HERMS loop Vs counter flow

[Cain Harland]

I'm looking at putting together a HERMS rig. It will probably be single tier so have 2 pumps. Given that during mash 1 pump will just be recirculating the HLT water I have been thinking why not do away with the HERMS loop and use a counter flow chiller instead, an all metal one. With the HLT water in the outer loop and mash in the inner. There is probably very little in it in terms of price by the time you buy the extra valves, bulkheads and compression fittings for the HERMS.

Can anyone give me a reason why this is a bad idea and a traditional HERMS loop would be better? Eg is the outer loop going to have toxic shit in it because the cooling water usually goes down the drain so I wont be able to use it for sparge.

I would probably find a suitable old pot or something and set the chiller in it in expanding foam to stop it acting like a heat sync in the air. Will probably insulate mash tun too either with wooden slats like a barrel or by placing inside a slightly larger pot (the cheapest thinnest one I can find) and filling the gap with foam.

Also I  go the HERMS loop way then for cooling how much less efficient is cooling by running the wort back through the HERMS loop while running the garden hose into the bottom of the HLT and out the top. Rather than cold in, hot out like counter flow or immersion, its cold in mix out so clearly less efficient, but would it make any real difference or do I just waste a little more water?

[Cain Harland]

Thanks good to know cooling that way works that's probably what I will do if I go with the coil