Inlet Problem - non return valve? HELP!
 

Hello

I have a water tank where water is being pumped in and the outlet is at a height of about 1 metre above, the outlet is relatively small and requires a small velocity but when i set my velocity small such as 0.2 ms^-1 i get an overflow error.

I thought this to be due to the pressure from the 1m height of water forcing water back through the inlet? if this is so can i set the inlet to not alow any water back through it? like a non return valve.

Thanks in advance