water pipes underfloor: conflicting advice: help sought.

[saveasteading]

55 minutes ago, SimonD said:

no fittings should be embedded in a floor or wall,

'Embedded' to me means locked solid in concrete or masonry. ie there could be differential stresses that could break the pipe or a joint, and cause water damage. That is sensible.

[Nickfromwales]

28 minutes ago, saveasteading said:

'Embedded' to me means locked solid in concrete or masonry. ie there could be differential stresses that could break the pipe or a joint, and cause water damage. That is sensible.

Embedded means when you cannot get to them afterwards without destruction of property (kinda thing). I could send you the regs, but it's late and I can't be arsed to write my version.

 

You'll not be turned by simple folk such as myself, so barrier it is. 

[SimonD]

8 hours ago, saveasteading said:

Hep2O say theirs comes off the coil straight, which must be good thing.

 

Yeah, pull the other one. You'll be swearing for a month of Sundays getting it straight and keeping it straight even if it is lay-flat. So you believe the marketing blurb of these but not the technical documentation for MLCP? 

 

13 hours ago, saveasteading said:

Agreed. It looks fine, but not widely stocked.

 

Well, here you you go. As it's going to be in insulation, the 9mm thickness will be absolutely fine? What diameter would you like sir?

 

16 Blue and Red 

https://www.plumbingforless.co.uk/plumbing/unipress-mlcp/unipress-mlcp-pipe/unipress-50mtr-mlcp-16mmx2.0-9mm-red

https://www.plumbingforless.co.uk/plumbing/unipress-mlcp/unipress-mlcp-pipe/unipress-50mtr-mlcp-16mmx2.0-9mm-blue

 

20 Blue and Red

https://www.plumbingforless.co.uk/plumbing/unipress-mlcp/unipress-mlcp-pipe/unipress-50mtr-mlpipe-20mmx2.0-9mm-red

https://www.plumbingforless.co.uk/plumbing/unipress-mlcp/unipress-mlcp-pipe/unipress-50mtr-mlpipe-20mmx2.0-9mm-blue

 

Oh, and here you go, Wolseley, pipe in pipe Mlcp: https://www.wolseley.co.uk/product/uponor-mlc-insulated-pipe-13mm-25-x-25mm-50mtr-blue/

And it confirms that:

 

This Uponor MLC 13mm, 2.5mm thick pipe-in-pipe is designed for integration into a building structure and can be safely covered with screed. Withdrawn without causing structural damage, this water regs compliant pipe-in-pipe is supplied in 50M lengths.

Product features

• Suitable for hot and cold and heating systems

• Suitable for recirculation hot water systems

• PE-X material construction

• Meets BS EN 13501-1

• Complies with water regulations 1999

Any decent plumbers merchant will be able to order some in from one of the multitude of manufacturers out there and the good thing is that it's often cheaper than standard plastic PEX of Polybutylene.

But hey ho, go with your barrier pipe...even if the world is moving on.

 

[saveasteading]

6 minutes ago, SimonD said:

go with your barrier pipe..

Thanks, I'll check these out.

It's not me who says to use barrier pipe... it's the others.

[saveasteading]

8 hours ago, Nickfromwales said:

Embedded means when you cannot get to them afterwards without destruction of property 

That would preclude them being threaded through studs and joists, and behind boards, fitted units....  

[SimonD]

26 minutes ago, saveasteading said:

It's not me who says to use barrier pipe... it's the others.

 

So this is what I said earlier, which you may have missed: 

 

Quote

I don't know what they're talking about regarding barrier pipe unless they're referring the plastic pipe that has an oxygen barrier as I see no need for the barrier pipe you're referring to - it's confusing.

 

First, you need to confirm exactly what barrier pipe they're referring to. Is it the MPDE barrier pipe that is design for COLD water services, or are they merely referring to Hep20 or Polybutylene push-fit pipe. As a distinction for you. PEX is the push-fit pipe that has memory and it's a pain in the arse to work with. Polybutylene is the lay-flat type of pipe that has less memory, but memory still.

