I can’t find the details of SPM online so somebody please correct me if I’m wrong, isn’t it high pH with an oxygen bleach? If it is then I would only use it on a fine handmade woolen rug with caution even with an acidic rinse.
its a mix of phosphate and washing soda ...and a bit of bleach .
These are things developed by P&G in the 40s as builders for the first versions of tide ... so its like 40s tide
But worse ... cause its got no wetting agents ... so u have rub and scrub it into the carpet for it work at all .
I see solutions have a proper range of modern detergents now ... youd be better off those ...if you must .