Laying a water pipe and cable

[kianok]

I need to get power from the house to the garage and ideally a water supply too, the distance is about 40ft.

I understand that the cable has to be buried about 18 inches below the surface and inside a suitable pipe.

Can a water pipe be buried in the same way? (in a seperate protective pipe obviously). Does it need to be insultated to prevent freezing or will it be fine so long as it's far enough below the surface?

 

[dozypillock]

I need to get power from the house to the garage and ideally a water supply too, the distance is about 40ft.

I understand that the cable has to be buried about 18 inches below the surface and inside a suitable pipe.

Can a water pipe be buried in the same way? (in a seperate protective pipe obviously). Does it need to be insultated to prevent freezing or will it be fine so long as it's far enough below the surface?

When I supplied power to my outhouse at my last residence, I was advised that armoured cable was sufficient, so that was used.
Not sure about water, but suspect, as you said, that buried deep enough, it would have to be cold for a long time, or so cold you would probably not want to venture out, for it to freeze underground at that depth?

Neil

 

[nb_racing]

As per dozypillock, I questioned my sparky about doing exactly the same and he said if it's armoured you don't need to bury it. And he has his own company and has signed of all the electrics in my house so putting his reputation on it.

Don't know about water but i'll be keen to find out as I'm installing a cold feed in the spring.

 

[Giantvanman]

The water pipe should be buried deep enough so frost does't reach it. I am sure someone will come up with the building code regs.
As an aside, as a temporary measure (about ten years ago ) I placed copper pipe on a separate run from my outside tap, along between garage and house, on the ground with only that grey foam tube insulation on it. No leaks and it has never frozen. I have the bits to replace with MDPE blue mains pipe now the building work is progressing but based on the previous ten years, I won't be digging up a concrete path to lay it in the ground. I will just use the same insulation and box it in and expect no trouble.
Hope that helps.

Edit: I am not suggesting this is the correct way, just saying that I don't think it as critical as one would think.

 

[camerafodder]

There's no regulation depth as such for armoured cable. However if burying it should be deep enough to prevent accidental digging damage. For that reason I would either bury it at least 300mm below the water pipe if using the same trench (in case you have to dig up the water pipe for repair) or more preferably in a different trench spaced well away from the pipe trench. As a good rule of thumb cable should be 2 spade depths from the surface and bedded on sand with sand above before backfilling. Use armoured cable and direct bury. You can also buy warning ribbon to bury nearer the surface that will quickly warn anyone that starts digging well before they hit a cable.

 

[KennyN]

I ran my 4mm sq. armoured cable through a piece of conduit 12" below the surface. The supply is taken directly from the RCD side of the house consumer unit and fed into a mini unit in the garage that contains two breakers , one for the double sockets (x6) and one for the strip lighting (x5)

Kenny

 

[Piff]

Normal proceedure for new houses:-
Blue alkathene for water 750mm deep, to one side of trench.
Part back fill trench to 450mm deep & lay electric on the other side of the trench, either armoured or in black duct. Back fill a further 100 - 150mm & lay warning tape over electric cable then compleate back filling

 

[johns E350]

You do not need to put SWA cable in a duct. Here is one for anyone who knows the electrical regulations If your incoming supply is PME TNCS then consideration should be given as to making the garage a TT system if it is that distance from your house as it is outside the equipotential zone. This is because if the suppliers neutral is lost the installation will become live. I could go on, if you use a 3 core SWA cable which will be Brown Black and Grey you must use the Black as Earth and the Grey as neutral also even if you are not using the armour as an earth it must still be earthed at one end that is if it is not going to be a TT system Anything you want to know about BS7671 feel free to ask as I work in conjunction with the NICEIC I could go on about the need for a 100ma RCD etc etc

 

[kianok]

Thanks for the replies.

Father inlaw is an electrician so he can do the technical / building regs stuff.

I'll just be digging a long hole!

