Plumbing question

[Beluga]

So math has never been a strong suit and most tables I’m able to refer to don’t have the proper sizing.

Wondering for a 17mm outflow (gravity fed) and 17mm return, what sort of gph return pump am I looking at? Let’s say 12-18” of head space.

 

[Doctorgori]

So math has never been a strong suit and most tables I’m able to refer to don’t have the proper sizing.

Wondering for a 17mm outflow (gravity fed) and 17mm return, what sort of gph return pump am I looking at? Let’s say 12-18” of head space.

Heck I’m in the USA just like you; and equally metric impaired. I’ll take a stab at risk of being wrong: anyway since 2.54cm = 1” or 1mm = .04 inches and 17 x .04 = .68 inches
...Sounds awfully close to 3/4”
Heck any decent pump suitable for head pressure should work for 18” ... as a baseline: a MJ 1200 is gonna give you a decent blast at that height

 

[Beluga]

Yeah I believe 17mm is about 5/8” maybe?

thinking about it makes my head hurt lol.
So I can expect about 280-300gph to be sufficient to drain and return?