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Apologies in advance for being a bit less prepared asking this - sudden change of plan... Also this is a bit long 
In the process of renovating and extending an oldish house, and replacing all plumbing (and most else but that's beside the point). The main issue is the showers... Attic has been converted to a bedroom with shower room, and there is also a shower on the first floor - and it seems a bit pointless to have two if they cannot both be used at once. The boilder will have to go on the ground floor.
The pipe length to the first shower will be about 12m with a rise of about 5m; then the second shower is 6m further on and 4.5m higher. My calculations (using the info. in Treloar's book) suggest 22mm to the first shower and then 15mm from then on, with a loss of head of about 0.9bar to the 1st one and 1.5bar to the second - I've included the rise in this which I assume I should. There is of course other stuff as well as two showers, and I included that when working this out, and I don't expect any system to keep up with max. possible demand.
The supply pressure is just over 4bar, and a basic test of the flow rate (i.e. running a bath tap into a bucket) is 27l/min. All this seems OK, provided whatever source of hot water we end up with can keep up with the required demand.
So, our choices seem to be unvented cylinder, thermal store, or a high output combi - it would be impossible to get enough head for a gravity fed system. Presumably an unvented cylinder would be fine? Thermal store? I must admit the idea appeals but have read that they are better suited to u/floor heating - and we have radiators. What about a high output combi? The flowrate of some of them seems OK, but am not sure of the pressure. All I've been able to find out so far is stuff like "hot water output will be to spec. if incoming water pressure is at least 1bar" - which could imply that output pressure would never rise above 1 bar (totally useless); or that output approaches mains pressure (which would be OK); or something in between (which might or might not OK).
Thanks in advance for any ideas and suggestions,
Neal
In the process of renovating and extending an oldish house, and replacing all plumbing (and most else but that's beside the point). The main issue is the showers... Attic has been converted to a bedroom with shower room, and there is also a shower on the first floor - and it seems a bit pointless to have two if they cannot both be used at once. The boilder will have to go on the ground floor.
The pipe length to the first shower will be about 12m with a rise of about 5m; then the second shower is 6m further on and 4.5m higher. My calculations (using the info. in Treloar's book) suggest 22mm to the first shower and then 15mm from then on, with a loss of head of about 0.9bar to the 1st one and 1.5bar to the second - I've included the rise in this which I assume I should. There is of course other stuff as well as two showers, and I included that when working this out, and I don't expect any system to keep up with max. possible demand.
The supply pressure is just over 4bar, and a basic test of the flow rate (i.e. running a bath tap into a bucket) is 27l/min. All this seems OK, provided whatever source of hot water we end up with can keep up with the required demand.
So, our choices seem to be unvented cylinder, thermal store, or a high output combi - it would be impossible to get enough head for a gravity fed system. Presumably an unvented cylinder would be fine? Thermal store? I must admit the idea appeals but have read that they are better suited to u/floor heating - and we have radiators. What about a high output combi? The flowrate of some of them seems OK, but am not sure of the pressure. All I've been able to find out so far is stuff like "hot water output will be to spec. if incoming water pressure is at least 1bar" - which could imply that output pressure would never rise above 1 bar (totally useless); or that output approaches mains pressure (which would be OK); or something in between (which might or might not OK).
Thanks in advance for any ideas and suggestions,
Neal
