Is a satellite manifold a crazy idea?

[alfaTom]

Our build is coming along nicely and I'm getting to the stage where I lie awake for hours thinking about pipes.

 

I've read plenty of topics on here about radial manifolds to reduce amount of water that needs drawing off for hot supply, plus also hot return circuits.

I kinda want both, purely because I want the water to be hot quickly and I don't want to put in one solution and find it's not enough later.

 

My problem is I don't think I could get an HRC on each radial leg without going totally overboard, so I'm thinking about satellite manifolds instead.

I can put them in fairly easy-access locations in bathrooms so joints/leaks are less of a concern, plus I can run the HRC off the end of the satellite manifold back to the UVC.

 

Is a satellite setup with HRC a wise idea? I can't see why having one manifold fed by a 22mm supply vs a few manifolds off a 22mm supply would be any different but I am not a plumber, just a hep20 enthusiast😂

 

A UVC will supply DHW, and the mains is being replaced from 15mm copper to 32mm MDPE, which means I don't know the mains pressure yet. I do know the HPPE was replaced in recent history so I am hoping the communication pipe is at least 25mm. (Keeping 32mm as cost difference is tiny and would rather not dig it up again later if water pressure drops in the area over time...) 

 

Picture for attention: I'm aware I'm missing lots of parts but as a "map" of what we're after hopefully it helps.

 

The run to the family bath section will probably be 7-8 metres, but a big steel to support the opening stops me running all the individual pipes through and I'm looking for a "less is more" approach.

The run to the master ensuite may be closer to 12-14 metres so would benefit from an HRC I think.

Kitchen and the W/C is about 2 metres from UVC, and the utility about 4 metres.

 

Layout of house (X is hot water point downstairs, triangle is hot water point upstairs)

 

Thoughts?

[Temp]

I haven't looked at your plans in detail but we used two remote manifolds. We wanted very high flow rate showers and ran 28mm from our thermal store to a home made manifold near each of the main bathrooms. Then 22mm from there to the showers. 

 

Regarding return loop pipes..  think about hot taps where you want hot water to appear quickly and run the return from as close to those as possible. We have a basin in a WC and the return pipe connects about 8ft away from the tap. Even that's too far away from the tap. You've washed your hands before the hot comes out. The return on the kitchen tap is right under the sink at that's much better. 

 

Some people put PIR sensors in remote WC so the loop pump starts when they enter rather than running all the time. You can also put timers on them so they don't run at night if you want

 

Builders don't insulate hot pipes and the return nearly well enough or even at all in some places. Consider taller stand offs to space pipes away from walls/floors a bit further than normal so you can get more insulation around them? 

[JohnMo]

We have a long thin house and from UVC to shower is about 15m. It's run to an intermediate manifold about 7.5m each way (UVC - manifold - shower) running the shower tonight with HWC pump off (for 12 hrs) it took just over the time to take my clothes off to be hot. 15mm pipe everywhere.

 

Sorry you have had way too much time thinking. Simplify, one hot manifold, one cold, you only need one feed to each room then branch from there. 

 

Keep 22mm well away from hot water supplies other you will get bored waiting for hot water.

 

We have HWC it goes to the furthest room and through the manifold back to the cylinder. Run it on timer and thermostat.

[Kelvin]

The Rehau ‘smart’ manifold system standard install is to fit the manifolds in the room where you need the water but that’s a lot of manifolds and all the required fittings plus you need make them accessible. Our plant room is in the middle of the house with relatively short runs to the bathrooms kitchen and utility room so we have two of their 9 outlet manifolds (4 hot 5 cold in each) Very compact so take up little space. 

 

Like @JohnMo our showers are hot by the time you’re ready to get into them. 15mm pipe. 

[alfaTom]

Some good replies here - thanks everyone!

Sounds like a satellite/remote/sub manifold will work for my situation, just need to KISS.

 

  On 28/11/2024 at 21:09, JohnMo said:

Sorry you have had way too much time thinking. Simplify, one hot manifold, one cold, you only need one feed to each room then branch from there. 

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A classic buildhub problem being left with too much time. This sounds similar in principle to what I'd be doing though I think. Two manifolds to "branch" in the further rooms and everything else off one local one.

