Anyone interested in a bit of history of "20 mule team Borax" https://www.20muleteamlaundry.com/about
FWIW I've been trying to break into my filter for the last couple of weeks to see what's going on inside, but to no avail !
I've already broken my strap wrench trying to undo the half union joins and even gentle persuasion with a full sized pipe wrench isn't making any inroads either !!
p.s. I use the LaMotte tests-strips for borates. Can you get those?
I think 'mule team 20' is the brand of borax in US. Marion I'm sure can confirm for us Aussies. You can get it in Bunnings guys under the brand name of Glitz. $10 a kilo.