Regular pressure drops in central heating

[tally100]

Hi All

so today no heating again this morning , took cover off boiler no indication of water in the boiler , checked all rads and controls when cold no leaks , pressure 0.3 topped it up and it fired and worked ok, its dropping 1 bar over night with no indication of a water leak, only option i had was to add leak sealer to see if that fits it, no leaks from PRV so where is all this water going to. Boiler less than a year old and has Vaillant 9 year guarantee but they no charge £90 to come out and if its not the boiler you don't get a refund so if leak sealer doesn't work wha next.

1- plumber in to have floorboards up to find a leak or

2- Valiant out to check boiler is ok at £90

any other ideas

Thanks

Tally

 

[tally100]

ok i out some miracle seal ct1 in last friday and it not dropped enough to cut the boiler out, i put it to 1.4 bar cold 1.8 bar hot and its been ok until last night as before i went to bed it was 0.8 cold , ok today

i still can't seen how its a small leak as the amount its been dropping it should be coming through the roof