 

My main concern had been trying to keep everything radial. I think 22mm to feed remote manifolds with the HRC on the manifold via PIR or timer so the larger volume of hot water in the 22mm pipe gets circulated to mitigate that issue. I already have PIRs in place to activate the LED "pee" lights so you don't get blinded at night time so that could work...

 

[Andehh]

Fine to do that with the cold.

 

Don't do it with the hot circulation route. You need the circulation route within a couple of feet from the tap.

Our main bathrooms are within 2ft and it works perfectly... Our kitchen is a out 10ft and the hot water arrives by the time you've finished washing your hands. Still a great decision though, as without it we'd be 30m + away.

 

 

[JohnMo]

  On 29/11/2024 at 22:16, alfaTom said:

Two manifolds to "branch" in the further rooms and everything else off one local one

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Not really what I was saying. By branch I mean simply tee off to the user in the wet room. So central manifold, one leg goes to bathroom, within bathroom, that single pipe tees off to shower, bath, sink etc. dump the idea of lots of local manifolds.

 

You are making issues by complex design, then making a hot water circulation system way to complex to compensate.

[Kelvin]

  On 30/11/2024 at 07:03, Andehh said:

Fine to do that with the cold.

 

Don't do it with the hot circulation route. You need the circulation route within a couple of feet from the tap.

Our main bathrooms are within 2ft and it works perfectly... Our kitchen is a out 10ft and the hot water arrives by the time you've finished washing your hands. Still a great decision though, as without it we'd be 30m + away.

 

 

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One of the things we learned during COVID on hand cleanliness (pathogens anyway rather than anything else) it’s the soap and length of time you clean (at least 20s) that cleans your hands not the temperature of the water. Consequently I’ve never bothered waiting for hot water since knowing that anywhere I go. 

[MikeGrahamT21]

  On 30/11/2024 at 09:12, Kelvin said:

One of the things we learned during COVID on hand cleanliness (pathogens anyway rather than anything else) it’s the soap and length of time you clean (at least 20s) that cleans your hands not the temperature of the water. Consequently I’ve never bothered waiting for hot water since knowing that anywhere I go. 

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temperature does have importance, during my many years of caring for my late wife and doing IV treatments at home, we were told to only ever wash hands in cold water, since warm water opens your pores which can allow any nasties to hide away, since then I’ve always washed hands with cold water

[Gone West]

  On 30/11/2024 at 10:25, MikeGrahamT21 said:

temperature does have importance, during my many years of caring for my late wife and doing IV treatments at home, we were told to only ever wash hands in cold water, since warm water opens your pores which can allow any nasties to hide away, since then I’ve always washed hands with cold water

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Back in the seventies I was told a similar thing by a chemist at work. Don't wash your hands with Swarfega, use washing up liquid and cold water so the skin pores don't open. He said Swarfega was carcinogenic in those days.

[alfaTom]

So since starting this thread back in November I've only just really looked at the plumbing again since our grant has been approved for ASHP/UVC.

 

Reading back on everything I can see there are really only two things I care about:

• Near-instant hot water when opening taps
• High-flow of water

On my quest for high flow, I opted for 22mm pipe, and then, to compensate for cold slugs and meet the hot water needs, I went for an HRC.

It's possible I'm overcomplicating things here and might need to do some tests before I make a decision. Our old 15mm copper pipe is now gone, and I have a 32mm MDPE line in its place waiting to be connected. (Terrific job to do last weekend given the cold weather by the way)

 

I realised I have no idea what my pressure or flow rate will be in the house. I'm so used to cheap, rubbish combi boilers or the aging gravity-fed system that was present beforehand that I might be trying to fix a non-existent problem.
So, the next steps are to get the pressure tested when the new pipe is connected, and then I can do a flow test off the garden tap to give me somewhere to start.

Soon as I know those details I should be able to use the pipe diameter and distance to work out time to deliver for hot water and plan from there.

 

Thanks all for your help so far, will update once I find out the pressure & flow and replan my piping!

[Nickfromwales]

  On 16/01/2025 at 20:08, alfaTom said:

On my quest for high flow, I opted for 22mm pipe

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Elaborate as to where and how many runs of it please. 

 

  On 16/01/2025 at 20:08, alfaTom said:

to compensate for cold slugs and meet the hot water needs, I went for an HRC.

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Pipe size and from / where to again, please?

