Manifold for Potable Water - How does this design look?

[Undaunt]

I am in the process of moving a bathroom from the rear 'outrigger' of a small victorian terraced house, to a section of the front bedroom.

We are about to build the stud walls & since I plan to install a manifold setup for hot and cold water, I wanted to check what folks thought of this proposed setup?

So far the old lead main water supply pipe has been replaced with a 32mm MDPE pipe to the left of the front door. Following that there is currently :

• Philmac 32mm MDPE - 28mm Copper/PEX Adaptor
• Pegler 28mm PB300 Full Bore Lever Valve (stopcock)
  
• Pegler PX50C Brass Compression Reducing Tee 28 X 28 X 15mm (to front garden tap)
  
• Pegler PX50C Brass Compression Reducing Tee 28 X 28 X 15mm (with drain off valve)
  
• Hep2O Plastic Push-Fit Equal 90° Elbow 28mm
• 28mm pex pipe that runs between ceiling joists, to original plumbing under old combi boiler, then to bathroom & kitchen in 'outrigger'

The plan as shown in the diagram above :

• Insert Hep20 28mm Equal Tee prior to the 28mm Elbow (to allow original plumbing to remain functional for now)
• Step down to 22mm pipe to Cold Manifold (approx 4.5m run)
• Ten manifold ports for 10mm or 15mm pipe runs to the various fixtures in the parts of the house shown in the diagram
• Provision of a 22mm port in manifold for a later date after loft has been converted and ASHP installed - to run to an Unvented Cylinder (horizontal) under loft eaves
• Run 22mm pipe run for bath? (or would 15mm be sufficient? It is a going to be a large/deep OmniTub Duo filled from a wall mounted mixer tap)
• For now we will run a temporary pipe back from the Combi Boiler to the Hot Manifold
• In future the proposed input for the Hot Manifold will be via a 22mm pipe from the Unvented Cylinder in the loft
• The unvented cylinder will have some kind of pipe run (as designed by installer) to the Air Source Heat Pump installed in the front garden

Questions :

1. Which outlets will 10mm pipe be sufficient for? I am guessing cloakroom and both bathroom sinks, plus toilets will be fine. I am trying to minimise drilling of the joists (175mm thick) and simplify routing - preferably using zero hidden joints, so 10mm would be ideal due to flexibility. However I am concerned about sufficient flow.
2. Does it make sense to branch off the dishwasher from the kitchen sink, plus the washing machine from the cloakroom toilet as shown? I am guessing I would need 15mm runs for that. Would it make more sense to run 2x 10mm to kitchen and 3x 10mm to cloakroom instead? Being a small terrace there isn't a lot of room to work with!

My current proposed location of the manifolds, is in the stud wall between the bathroom and hallway as shown. I am thinking they will fit 'vertically' with the outlet pipes going sideways then curving up or down through the void to the ceilings above/below or directly into the bathroom as required. The wall is going to be thick to hide the soil pipe stack, so I envisage an insulated (PIR?) barrier between the hot and cold pipes/manifold with separate access panels for each on either side of the wall.

More images for context of the house and future layout changes below. I'd love to hear thoughts and any helpful suggestions about this proposed design.

Current Upstairs :

Future upstairs :

Current Downstairs (with proposed location of soil stack - to be hidden in internal lobby door frame) :

Future possible downstairs :

Side elevation / cutaway showing new hallway 'storage wall' :

Front of house :

 

[bernardgreen]

The bidets will need special consideration to prevent back flow contaminating your drinking water

https://www.waterregsuk.co.uk/news/...ler_news/dont_be_a_douche_about_hand_showers/

 

[Hugh Jaleak]

All the Manifolds mean over complication and a lot of extra unnecessary pipework to me, I'd take the supplies to where they need to go, they tee off as required for each appliance.

I also wouldn't be running anything smaller than 15mm or you may find you get poor flows.

Bernard has already picked up on the Bidet, this will need suitable backflow prevention to comply with Water Regs.

 

[ianmcd]

as @Hugh Jaleak says , you are way over complicating things for yourself

 

[dilalio]

Get rid of the bidet and buy a washlet.
Have you had yield projections done for your ASHP and researched noise levels for you and your neighbours?
Will it and all those long hot runs be able to prevent legionella risk?
Have you considered a secondary return?

 

[Undaunt]

The bidets will need special consideration to prevent back flow contaminating your drinking water

https://www.waterregsuk.co.uk/news/...ler_news/dont_be_a_douche_about_hand_showers/
View attachment 243812

Thankyou for this reference. I recall reading about this and it put me off since it seemed complicated & would take up a lot of space. I may have to exclude this which is a shame since it would really help one occupant avoid kidney infections.

 

[Undaunt]

All the Manifolds mean over complication and a lot of extra unnecessary pipework to me, I'd take the supplies to where they need to go, they tee off as required for each appliance.

I also wouldn't be running anything smaller than 15mm or you may find you get poor flows.

