doitall,
This is a possibility as I can create a "boiler room" in the new extension. Do you mean use a whole house pump or pumps to the individual showers? Also, no-one seems to give any replies on the Vaillant unistor. Is this a no-no?
Ta, carl.
Yes I mean a sectional storage tank, and a whole house pump set.
You can then pump the cold and the hot into an unvented cylinder or store at a set pressure of say 3bar.
Are you intending baths to be installed or just showers, if showers only then allow a combined hot and cold drawoff at each outlet (shower) of 30 l/min as a minimum, the shower valve data sheet will give you exact volumes.
I would consider a 28mm secondary circuit with a 15mm return.
Subject to further information I would say an single 300 ltr cylinder would be more than enough for the 5 bathrooms.