Long length of 28mm pipe in floor

[cwr]

Hi folks

For the return pipe for our boiler stove I plan to run it in the floor insulation (floor build up: 50mm liquid screed over 170mm PIR over slab). Problem is I need about 3.5m run, so a 5m length of pipe is required. I really don't want a joint in the floor, tho there is a possibility i could put in a void in the screed to  access at one discrete point.

Can you get copper pipe 5m long?Any other thoughts?

Thanks

[Temp]

You can buy 6m lengths of 28mm copper pipe but how readily available they are I'm not sure. A few Google finds..

 

https://www.wolseley.co.uk/product/the-lawton-tube-en-1057-x-copper-tube-28mm-x-6mtr/

https://www.plumbparts.co.uk/product/copper-pipe-coil-28mm/

https://www.palmer.uk.com/Product/1598/Copper-Tube-6m-Lengths

https://www.abcoplumbingfittings.com/copper-tube/

 

[Nickfromwales]

Just solder the joint and move on with your life  I've done thousands of soldered joints, water / gas etc and it's perfectly fine. You're waaaaayyyyy over-thinking this.

Solder it up, pressure test it at mains for 24 hours, and get it in the ground. 

[TerryE]

I know the professionals like Nick make it look easy, but just about anyone who is modestly handy can do this   So if you aren't familiar with soldering, then just buy 28mm ring-fills.  You can dry fit and cut the pipe to length, then joint the pieces conveniently positioned out-of-place. Look at some YouTube demos of soldering ring fill joints.

 

So long as everything has been cleaned to virgin bright copper and fluxed, and the area is clear of contacts / cold spots then you can heat the pipe uniformly and let the heat flow into the joint. Once the ring of solder wicks out under heat completely around the ring, then you know that the joint is sound. Clean. Ditto any end 90 elbows that are in-slab  And remember that any piping in-slab must be decently lagged both for thermal reasons and to ensure that the concrete does not come into contact with the copper.

Edited May 11, 2022 by TerryE

[MikeSharp01]

@cwrWhy not use a length of 28mm plastic pipe you can just uncoil it, I used wall paper stripper to fill the pipe with steam and straighten it, then you can be sure of no joints at all you cannot get to and you do not need to master soldering or fret about failures. 

[Nickfromwales]

28 minutes ago, MikeSharp01 said:

@cwrWhy not use a length of 28mm plastic pipe you can just uncoil it, I used wall paper stripper to fill the pipe with steam and straighten it, then you can be sure of no joints at all you cannot get to and you do not need to master soldering or fret about failures. 

Hepworth do a 6m length in a straight run. LINK

People have been soldering pipes longer than they have been pushing fittings onto plastic pipes  I've been plumbing for nearly 30 years, and I would use copper in this instance over plastic for sure.

[cwr]

Is it ok to have plastic pipe right up to the boiler? I should have mentioned that one end comes up right behind it. I was under the impression that you should have the first meter in copper.

[Nickfromwales]

1 minute ago, cwr said:

Is it ok to have plastic pipe right up to the boiler? I should have mentioned that one end comes up right behind it. I was under the impression that you should have the first meter in copper.

Some manufacturers say the first 800mm - 1000mm in copper, in case the boiler overheats and sends super-high temp water out for a few seconds. Plastic pipe and fittings have very low pressure ratings at very high water temps.

[Nickfromwales]

7 hours ago, Temp said:

I'm not sure

Pipeline Centre should carry stock. This is the best option here, but the OP would still have soldered joints to make at each end. 

 

@cwr, you could get a 6m length and have a commercial plumber form a mechanical bend at each end if this is really keeping you up at night. You seriously will be fine with a soldered joint. Any good plumber can solder this in their sleep.

[cwr]

Thanks for the replies folks.

I'm perfectly happy making solder joints, but just like the idea of any joint being accessable. 

I'll put bends where the pipe has to come up, so just one joint to lengthen it if I can't find any 6m lengths locally.

[TerryE]

According to regs, compression joints in slab have to be accessible. No need for soldered joints once tested to be accessible.  They fail because of cold spots / contamination preventing solder wetting / flow and so (typically) the flux residue is acting as a temporary seal that will ultimately fail. Ring fill have already got a 360° wet on the joint. So long as the pipe is clean and fluxed, then this will also wet forming a permanent seal. Same applies for elbows bringing pipe up from slab level.

As Nick says, you can always pressure test before you pour concrete.

[HughF]

This is what mlcp was made for….. just saying’ 😂

[Hastings]

Be aware that plastic has many times higher temperature expansion coefficient than copper.

 

I learnt this from experience when plastic heating pipe was laid underground (insulated and in a 110 pipe) in a straight 10-15m run from my house to a garage office room. When hot, the pipe lengthened by about 20-30mm and caused a leak at the first 90 elbow at the garage end because the next section of pipe was fixed very firmly to a wall.  The solution was to remove one wall fixing to allow the 90 degree pipe to move away from the wall and relieve pressure on the 90 joint.

 

In Alaska where above ground oil/gas pipe lines are set on posts run alongside roads for 1000s of miles they form it into a 20m ('ish?) square 'U' shape every few kilometers to act as a sort of expansion/contraction spring.

[Carrerahill]

On 11/05/2022 at 23:57, Nickfromwales said:

Just solder the joint and move on with your life  I've done thousands of soldered joints, water / gas etc and it's perfectly fine. You're waaaaayyyyy over-thinking this.

Solder it up, pressure test it at mains for 24 hours, and get it in the ground. 

I agree with this. 

 

I always solder and always use copper, unless really not possible (or temporary).

 

I have a pushfit stop end and a test jig I made with a pressure gauge, ball valve and Schrader valve which also lets me pressurise pipe runs not yet active (I fill with water then use a compressor to blow up to test pressure - not meant to do this I know but in my own house I make the rules).

 

When I did my boxed in copper pipework in my new kitchen I left it overnight with 4bar in the pipe with the marker set on the needle, following morning the needle had not moved. I boxed them in and forgot about them. Should be good for 70-80 years unlike PVC which CIBSE lifespan tables show only to last 20-40. I also did some radiused bends and things to limit solder joints to 2 within that section.