valliant ecotec pro 28 boiler. The pressure keeps going down!!?

Help the pressure on my boiler keeps showing F22 error code - came on here yesterday and followed the instructions on how to attach the pipe and get the pressure up and happily sat down in my nice warm house.

Woke up this morining and the house is freezing again - have once again attached pipe and got the pressure up again but dont want to be doing this everyday!!

Can anyone help???