Cable in concrete slab

[Apache]

Redoing a conservatory. Want to move washing machine to a new stud wall. Neatest way will be a trench in the concrete slab for water and electric.

How deep does that need to be? Foot traffic only, will have commercial vinyl floor glued on top. Can water and electric share a trench - if so how much of a gap? (hot/cold/power). 3 separate conduits.

Can I use this conduit for electric AND water or is electrical conduit different

https://www.screwfix.com/p/jg-speedfit-conduit-pipe-15mm-x-25m/72840

Will be an electrician who connects up if he can come when I want, otherwise it will be me!

 

[Sharpend]

Usually for electric in concrete I’d use some plastic conduit - the solid stuff, as for water pipe I’m guessing that if it’s JG conduit then it must be acceptable for their flexible pipe, not sure if it would need any additional insulation. :C  

 

[binky]

the depth will no doubt sporn an argument, but in my opinion about 6" is plenty. ie deep enough to get a decent layer of cement over the conduit. For the electrical conduit I would probably use armoured copex dependent on the cable size - do insert a drawstring or insert cable before laying in the floor. The armouring being to ensure it doesn't crush under the weight of cement. The pipes will work best in there own insulated conduit, or plastic piping, and seeing as both will be in different conduits, spacing is irrelevant. Not sure I would really want to put plastic pipes direct into cement, they will fail eventually, hopefully in about 30 years time! 

 

[Apache]

The run for the water is about 2.5m so I will take a single 3m length of copper and bend both ends up, cover in plastic conduit and concrete in.

I was thinking 4 inches, but I guess I could go to 6. I'll run cable and draw rope first. I'll know where they are and plan to be there long term. Will make sure builder knows when putting up the stud wall. Beyond that if someone puts a nail through in 20 years time I really don't care!

 

[Sharpend]

You’d be ok with 4” probably only need 3” screed over the top, it will be plenty. If you use copper pipe it has to be lagged with the correct insulation as the cement will react to the copper and corrode it pretty quick, I had this happen in a bungalow I lived in which was about 6yrs old when pipe leaked under floor due to poor lagging. With copper pipe you also have to be aware of heat transfer.  

The concrete will not crush the plastic pipe, at work the floors are laid with a 3” concrete screed directly over plastic conduit without any ill effects. 

 

[Evans Electric]

I've done conservatories with PVC conduit , the proper solid stuff ,  buy yourself a bending spring  then bush & coupler  it into a KO box .   Assuming its a socket .  

As Sharpie says with the copper pipe ,   tape it really well with the proper tape  or it'll be leaking in two years , seen it happen .   Are they heating pipes  to a rad?    Might get away with some 10mm pipe  PVC covered.  

The last few conservatories we dropped the socket cable into the cavity of the dwarf wall  & let a deep KO box into the brickwork . 

Years ago we'd have used black enamel steel conduit in screed  but no one sells it now.   We were told not to use galvo in concrete or screed  as it reacts with ....lime I guess .  

 

[Tony S]

Don’t use copper pipe in the concrete even taped over. The first place it will fail is where the pipe emerges from the slab. (It makes a beautiful job of it, looks like a pipe cutter has been used.) Polyethylene pipe is inert so won’t deteriorate due to the lime content of the concrete.

 

[Evans Electric]

Just the standard  PVC plumbing pipe then  , with the compression fittings ?  

 

[Sharpend]

Usually you’d use the long coil of pipe so that you have no joins in concrete. As we know a join is a weak point as its subject to failure. This way all joins are above ground. 

 

[Geoff1946]

There is a pipe commonly referred to as barrier pipe which is specifically designed for burial in concrete. It's used for wet underfloor heating systems. I helped my son install some of this and it seemed REALLY tough.

It was made in several laminated layers, with an OD of 16mm, which makes me think it originates on the continent. The 16mm fittings were readily available from the same source as the pipe, (i.e. an underfloor heating specialist.  I checked the specification and it is OK for potable water.

 

[Evans Electric]

I checked the specification and it is OK for potable water.

Whats potable water  Geoff ?

 

[Sharpend]

Whats potable water  Geoff ?

https://en.m.wikipedia.org/wiki/Drinking_water

 

[Evans Electric]

Never heard that term before  . :C   

 

[Geoff1946]

Sorry, I thought it was a generally known term.   As above = OK for human consumption/food preparation.

I've since noted there are differing types of "barrier pipe".   It applied to  the one we had;  I can't guarantee it applies to all.

 

[binky]

Never heard that term before  . :C   

it's a term not used much anymore, like to perambulate! 

 

[Evans Electric]

I'm familiar with that ,but   theres always something you've never come across no matter how ancient you may be .  I'd guess thats where the word "Pram"  comes from. 

Following the New York Twin Towers attack  I began to hear the term  ..." Ground Zero"   ...never heard that before  9/11   .

 

[Risteard]

Don’t use copper pipe in the concrete even taped over. The first place it will fail is where the pipe emerges from the slab. (It makes a beautiful job of it, looks like a pipe cutter has been used.) Polyethylene pipe is inert so won’t deteriorate due to the lime content of the concrete.

Qual-PEX pipe is XLPE I'm pretty sure. It's used a lot here by plumbers often with bits of copper coming up through the floor.

 

[Apache]

I was planning on using a single length of copper pipe INSIDE the plumbing conduit I linked. No concrete in contact with concrete. Maybe I have misunderstood the concept of plumbing conduit.

 

[binky]

I was planning on using a single length of copper pipe INSIDE the plumbing conduit I linked. No concrete in contact with concrete. Maybe I have misunderstood the concept of plumbing conduit.

that should work

 

[Evans Electric]

I was planning on using a single length of copper pipe INSIDE the plumbing conduit I linked. No concrete in contact with concrete. Maybe I have misunderstood the concept of plumbing conduit.

I've not seen that done TBH  .  As said above ,  I'd say PVC is the way to go . 

The other method I've seen with conservatories was while our cable went in the cavity of the dwarf wall , a small duct was cast in the concrete to take the two heating pipes  which were lagged .