Had a really filthy house and conservatory to clean today. Did the front in the usual WFP way but attached up to their outside tap for the first hit on the conservatory. Cleaned the conservatory down, when to rinse with pure water but was interupted by an important phone call.
15 minutes later I went to redo the conservatory with pure water as it has dried. Examined it and there wasn't a single spot on the whole conservatory done with tap water. This house is local to me so will probably be on the same mains, my tap TDS is about 30. Didn't get a chance to test theirs.
Is 30 ok to use, it certainly looks it if theirs is 30 too? Will test it next month.