Running hep2O in insulation below screed?

[daunker]

I'm converting a building, concrete slab. Then dpm then 150mm PIR in two layers then ufh pipes and 50mm liquid screed.

 

The building is single storey has two bathrooms and kitchen.

 

I'm doing as much as I can myself to save costs. I have read with interest about the hep2O on here and simplicity of it (sounds great).

 

Easiest solution to me seems to run the water supply between insulation layers, probably channeling out the run, (or possibly as is 75mm insulation i could make the small portion of the top layer 25mm+50mm insulation, and run at least the cold supplies side by side. 

 

Is this the norm to run in the insulation layer below screed, seems v straightforward hopefully? I hope I wouldn't need it in conduit but maybe?

 

Then leave long tails up in broadly in the location, but certainly where the stud soleplate will go.

 

I have been inspired by here to have manifold and individual supplies for each so no intermediate joints/connections. Most on here are going round perimeters drilling timber studs but I have door ways and limited height so has to go underfloor or be incredibly circuitous and sharper angles?

 

[JohnMo]

To comply with building regs you really need the pipe in conduit. It is supposed to be replaceable.

 

We did cold under the insulation - this works well and keeps cold water cold. Hot we didn't do in the floor, but between the insulation for that should be ok.

[Andehh]

We did the feed and return to a second manifold, and some rads, within the insulation, below screed. No issues. Don't bury any joints down there though!!!!

[Nickfromwales]

1 hour ago, JohnMo said:

It is supposed to be replaceable

I was sure you just couldn't have joints buried? You'd not be pulling copper out and pulling new in?

[daunker]

Lovely thanks team great news. Exactly what I was hoping to hear. Will look up fitting and manifold instructions in due course but for now will run the five pipes per bathroom, or four I guess if the basin/toilet unit splits the feed which it may do?

[Nickfromwales]

1 hour ago, daunker said:

Lovely thanks team great news. Exactly what I was hoping to hear. Will look up fitting and manifold instructions in due course but for now will run the five pipes per bathroom, or four I guess if the basin/toilet unit splits the feed which it may do?

Split the shower cold and basin if you're going to split, as the WC will still be filling when you use the basin tap to wash your mits  

[JohnMo]

10 hours ago, daunker said:

five pipes per bathroom

We just did one hot, one cold per wet room, and the split in the room to each user. No issues at all. Can flush loo and shower temp doesn't change for example. Did each feed in 16mm. No issues filling a bath either.

 

So if you need to work on the plumbing in ensuite you just close a single hot and cold valve on manifold instead of 5. 

[Nickfromwales]

15 minutes ago, JohnMo said:

We just did one hot, one cold per wet room, and the split in the room to each user. No issues at all. Can flush loo and shower temp doesn't change for example. Did each feed in 16mm. No issues filling a bath either.

 

So if you need to work on the plumbing in ensuite you just close a single hot and cold valve on manifold instead of 5. 

Agreed, if a bigger house and you want to save on pipe work.

 

But the whole point of radial is to not have multiples of satellite T’s / connections etc, just a continuous pipe from A>B. 
 

Where are the T connectors for each room? Wall / floor / access panels? Buried and forgotten about?

 

I’ve no issue with joints btw, I’ve fitted thousand, and will continue to do so happily, just the beauty of manifolds and radial plumbing seems lost if you don’t go the whole hog, imho. 

[G and J]

24 minutes ago, JohnMo said:

We just did one hot, one cold per wet room, and the split in the room to each user. No issues at all. Can flush loo and shower temp doesn't change for example. Did each feed in 16mm. No issues filling a bath either.

 

So if you need to work on the plumbing in ensuite you just close a single hot and cold valve on manifold instead of 5. 

So a single cold water manifold that is after the pressure balancing valve serves all bathroom outlets?

 

If so thats simple, I like that.  I had assumed I’d have to have a balanced cold water manifold just for showers.  

[Nickfromwales]

23 minutes ago, G and J said:

So a single cold water manifold that is after the pressure balancing valve serves all bathroom outlets?

 

If so thats simple, I like that.  I had assumed I’d have to have a balanced cold water manifold just for showers.  

Everything after the control group is pressure balanced, and you need every single outlet fed from these, not just showers! Any mixer outlet or device where hot & cold meet each other needs to be off balanced feeds. 
 

If the kitchen sink cold is off raw hard water and the hot is via the control group then you need to fit a non return on the hot side. If your mains pressure is above 3.5-4 bar you should also fit a PRedV on the cold feed to that outlet too.

 

 

Those 3 sets of manifolds are all hots (from left to right) 2x kitchen and utility sinks @55°, then all baths / showers / basins @45°, then 3x hot returns. Cold manifold out of shot but each cold outlet and each hot outlet is on its own run there.

 

Why have cotton when you can have silk   

 

 

That’s the incoming cold main picked up for the raw hard supply to the kitchen sink, going via a PRedV and then to a 1x manifold isolator. Note I also teed off that to service the filling loop. 

[JohnMo]

Our system is slightly different as we added the UVC after. But in effect it works as you describe.  Our original was a combi boiler. We have a pressure regulator valve as the mains water comes into house. So cold water manifold after that. 

