# How can I make sure that my outflow is the same as my inflow?

I have a basin that is 110 mm wide, 200 mm long, and 15 mm deep. The walls are 2 mm thick. It has water being pumped into it at a rate of 0.1078 gpm from one side. In order to ensure that this pan does not overflow, how many 1.5 mm holes do I need to put at the bottom of this pan (Q outflow = Q inflow)? I’d ideally like to have the water drip out rather than stream. It’s also possible to change the diameter of the holes because I’ll be 3D printing it. I’m new to fluid dynamics and I need some direction!

• The best way is to do a test Commented Sep 26, 2023 at 14:18
• yeah, no way you will get this right via equations. Commented Sep 26, 2023 at 15:13
• To give you some direction on how you might test this: make a 3d printed version of your basin with a lot of 1.5mm holes in it. Then, fill up most of the holes and put water in the basin. Start unplugging holes until the flow is as you desire. Commented Sep 26, 2023 at 15:40
• Seal your basin. Inflow and outflow will both be 0. Need some inflow? Seal everything except outflow hole(s) and the inflow hole and fill completely. Also if the only concern is overflow, why not just use a tall hole. When level exceeds it, outflow will eventually equal inflow. You can reroute to the bottom...
– Abel
Commented Sep 27, 2023 at 0:14
• @Chris_abc might just have to do this since I’m struggling to figure it out with just equations… Only problem is I don’t own a personal 3d printer, so I have to outsource the printing and want to get it right in one go.
– Skuz
Commented Sep 27, 2023 at 16:37