Toilet fill valve shank sizes

[andyste]

I need to replace our toilet fill valve (bottom fill, brass shank) and I've noticed that most on sale have a 1/2" thread. I've measured the thread sticking out of the bottom of our cistern and it's more like 3/4" dia. Do we have an "unusual" size, or do I just buy one with 1/2" and put it down to one of these weird plumbing measurement things?!

Also, Will I need anything to seal the large plastic washers or will the valve come with rubber seals?

 

[HERTS P&D]

This is all you need:

http://www.screwfix.com/p/fluidmast...gclsrc=aw.ds&dclid=CI6F3-n0o9MCFVjhGwodjMgITw

Andy

 

[andyste]

So they are all a standard 1/2" shank then, despite me measuring it at more like 3/4"?

 

[HERTS P&D]

Yes

 

[oldbuffer]

1/2" on the shank size is really the size of the thread, which is 1/2" British Standard Pipe. It refers to the inside diameter of the pipe, which really is 1/2".