@ReneBogersREBO wrote:
Hi iainsavage,
Thank you for your extensive answer.
The valve family is valve-breaks into indeed, only question about it: what’s the difference between “Valve – Breaks Into” and “Breaks Into” at Part Type?
I already had a host family with the valve nested inside AND the flanges nested inside so I think I gonna stick to that, you also mentioned it like the better method. In this nested family each flange can made visible/not visible by yes/no, cause not always 2 flangs are needed. But when nog flange is needed, then I need the other size (150 instead of 160), cause connection to for example the mechanical equipment is a DN size.
Reason I was thinking about to change to separate valve and flanges was, cause they also used on their own, and with the extra nested family I have another extra family in project. The other reason was, revit has the opportunity to add flanges by routing preferences 😉
With the items mentioned above, I guess maybe it’s better to use ALWAYS pipe sizes (90, 110, 125, 160) instead of DN sizes (80, 100, 125, 150). What’s your opinion about this?
My preference is to use both, cause DN sizes come with a lot of ME/PIA and so.
Part type: I've never really understood the difference myself and the official help doesn't really clarify it

Pipe size with one flange: The valve would normally be 150mm (6") since it is probably the same valve which is used on different types of pipes and manufacturers don't, in my experience, produce a 160mm valve. So its the flange family that you need to modify. You could I think use a formula based on the setting of the yes/no parameter so that if it is yes the connector diameter is 160mm, otherwise it is 150mm.
Nesting or separate families: either method is valid. The advantage of nesting is that when placing many instances of the valve its a one click process rather than each time placing a valve, flange 1, flange 2, possibly having to flip the flange family, then align them to each other to remove/minimise the bits of pipe between each of the three components. As I say if you set the nested families as Shared then in terms of quantities etc the valve and flanges will still be counted individually.
Flanges in routing preferences: Yes you can also do that and it might work okay in your case but I find that the automatically placed flanges can be a bit unreliable and sometimes appear or disappear without you having control over them. It is a valid method if it works reliably for you.
Nominal versus actual diameters: I can only speak for UK where it is normal to use nominal sizes for steel and iron pipes but use external diameter for copper and (most) plastic pipes.