valliant combi mdl no cca?

i have changed the ch flow pipe due to a blockage 2mtr of pipe,previously i had it power flushed after fitting 6 new rads,added chemicals then drained it,refilled it let it run and then drained it and then added inhibiter via the ch flow pipe,filled up to 2br,turn it on,bled rads it all works fine, but after turning the CH off i get no hot water with the CH off and the pressure from the hot water taps low,but if i turn on CH i get hot water from hot taps.many thanks.