i'm using latex plus with mapei keraquick adhesive to tile my wet room floor. can i add water to the mix as well to make the latex plus go further? it's expensive stuff...can't find any advice on the latex plus info page

I wouldn't, and I've never even considered it to be honest. Why not give mapei tech dept a ring?

you can't to be honest,as it wouldn't be the same adhesive the latex is to create a 2 part adhesive or 1 part in some cases if you are diluting it then you are not creating the required flexability and are crating an adhesive that is between either non flexi/flex or flexi/2 part if that makes any sense

simple answer no

The 6Kg bottle mixed with 20Kg of powder is designed to give performance to EN12002 as S2.
If you dilute it you will also dilute the performance in service.