I have a Vaillant Eco Tec Plus 418 condensing boiler at the minute installed in a upstairs bedroom cupboard. It's serving a conventional open system with a skinny 1050 x 400 indirect cylinder in an adjascent cupboard. That's as big a cylinder as i can get in there. I'm sick of low hot water pressure and not enough of it to fill a large bath so want to change to an equally good quality Combi. Obviously as far as i know their are no leaks on the system which i installed 5 years ago but, till i test it i can't be 100% sure. I was wondering if i could keep the heating side open on the F&E tank and still have the benefits of mains hot water. I've had no problems with my Vaillant so probably go with another if suitable. Or, should i bite the bullet and turn it in to a fully sealed system even if it means finding any miniscipal leaks? Any advice please