Bungalow HW routes?

Hi - I have a typical 1970's bungalow with pumped open system CH&HW with a cylinder located in the ground floor airing cupboard. The system works fine currently - except....the HW pipes are all laid in the original floor screed without protection and are very badly corroded. We are also planning an extension and will need new HW service there too.

My question - am I ok to route the HW services from the cylinder over the ceilings instead of breaking out ground floor screeds? I have a 28mm inlet / outlet currently on the cylinder, and proposed to tap into the HW cylinder vent pipe above the ceiling for the two bathrooms, and kitchen feeds.

From my limited understanding of physics, providing I fix the new pipes to falls to avoid air-locking, the system should function just fine - the pipe routes are not being made longer, and the pipe sizes would all be the same. I'd be grateful of your thoughts / experience before I plan any changes.

Thanks

 

Thanks All - I should have explained - the boiler will change to combi in 3 years time when we extend the other side of the house. I am looking to feed the new kitchen and two bathrooms overhead in the meantime, from the existing gravity cylinder. What factors should I be considering when looking to take an feed off the cylinder to run overhead?

G&W thanks for your help also, can you expand a little on the description of "you should take a draw off the hot supply below the open vent t on the cylinder for limiting air being pulled in". Should I draw off below where the vent taps to the cylinder? or anywhere below the top of the vent pipe?

Thanks All - none of this will be a problem in the finished house, but I need a simple solution for a few years!

Thanks