 

Early build photo attached. Showing stop cock with no mains connection. Pipes going into floor are cold, pipes going up are hot. Top left pipe is feed from combi (now UVC) the white pipe going up is the cold feed to combi boiler (now UVC).

 

But you would just feed everything from from the balanced feed.

 

[G and J]

12 hours ago, Nickfromwales said:

Everything after the control group is pressure balanced, and you need every single outlet fed from these, not just showers! Any mixer outlet or device where hot & cold meet each other needs to be off balanced feeds. 
 

If the kitchen sink cold is off raw hard water and the hot is via the control group then you need to fit a non return on the hot side. If your mains pressure is above 3.5-4 bar you should also fit a PRedV on the cold feed to that outlet too.

 

 

Those 3 sets of manifolds are all hots (from left to right) 2x kitchen and utility sinks @55°, then all baths / showers / basins @45°, then 3x hot returns. Cold manifold out of shot but each cold outlet and each hot outlet is on its own run there.

 

Why have cotton when you can have silk   

 

 

That’s the incoming cold main picked up for the raw hard supply to the kitchen sink, going via a PRedV and then to a 1x manifold isolator. Note I also teed off that to service the filling loop. 

Bloody hell.  Did Scotty sign this off?  Which manifold serves the transporter room?

 

 

[Nickfromwales]

35 minutes ago, G and J said:

Bloody hell.  Did Scotty sign this off?  Which manifold serves the transporter room?

 

 

If I told you, I’d have to kill you. 
 

Nothing personal of course 

[G and J]

Seriously though - is that for an 8 bedroom 5 reception room grand design type warehouse?

[Nickfromwales]

41 minutes ago, G and J said:

Seriously though - is that for an 8 bedroom 5 reception room grand design type warehouse?

Nope. Just some basic 'next-level' plumbing from Obi-wank Kenobi for some chap called Darth somethingorother......

[Oz07]

I didn't realise the manifold setup had to be so complicated. Last place of ours I did manifolds and just had a hot and cold one. 10mm to basins and 15mm to everything else. No non-return valve or pressure reducers etc. Tbf the pressure in that area was rubbish and the hot was fed off a combi so only had a certain flow rate anyway. 22mm soldered copper from the mains under the kitchen sink to the manifolds and boiler in plant cupboard. Kitchen tap direct off mains for cold with 15mm from manifold for hot. All seemed to work well was goos when occasionally had to turn something off at manifold quite easy.

[JohnMo]

23 minutes ago, Oz07 said:

didn't realise the manifold setup had to be so complicated

It doesn't - look at my image, that's hot, cold distribution and all UFH 

[G and J]

On 23/04/2025 at 09:40, Nickfromwales said:

That’s the incoming cold main picked up for the raw hard supply to the kitchen sink, going via a PRedV and then to a 1x manifold isolator. Note I also teed off that to service the filling loop. 

Yet more evidence that I think incredibly slowly:  Was laying awake last night thinking about plumbing, like one does.  I was thinking through the above and was wondering why the kitchen cold tap needed its own pressure reducing valve. 
 

I'm expecting to put one on the whole installation as our static pressure is well over 6bar, so I’m guessing to 2.5bar or 3bar.

 

All the mixer taps other than the kitchen will be fed from a balanced (softened) supply, but the kitchen is different.  

 

To allow the kitchen mixer tap to work correctly do I need to reduce it further just for that tap?

 

 

[Nickfromwales]

4 hours ago, G and J said:

Yet more evidence that I think incredibly slowly: Was laying awake last night thinking about plumbing, like one does. I was thinking through the above and was wondering why the kitchen cold tap needed its own pressure reducing valve.

If hot comes via the control group and the cold comes from the raw mains, and they converge at the same mixer outlet, then there is a differential there that needs addressing somehow.

 

4 hours ago, G and J said:

I'm expecting to put one on the whole installation as our static pressure is well over 6bar, so I’m guessing to 2.5bar or 3bar.

The MI's for the UVC will demand that the CG / PRedV is within close proximity (immediately off) the UVC, and this cannot be mounted remotely. If this was a retrofit then you'd have to install a second PRedV at the incoming cold mains stopcock, and still fit the CG as per, plus then you'd have to fit a single check NRV on the hot outlet of the UVC to prevent any chance of back flow (reverse pressurisation) to the UVC.

 

If you have 5-6 bar coming in then I'd preserve that all the way to the CG and enjoy better dynamic flow rates, and then look at branching off that 6bar backbone for the raw (unsoftened) cold mains; these typically go to the kitchen sink for human consumption, but also to things like a Quooker tap or fridge dispenser etc, and also the filling loop for the heating system (as you're not supposed to fill that with softened water).

 

Are you having a softener?

 

Therefore what I have done above, is drop the incoming mains supply to match the value of the PRedV in the CG so the system has no unbalanced feeds meeting at any mixer outlet, so as to prevent the backflow issue completely (even in the event of the raw PRedV failing for eg). For that job the mains is around 2.5bar or slightly over at night, so neither of the PRedV's will ever tap out, they are there for any eventuality such as the network pressure getting hiked up as the surrounding areas get massively developed with new homes.

 

4 hours ago, G and J said:

To allow the kitchen mixer tap to work correctly do I need to reduce it further just for that tap?

Yes, it'll need balancing down to the same value as the CG PRedV.

Edited 2 hours ago by Nickfromwales
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