 

Second, MDPE service pipes, including the barrier versions are design for cold supplier. Their specifications usually state:

 

based upon a 50
year design life at 20˚C.

 

Any
increase above 20˚C will result
in a reduction in the maximum
allowable operating pressure or
lifetime or possibly both.
Polyethylene pipe systems
should not be operated above
60˚C. 

 

Your intended purpose as I understand it is to carry domestic hot water in your kitchen. Therefore MDPE Barrier pipe is completely unsuitable for this. PEX and Polybutylene as well and MLCP (whether PEX or Pert) are tested to over 100C and are designed for hot water.

[Nickfromwales]

43 minutes ago, saveasteading said:

That would preclude them being threaded through studs and joists, and behind boards, fitted units....  

That's more or less cosmetics tbf, if considering chasing a burst pipe.  

 

Most issues are with failed joints. 99.9% of failures there are installer error, the other down to a bad o-ring or similar manufacturing defect. This is the joy of radial plumbing, as the dozens of buried (enclosed) joints is near zero.

[saveasteading]

54 minutes ago, Nickfromwales said:

considering chasing a burst pipe.  

Yes I assume this is the concern. I can't see much chance of a failure if the pipes have no joints where they run under the floor. And the insulation provides a slip layer and cover.

And at worst, it is not structure but tiles over thin screed over pir.

 

I can see why it's a pig to install whatever we do, and why heat loss will be low on some people's concern list. Not much chance of removing the island though: it is decided at a higher level.... and they do like the idea of cold being cold, and hot being hot.

 

For my interest... hypothetically, if 2 uninsulated pipes were in a duct and one had to be replaced... could they be pulled out and new ones dragged through?

[Nickfromwales]

18 minutes ago, saveasteading said:

Yes I assume this is the concern. I can't see much chance of a failure if the pipes have no joints where they run under the floor. And the insulation provides a slip layer and cover.

And at worst, it is not structure but tiles over thin screed over pir.

 

I can see why it's a pig to install whatever we do, and why heat loss will be low on some people's concern list. Not much chance of removing the island though: it is decided at a higher level.... and they do like the idea of cold being cold, and hot being hot.

 

For my interest... hypothetically, if 2 uninsulated pipes were in a duct and one had to be replaced... could they be pulled out and new ones dragged through?

If they're not going through stupidly acute bends then yes, but you'd probably have to pull both out and feed both back in again unless its a big duct.

 

They'll not need changing out in our lifetimes.......

 

Kinda moot if......

18 minutes ago, saveasteading said:

they do like the idea of cold being cold, and hot being hot

......as you'll need segregation and insulation?

[SimonD]

27 minutes ago, saveasteading said:

Yes I assume this is the concern. I can't see much chance of a failure if the pipes have no joints where they run under the floor. And the insulation provides a slip layer and cover.

And at worst, it is not structure but tiles over thin screed over pir.

 

I can see why it's a pig to install whatever we do, and why heat loss will be low on some people's concern list. Not much chance of removing the island though: it is decided at a higher level.... and they do like the idea of cold being cold, and hot being hot.

 

For my interest... hypothetically, if 2 uninsulated pipes were in a duct and one had to be replaced... could they be pulled out and new ones dragged through?

 

Here are the regs. Really you need them ducted - you are after perfection after all 😉

 

[-rick-]

So everything leading towards pipe in pipe sandwiched at the join between eps and pir (likely chased into eps).

 

so you get:

 

- pipes insulated by the eps pir sandwich

- spaced to separate hot and cold

- individually ducted for easy replacement if needed

- minimal disturbance to the insulation. Ie cutting is way less than 50mm

 

Though as @saveasteading is paying someone to do this maybe the biggest decider is what his installer is most comfortable with?