Long hot pipe runs (second HW cylinder?)

[lookseehear]

We're starting to plan pipe runs for new bathrooms in our extension/renovation project - as a reminder everything is moving around due to going upside-down and house is being rewired/replumbed.

 

DHW cylinder is going in a small plant room in one of the new extensions which is on the corner of the house. In total the hot water requirements are the kitchen plus 3 shower rooms (ensuites), one 'family' bathroom mostly used by guests and one small WC. The bathroom layouts in the below sketch are not correct, but the room positions have not changed.

 

 

The red circle is DHW cylinder and the red lines are likely HW pipe runs to 'family' bathroom, ensuite 2 (shower room) and the kitchen which is above the boot room and Ensuite 2. I had assumed we would run 22mm for all the main pipe runs and branch off to 15mm to maintain flow, but I've now realised that in the kitchen that could be a 15m+ pipe run in 22mm and would take half a day for hot water to appear at the tap, and the same problem in ensuite 2 and (to a lesser extent) in the family bathroom.

 

What I want to try and avoid is the shower in bathroom 2 being severely affected by the kitchen hot tap being used. I know that we won't be able to use all the showers simultaneously, but I'd like to be able to use any two at once.

 

I can see a few solutions but maybe there's one I'm not aware of:

1. Use 15mm instead of 22mm from where the pipe branches off near the front door to the back of the house to serve the kitchen and ensuite 2. This would lessen the delay overall, but with less more restricted flow to the back of the house, the shower would be more likely to be impacted by the kitchen tap?
2. Run two 15mm hot branches (or one 15mm and one 12mm) from the 22mm running along the front of the house to the back of the house. the 15mm just to the shower in ensuite 2 and the 15mm/12mm to the kitchen tap and ensuite 2 basin. This might isolate the shower from the sink more effectively and reduce delay for hot water to the kitchen/ensuite sinks.
3. A second small hot water tank with an immersion under the sink to feed the kitchen hot tap and the hot tap in the shower room and run 15mm from the front just for the shower in ensuite 2. This would decouple the kitchen from the ensuite shower and mean close to instant hot water at the taps in the kitchen and ensuite.
4. I've seen the heat geek mini store and wondered if I could put that in a corner kitchen cabinet in addition to the main DHW cylinder in the plant room. The mini store could run the kitchen and the ensuite shower/taps. I've no idea if this is even possible - planning to put in an ASHP as part of the building work and don't know if/how it's possible to run two cylinders on opposite sides of the house in parallel from one ASHP.

 

i know I have a tendency to overcomplicate things, but unfortunately that's just the way my brain works - I'm thinking through all the options at the moment. Any feedback?

[ProDave]

No 1.  MOVE the HW cylinder to a much more central position. NOW is the chance to do that. Under the stairs would be about as central as it gets in that plan.

 

No 2, don't route pipes around the edge of rooms, take the most direct straight route possible.

[Conor]

1. You don't need to use 22mm pipe at all. 15mm is fine for a shower.

2. Direct pipe routes.

3. Use 10mm pipe for basins.

4. You're over complicating it.

5. One pipe per fixture. No joins.

[JohnMo]

Run 15mm to central location and install a manifold. Then from there run a 15mm pipe to each wet room and branch the pipe there.

 

At you furthest or most used wet room add a secondary return loop. The return pipe will go directly back to cylinder.

 

The above will pre heat manifold and supply hot water to furthest or most use taps, while also allowing a shorter run to all other rooms.

 

Above will easily supply a couple of showers.

[Johnnyt]

Secondary return for me with the pump plugged into a smart plug.

Set schedules or just tell smart speaker to run the pump for 2 minutes as we do.

No excessive heat loss and hot water at furthest outlet and others more or less on demand.