There are similar projects i saw but I did it much more complicated and developed. You will recognize how it works after you examine the schema and video added.Note that I did not waste my arduino. It is not necessary for this circuit.

Material List

• 2 x Float switch - I bought them from Ebay about 2 dollars.
• 1x 12V 1A DC Power Supply
• 1x Sump Pump
• 1x12v Relay ( In order to control 220V cause we don't want to give our float switches 220V directly it is dangerous.)
• 1x Check Valve (If your pump is lower than your tank, you should use it to protect water returning to backet again)
• 1xLED

Why should relay be used ?

Float switches cannot be given 220 V AC directly It can deal with max 30 V (for security) and it is also dangerous cause our switches staying in the water so we are using 12V on switches and theycontrol the pump. It makes our system more secure. The switches works like AND gate. In order to pump water, both of switches must be closed(on transmission). If one of them is open, It wont pump. When 12 Volt goes relay(2 of switches are closed) relay will provide 220V transmission. You can also think relay as a switch.

Note : You should connect float switch itself which is in the bucket as reverse.(see schema) Cause while sensor in the tank should work when water is lower, the sensor in the bucket should not work if water is lower.(to protect motor waterlessness).

Video