 

[bolide]

You do not need to put SWA cable in a duct. Here is one for anyone who knows the electrical regulations If your incoming supply is PME TNCS then consideration should be given as to making the garage a TT system if it is that distance from your house as it is outside the equipotential zone. This is because if the suppliers neutral is lost the installation will become live. I could go on, if you use a 3 core SWA cable which will be Brown Black and Grey you must use the Black as Earth and the Grey as neutral also even if you are not using the armour as an earth it must still be earthed at one end that is if it is not going to be a TT system Anything you want to know about BS7671 feel free to ask as I work in conjunction with the NICEIC I could go on about the need for a 100ma RCD etc etc

Lots in here that I don't understand so I did a bit of Googling. Looks like it's all about safety, earthing and protecting circuits by various means. A point I hadn't thought of is what happens if the garage loses the earth via the supply cable due to a fault

An RCD detects a current flow to earth and trips the system. But if the local earth is lost or is bad…

Nick Froome

 

[dan-mb]

Using a narrow trenching shovel dig a 500mm deep trench with 20mm pea shingle/sand above and below and infill and your good to go.
The electrics side needs a pro. How will you be making the armoured ends of? With the correctly sized glands? Will it be correctly fused, what type of earthing system does the house have? TT TNCS TNS? Especially if you are going to get it certified.

 

[kianok]

The electrics side needs a pro. How will you be making the armoured ends of? With the correctly sized glands? Will it be correctly fused, what type of earthing system does the house have? TT TNCS TNS? Especially if you are going to get it certified.

My intention is to do the basic work myself and then have a family member who is an electrician to do the termination work at both ends (to regs)

The house is only a couple of years old if that answers you question regarding the earthing system?

 

[johns E350]

Lots in here that I don't understand so I did a bit of Googling. Looks like it's all about safety, earthing and protecting circuits by various means. A point I hadn't thought of is what happens if the garage loses the earth via the supply cable due to a fault An RCD detects a current flow to earth and trips the system. But if the local earth is lost or is bad… Nick Froome

That is correct but it will also notice an unbalance if you are getting a belt and will trip Remember an RCD does not stop you getting an electric shock. There is always what if but the chances are low and that is the reason for periodic testing now known as an electrical installation condition report

 

[sallison1504]

You do not need to put SWA cable in a duct. Here is one for anyone who knows the electrical regulations If your incoming supply is PME TNCS then consideration should be given as to making the garage a TT system if it is that distance from your house as it is outside the equipotential zone. This is because if the suppliers neutral is lost the installation will become live. I could go on, if you use a 3 core SWA cable which will be Brown Black and Grey you must use the Black as Earth and the Grey as neutral also even if you are not using the armour as an earth it must still be earthed at one end that is if it is not going to be a TT system Anything you want to know about BS7671 feel free to ask as I work in conjunction with the NICEIC I could go on about the need for a 100ma RCD etc etc

Could you not just use two core armoured and use the armour as an earth, by connecting that straight to the earth in the house CU? Then if the Supplier neutral was lost and there was a fault, then it would trip the RCD?

 

[johns E350]

Could you not just use two core armoured and use the armour as an earth, by connecting that straight to the earth in the house CU? Then if the Supplier neutral was lost and there was a fault, then it would trip the RCD?

You could a 2 core SWA but most consumer units are plastic so the gland would need to be made off to the plastic enclosure then then you would need to use a banjo M6 nut and bolt 6mm Earth lug earth cable from banjo to MET etc easier to use a 3 core.

if the suppliers neutral was lost the RCD would not trip as it would not have a neutral to know the imbalance

 

[kianok]

Thanks for the replies everyone, really apreciate your help

 

[sallison1504]

You could a 2 core SWA but most consumer units are plastic so the gland would need to be made off to the plastic enclosure then then you would need to use a banjo M6 nut and bolt 6mm Earth lug earth cable from banjo to MET etc easier to use a 3 core. if the suppliers neutral was lost the RCD would not trip as it would not have a neutral to know the imbalance

Ahh I see! I always assumed when the supply was lost, you'd lose the live and the neutral together, but I imagine if it was on a TT, a neutral could easily be lost if it was damaged by a tree or something. Never even thought of that before.

 

[kianok]

Thanks for all the advise on this.

We have exchanged contracts today and we move in tomorrow (it's been a stressful week!) so I want to get cracking straight away.

 

[flying haggis]

use 3 core swa directly buried, as said above use the black as earth and also earth the armouring. if you use just 2 core and trust the armouring as earth if the cable gets damaged and allows water to get to the armour and it rusts away you then dont have an earth connection

 

[Robfen100]

I did something similar a few years back:

Get cable warning tape (Scewfix sell it IIRC, pretty cheap) and lay above the cable when you backfill the trench, someone's spade will find that before a live cable!