I have recently plumbed up a live to work accommodation with 8 en-suits with showers and 4 shower rooms complete with w/c and whb's. I have ran two zones with 28mm pipe teeing off in 15 mm dropping down to 22 mm for the last two shower rooms. I have two 300ltrs unvented cylinders have come with 22 mm bsp thread on the hot water outlet. What will the result be ? I have it piped up not soldered yet.
Thanks
Carl

We need more details before we can give you a answer, Are you in the UK? *8 master baths complete with showers, Where are the other 4 shower rooms going in? What's the PSI in the water service?

I have two 300ltrs unvented cylinders Are we talking water heaters or storage tanks? What so the shower rooms consist of?

15 mm dropping down to 22 mm This doesn't make any sense at all. Please post back with more details. Back to you, Tom

Please, post TOTAL count of all plumbing fixtures ( specify number of each ) in the structure + incoming water pressure. Also, how many stories is this building ? How far from the water meter to the closest wall of the building ?

Back to you / Milo

Ok.
The dwelling Is two stories. There is 12 shower rooms complete with w/c and whb. There is no baths. I have 2000lts of stored water filled off the mains. This runs into a dual pump which feeds two unvented hot water pressurised cylinders and the cold. I have split the shower rooms into two zones upstairs and down stairs 6 and 6. I have first fixed running 28 mm pipe as far as the 4th showerroom on each level then reduced the size to 22 mm and continued on the run for the last two. I have teed off the 28 mmpipe direct to the outlets in 15 mm. The hot water cylinders have come with 22 mm bsp threads on the hot outlet at the top of the cylinders. What will the result be from this ? Or any information you can give would be greatly appreciated. Is there anything information I can give you.

Also,
Thanks for getting back to me lads