most installers now will opt for the combi as they are eaiser to install,nowadays people jsut want instant h/w my old adage is if the boiler breaks down(yes new ones break too )you have no back up,at least with the cylinder & immersion you can have some hot water and put another jumper on to warm up,
if you need the space where the cylinder is and the loft space where the jockey tank/cold water tank is then go for the combi option.
the vaillant is still the best but being caught by worcester look at the gloworm cxi which is the same as the vaillant only different badge although they wont admit it!
Hope this sheds some knowledge let me know if you need more info
Hi for what its worth, as a leckie who gets to connect lots of various systems it seems to me from customer feed-back that combi's OK for space saving but flow rate for hot water very poor, due to need to heat water instantly so heat exchanger design slows down water through put to give time to heat up sufficiently. Acceptable for sink or one shower but not much pressure so if longer runs or several outlets stick with tank, also as Toneyt says immersion heater good back up,regards SPARX
I fit Worcester-Bosch boilers only and I LOVE them although a little pricey. Fit a 30cdi combi condensing flow rate 14lts min that should do the trick but best system would be unvented cylinder and system boiler if space is not a problem
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