water loss

can anyone help me ? My 95 escort LX TD is losing water,but I can not find where from.Today I yet again filled her up and the water just disappeared so I started her and put in water and it stayed,I first noticed the problem when the heater packed up apart from the water she's a great car I am replacing the water every other day
Thanks

Check your heater core. They leak often times inside your car on the passenger side. I have had two fords that had heater cores go bad and start to leak.