Bernard has already picked up on the Bidet, this will need suitable backflow prevention to comply with Water Regs.

Thankyou. I guess I see it as simplification in a way. Every house I have lived in with trunk/branch plumbing suffered with problems with long time for drawing off cold water from hot taps (wasted water) and large drops in flow whenever another appliance was used.

We did a basic re-plumb of this house to delete several crazy pipe runs that went in circles with a ton of excess joints which improved things substantially. Still found that the tee-off to the bathroom sink (closer to the boiler) struggled to ‘call’ water from the temperamental boiler whilst the same 15mm that continued down to the kitchen was fine.

Having heard from others with manifold system saying it was superior in their user experience (less pressure drops, speed of hot water delivery to sinks in 10mm pipe) - I was curious to try it out since it is the perfect opportunity!

Reducing the number of hidden fittings makes sense to me - when using plastic anyway. As I understand it, each fitting reduces the internal diameter of the pipe creating more friction & reduction in flow.

Discussions like this were what helped the light click on in my head that a manifold setup might actually be a solution to the poor performance of most systems I’ve encountered in UK houses (flow drop from multiple occupants, shower scalding, crazy ‘singing’ plumbing, long time for hot water delivery, hidden isolation valves difficult to find when you need them, joints behind walls and floors having slow leaks that aren’t detected for a long time causing severe damage ‘diagnosed’ as rising damp etc)
https://forum.buildhub.org.uk/topic/2681-10mm-15mm-and-22mm-pipe-use/

I was hoping the simplicity of the run (zero fittings, smooth sweeps) might counteract the smaller bore of the 10mm pipe?

 

[Undaunt]

Get rid of the bidet and buy a washlet.
Have you had yield projections done for your ASHP and researched noise levels for you and your neighbours?
Will it and all those long hot runs be able to prevent legionella risk?
Have you considered a secondary return?

A washlet isn’t suitable for the nature of the medical condition (also why a bidet wouldn’t be installed). A ‘shower head’ is needed to carefully wash ‘downwards’ whilst sat on toilet in the right direction for prevention of utis. Looks like building regs means that won’t be possible given space constraints & requirement if air-gap / cistern setup.

The ASHP is down the line due to cost. Planning has been approved for it in front garden with specific low noise model with plants around to diffuse the sound as well.

Unsure about yield projections, but we are aiming towards passivehaus standards of air tightness as a retrofit using slightly different approach (biodegradable & truly vapour permeable material rather than plastic membranes and PIR everywhere)

Those measurements & calculations will be done in due course once we have insulated the house properly to be sure the ASHP makes sense.

 

[bernardgreen]

with plants around to diffuse the sound as well.

and maybe affect the free flow of air into the ASHP's heat exchanger ?

 

[dilalio]

and maybe affect the free flow of air into the ASHP's heat exchanger ?

As well as the plants getting freeze dried!

 

[dilalio]

Those measurements & calculations will be done in due course once we have insulated the house properly to be sure the ASHP makes sense.

Calculations need to be done now, to inform you how much insulation is required, and where, to ensure the HP will perform.
Get the heat loss of the property down as much as you can which will reduce flow temps, ensuring a successful HP conversion.

 

[Undaunt]

Calculations need to be done now, to inform you how much insulation is required, and where, to ensure the HP will perform.
Get the heat loss of the property down as much as you can which will reduce flow temps, ensuring a successful HP conversion.

We have done some heat loss calculations already which has informed my design which is relatively experimental (a contiguous Hempcrete skin around the entire property to eliminate junctions of different materials) A standard assessment of the property would be misleading at present (we removed the loft insulation got works to be done - there is ‘double glazing’ but so poorly installed that there are gaps everywhere etc)

Just for context, we are part of a group of people who are highly involved in researching how properties perform under various conditions, solving building pathologies and working out the building physics stuff around thermal conductivity, moisture management, internal weather, the differences between modelled calculations and real-world performance etc (it’s an evolving science)

 

[dilalio]

Just for context, we are part of a group of people who are highly involved in researching how properties perform under various conditions, solving building pathologies and working out the building physics stuff around thermal conductivity, moisture management, internal weather, the differences between modelled calculations and real-world performance etc (it’s an evolving science)

Well that's good. You'll know a fair bit about U values and emitter sizing which will help you achieve what you're after

Check out Heat Geeks. I'm one of them.

 

[Undaunt]

and maybe affect the free flow of air into the ASHP's heat exchanger ?

This has been considered. Unfortunately there aren’t many other options for placement to avoid this problem (it’s a small Victorian terrace close to boundaries on all sides) Ideally we would not be installing another gas boiler at this point given the government objective to ban gas boilers in the not-too-distant future.

As well as the plants getting freeze dried!

This is true & we will have to experiment to test which plants will cope with the extremes of temperature. If nothing can, an alternative diffusion will be found. Having seen an installation nearby however, I doubt the ASHP will be too problematic noise-wise. We are right next to a motorway for starters