Gate valve for Red Sea Reefer 625/750?

[ajtomase]

So...I've got no clue what I'm doing when it comes to plumbing, but I want to replace the diaphragm valve with a gate valve system. Does anyone know what parts I need to get for either a Red Sea Reefer 625 or 750?

 

[SPR1968]

You just need to know the downpipe size, in my S650 the main is 40mm so I installed a 40mm gate valve