Replacing a toilet system

My present toilet system upstairs and downstairs operate not from the water mains supply but from a tank in the loft and when I installed them a good few years ago I had to fiddle with the water inlet to allow the water to fill the bowl.

I’m looking at a replacement Flush King top flush, bottom fill which says that Fill valve minimum operating pressure 0.2 bar, maximum operating pressure 5.5bar. Would this operate on my water inlet system from a tank in the loft OK?

One bar of pressure is approximately equal to 10metres head of water, so 0.2 bar is roughly equal to two metres head. If you measure the vertical distance (in metres) from the bottom of your cold water storage cistern to the top of each WC cistern and divide by 10, you'll get a pretty good idea of the water pressure, in bar, at each cistern inlet. Assuming a room height of about 2.5 metres, you should have no problem with the downstairs WC, the upstairs might be marginal but would probably work anyway.

I measure from the bottom of the water tank to the top of the upstairs wc cistern to be a little over 60cm so about 0.06bar so it might be a problem. Anyway many thanks for your reply. I will have to think about it. If I do the downstairs wc first , I could first try a separate test connecting a water connection 60cm above the bottom entry valve and see if that works ok maybe that would tell me if it would work.
Dugit