly. But now, water from the garden hose has a strong chlorine smell. Common sense is telling me that it must be the pipes feeding the house (old & mixed between copper & galvanized), am I correct in assuming this? If so, is it alright to replace the copper/steel with all pvc? If not, what else would be causing the metallic smell inside but not outside?

Thanks!

I trust your pressure tank is after your filtration system. Also do you know how old your carbon filter is and how big it is because it kind of sounds like the carbon is fouled and if you have iron in your water the chlorine will oxidize it and it will foul your carbon filter. You will want to use a different media to filter iron.