[alfaTom]

  On 17/01/2025 at 00:25, Nickfromwales said:

Elaborate as to where and how many runs of it please. 

 

Pipe size and from / where to again, please?

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Sorry - I meant I had opted for that in my designs.

It's not in place yet, so my designs are still tbc.

 

It was going to be 22mm from plant room to manifold in bathroom, with 10mm HRC on PIR.

 

Once I get actual pressure/flow rates I'll then know what I actually need (and what is acceptable for the Mrs) and if I was just horribly overcomplicating everything like @JohnMo said to fix an issue that didn't exist.

 

[JohnMo]

  On 17/01/2025 at 08:16, alfaTom said:

was going to be 22mm from plant room to manifold in bathroom

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I really wouldn't go more than 15mm, you just don't need any bigger. 

[Andehh]

Insulate the pipes thoroughly!

[alfaTom]

Another month and I am back.
Water supply has been connected up by Anglian Water and I have a nice shiny 32mm supply pipe. Left the required inspection pits and details accessible for them as per instructions but they were happy to connect up and head off - so glad I dug those pits back out for them!

 

Looks like I have about 3.5bar pressure off the outside tap. If my maths is right the 45metres of MDPE should be capable of supplying up to 92l/m which should be fine for everything I want to do.

I've tried to contact a few local plumbers to discuss plans - basically pay for their time to just go through the plumbing strategy and get them to quote for UVC/HP install, unfortunately not many seem interested. As mentioned on this forum before by others, it seems like buildhubbers are still more familiar with PEX manifolds than most plumbers. If anybody knows of someone reliable in the South Lincolnshire area it'd be appreciated!
 

 

I have been reading up on some other threads on here including a recent one by @Sunil237 (thank you!) 
I think I can finally answer the question I stated at the start of this thread:
Satellite manifolds are indeed a crazy idea for my use case. I'll be running a central manifold in the plant room that has a dedicated feed to each bathroom and tee off from that. I'll be redoing my diagrams soon so there are some iterations of the progress.

 

Cold feeds to each room will be in 22mm, hot feeds will be 15mm. I thought about running hot feeds in 22mm with an HRC setup but I think I might just be trying to solve a problem that doesn't exist - surely it'd be simpler to run a 10mm alongside the 15mm if I wanted a faster hot delivery to a basin 10metres away; that'd be 320ml of water drawoff based on my GCSE maths...

Thanks all for your help (and patience) so far!

[Sunil237]

Glad my post came in useful, unfortunately I can't give any experience based insight as I've not lived with my system yet!

 

I think you're making the right choice with the 15mm hot feed. I just didn't have the will left to argue with the plumber. 

 

 

[JohnMo]

  On 26/02/2025 at 21:09, alfaTom said:

Cold feeds to each room will be in 22mm, hot feeds will be 15mm. I thought about running hot feeds in 22mm with an HRC setup but I think I might just be trying to solve a problem that doesn't exist - surely it'd be simpler to run a 10mm alongside the 15mm if I wanted a faster hot delivery to a basin

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Just zero point running 22mm cold to each room. Do it 15mm, it is more an adequate.

 

Why would you need 22mm hot anywhere? As the crow flies our ensuite is 15m from the UVC. If I switch the shower on (with hot water circulation off) by the time I am undressed the shower water is coming out warm, another 10 secs it hot. All 15mm plastic pipe.

 

15mm hot or cold to high flow shower or bath is fine. 10mm to sink if you want to run additional pipe to bathroom.

  On 26/02/2025 at 21:09, alfaTom said:

92l/m which should be fine for everything I want to do

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That is a bonkers flow rate, why would you even need half that?

[JohnMo]

  On 26/02/2025 at 21:09, alfaTom said:

basically pay for their time to just go through the plumbing strategy and get them to quote for UVC/HP install, unfortunately not many seem interested. As

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Think you may be confusing them, they input to a strategy, they ultimately take responsibility for a design they don't understand. Basics of heat pump install and UVC is simple especially if connected to UFH.

 

You maybe simpler, to draw up design pipe sizes from A to B etc, and say you want a plumber to implement.

 

Buy all the odd stuff like manifolds your self.

 

I would start a new thread or two, one for your plumbing design (cold and hot water) another for heat pump. Draw up your base plan for each and get it reviewed and commented on.