Here's what you need to understand.
The car's cooling circuit should ideally seal. i.e once it is filled with water / coolant you should forget about it.
If the car is loosing water, that should point you to find out where the water is going !
a. Like you pressurize the AC cooling circuit and then wait for 30 mins or so to check for pressure drop; same needs to be done with water system; except you need to wait more than 1 hour. If the pressure drops then there is a leak some where which you need to find.
Since you have checked the hoses, you need to pay attention to radiator find for a small leak.
b. check if water is mixing with oil; you need to check for frothy oil, or water with traces of oil in it. In this case you need to fix the gasket and have the head refaced again.