Numpty question I'm sure but it won't be the first time. My system is unvented and at 1 bar. How can the can empty fully? Surely its only until the pressure equalises?
You have to drop the pressure out of it to get it into the system properly. If you stick it in through the filling loop, make sure you top up with water to flush the chemical out of the loop. Valiant will not accept rapid dose treatments for their extended warranties for their boilers, I'm not sure this is because they are less effective. Your probably better of using a liquid treatment for better results. P.s. I'm not sure what other manufacturers think about them. Intergas would probably accept rapid dose.
I'm was thinking of Sentinel X100 rapid dose. I think once its in the system its the same as any other X100 product isnt it, its just the concentration that varies? Anway, bought the standard stuff for now and will part drain a towel rad and put it in that.
Not sure if it's the same or not I just know some manufacturers will not accept it for water samples. Either way your doing the right thing and the easiest thing by putting standard x100 in through a towel rad, if you notice the water is orange or brown when your draining the rad it may be worth giving the entire system a quick flush before adding the sentinel. A coupl of hours work now can save a whole heap of hassle later on.