DHW manifold pipe sizes

[oldbutnotdead]

Getting towards dhw in the House of Pain.
Hot water source will be mains through a plate heat exchanger on the thermal store, supply pipe is 25mm into the house then 22mm to the hex. Pressure and flow both good.
Bathroom 1 (6 metres) will have bath and overbath shower and basin
Ensuite (16 metres) will have shower and basin
It is possible that both will be used simultaneously
Will i best mitigate pressure drops by running seperate 15mm feeds to each room from the 22mm output of the hex or should i do something else?
TIA

 

[Madrab]

If you don't want to see a flow/pressure drop then maximise pipe size where you can. The closer to the outlet you can get to in 22mm the better to minimise any fluctuations in flow. Though it all comes down to how good the dynamic pressure and flow are, as to how noticeable a drop you will actually see.

 

[oldbutnotdead]

If you don't want to see a flow/pressure drop then maximise pipe size where you can. The closer to the outlet you can get to in 22mm the better to minimise any fluctuations in flow. Though it all comes down to how good the dynamic pressure and flow are, as to how noticeable a drop you will actually see.

Ta.
My initial plan was doing it old school- 22mm to the bathroom then T off that to the shower room in 15 (the bathroom is at the back of the house, shower room at the front, thermal store/hex at rear right hand side so the run would work) - but wasn't sure if that would cause major issues in the shower room if someone turns on the bath tap. Sounds as if my best bet from your input will be to run 22mm all the way to the shower room and T off it in 15 for the bathroom? Reluctant to run 2 separate 22mm feeds (space as well as cost of tube), quite prepared to have a non-gushing bath tap in exchange for minimal pressure drop at the shower room (which is where my thought of separate 15mm runs came from)

 

[Madrab]

Putting the shower room first in the chain should give it priority but regardless it's all about dynamic pressure to ensure minimal drop regardless of pipe size. Just ensure you have balanced outlets etc, that coupled with a good quality shower with a good thermostatic valve.

You will always see a little drop in pressure/flow, unless you have like 6bar dynamic mains with a 3bar PRV giving it loads of reserve.

 

[oldbutnotdead]

Ta again- the geography puts bathroom first so it would T off the 22mm run at about 6m from hex, 22mm then continues another 9 metres ish to shower room.
Was trying to get dynamic pressure & max flow this afternoon but something is a bit frozen somewhere...when the polar vortex sods off I'll try a couple of test layouts in the garden (think I've got enough pushfit couplers, def got a roll of 15mm barrier in the library). May not get absolute numbers but I'll get relative values which will do. Might also have a google & see if I can find pressure drop figures for water (like the tables for gas)

EDIT Found quite a cute one. Short version- 6m of 22mm at 10l/s gives a drop of 10mB, the same length of 15mm with the same volume flow drops 70mB. Not sure what the starting pressure is on the calculator......think I have to download the Excel version. Tomorrow.....