Well that kit comes with 2. So I guess I would do 1 more. I run a back up drain it sits alittle higher than the main drain. This allows you to valve the main drain down a bit so the water level rises which makes it so much quieter. The water level is above the drain. You run a backup right next to it which is a bit higher so that if the main drain gets clogged or you close the valve to much it will catch the water. So 1 return 2 drains and you will never have water on your floor and it's dead silent. I believe this is kind of the herbie method I figured it out on my own my trial and error. The things you need to order are the 3 bulkheads 1ft of loc line 1 loc line fitting 1 nozzle of your choice round or flat and 2 bulkhead strainers