Geothermal Closed Loop Question

I have a 3-ton Climatemaster closed-loop geothermal system with two 300 foot wells.
I was in the process of having Sonotube footers dug & in the process, one of my well pipes was severely nicked by a shovel. So I opted to have it repaired. My well guy cut out a 2-foot section and heat fused it in place. The system was purged and topped off & works well.

My concerns is we noted the color of the antifreeze had a dark hue & wasn't blue like it was when the system was filled back in April. I also noticed the inside of the piece of pipe we cut out has what looks to be a rust film. I'm not sure where the rust is coming from. Anyone have any idea(s)? I contacted the well guy. He used water that was process through an ion exchange unit & had a ph of 7.5. He said an additive could be added, but is it necessary in a closed loop system where Charter Plastics geothermal pipe 3408-C-3-
dr-11 was used?

are you on well water, the film could have been iron in the system, it could also be bacteria

maybe the iron is coming from a grundfos pump or another ferrous element in your system

Abby, I don't understand what you mean by the iron coming from a grundfoss pump, could you elaborate.

Expat, remember Grundfos pumps come in lots of different sizes/materials.

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Originally Posted by expat

Abby, I don't understand what you mean by the iron coming from a grundfoss pump, could you elaborate.

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When you use the small circulators on an open system, they are usually made with bronze or stainless.

The OP is using high density PE pipe, it is a closed system, but could still be a little prone to oxygen diffusion. If the pump is ferrous you could get some rust.

the monoethylenglycol will just eat away at any ferrous metals in the system, this could be the pump itself or any mild steel fittings.

You prob already know this so if it was me I'd be having a look at the pump as abby says and check to see what it is made from