Laying Electrics and water pipe for outbuilding

[SysMax]

I'm about to bury armoured cable, armoured ethernet cable and mdpe water pipe running from my house then under a kitchen extension, under patio and lawn to an outbuilding, total distance about 20m. The posts I've read here only seem to consider the electric cable but not the water pipe together.

I'm not too sure how deep I should lay each type of cable and what type of aggregates I should surround each type of run. I have an 80cm trench already dug. I've seen different types of options and cross section drawings on the net but I'm not clear on the best method.

I purchased the following items from TLC

SW16/3 16.0mm⊃2; 6943X 3 core SWA Steel Armoured Cable
CACAT5E/SWA CAT5e - 4pr External Steel Wired Armoured Cable
FMPT103 Electric Cable Below Tape 150mm x 365Mts

At first I going to lay the water pipe in backfilled soil at 80 cm, followed by the electric cable and ethernet cable in sand (or pea shingle?) at 45cm but slightly offset from the water pipe. Finally the warning tape.

Your kind advice would be highly appreciated, thanks in advance.

 

[chivers67]

Sand would be best so there are no sharp edges that could penetrate the insulation under pressure from weight to cause ingress and eventually degradation. 45 cm is adequate but as deep as possible/practical. Even a duct would be good.

Be interesting to see what others say

 

[SysMax]

Sand would be best so there are no sharp edges that could penetrate the insulation under pressure from weight to cause ingress and eventually degradation. 45 cm is adequate but as deep as possible/practical. Even a duct would be good.

Be interesting to see what others say

Thanks for your reply chivers67. Not many other replies lol. Looks like I will fill up to the warning tape with sand.

 

[Stewb]

I would use regular outdoor cat 6 in ducting, filling the two ends at ground level with expanding foam. I would hazard a guess that would be similar cost or cheaper than cat 6 armoured and would future proof you for new LV cables in future. Also avoids the challenge of glanding and earthing the cat 6 and the risk of leaving an earth to house in place if you TT island.

16mm2 is chunky for the supply. Presume you’ve done the sums.

Remember to also check re exporting the house’s earth to an outbuilding or if a TT island is the correct approach. Refer to your DNO for guidance on that.

Good luck!

 

[Wayners]

Water pipe should be 750mm deep so it don't freeze.

I'd run the internet cable in a hose pipe.
Water pipe don't need anything around although I'd wrap in pipe insulation.
Keep internet cable away from the electric cable Vs up against.

I had similar office in garden and run plastic heating radiator pipes in ground. About 500mm deep inside 40mm waste pipe. Put small radiator in the insulated shed.

 

[oldbutnotdead]

800mm is ok depth wise. Sand or pea shingle as a bed for the pipe and cables, once you've covered them with a couple of inches, a layer of soil is a good idea (100mm or so) then a layer of solids (bricks or blocks or bits of slab) and as many layers of marker tape as you like (I put one below the 'solid' layer, one above it and a couple about 200mm below ground level).
I'd have gone with ducting rather than a single data cable but that's up to you.
Power cable wants to be down at the bottom with the water pipe. I'd stick the data down there as well (keep power one side, water in the middle, data the other side).
Given you are going under a building (quick reread) I'd strongly advise ducting for all 3 services since digging out any failures would be a bit of a bore. Check minimum bend radius for your 16mm where it goes down/comes up. Data-wise good practise to run minimum 2 cables anywhere (again for failure redundancy).

 

[SysMax]

I would use regular outdoor cat 6 in ducting, filling the two ends at ground level with expanding foam. I would hazard a guess that would be similar cost or cheaper than cat 6 armoured and would future proof you for new LV cables in future. Also avoids the challenge of glanding and earthing the cat 6 and the risk of leaving an earth to house in place if you TT island.

16mm2 is chunky for the supply. Presume you’ve done the sums.

Remember to also check re exporting the house’s earth to an outbuilding or if a TT island is the correct approach. Refer to your DNO for guidance on that.

Good luck!

Yep done the sums close to 300 quid inc vat for 25M !!!!!! sob! Thanks for the advice.

 

[SysMax]

Water pipe should be 750mm deep so it don't freeze.

I'd run the internet cable in a hose pipe.
Water pipe don't need anything around although I'd wrap in pipe insulation.
Keep internet cable away from the electric cable Vs up against.

I had similar office in garden and run plastic heating radiator pipes in ground. About 500mm deep inside 40mm waste pipe. Put small radiator in the insulated shed.

You'd wrap the mdpe pipe in insulation at 800mm? Ok better safe than sorry. I thought about running CH to the outbuilding but declined in the end. Thanks Wayners.

 

[chivers67]

I used Cat5 Screened cable when I ran my power to our garden room and did what Wayners suggested in a hose pipe!

 

[conny]

If you had used ducting/decide to use ducting, remember to pull a draw cord through with the cables.
Any upgrade/problem in the future can be quickly sorted by pulling a fresh cable through.
Going by recent experiences at work, telecomms/data cablers seem to have an aversion for leaving one of these in after they have pulled through the cables they need. I find it amusing at their frustration when something goes wrong, and they don't have a spare pair of leads they can use, so they have to try feeding another cable in.
I had to show one guy, (admittedly he was a youngster), how to pull a cord through by using the damaged cable from the source side, and how to attach the new cable a short distance behind the old cable. This way, he got the new cable in and had a cord for any future problems.

 

[SysMax]

If you had used ducting/decide to use ducting, remember to pull a draw cord through with the cables.
Any upgrade/problem in the future can be quickly sorted by pulling a fresh cable through.
Going by recent experiences at work, telecomms/data cablers seem to have an aversion for leaving one of these in after they have pulled through the cables they need. I find it amusing at their frustration when something goes wrong, and they don't have a spare pair of leads they can use, so they have to try feeding another cable in.
I had to show one guy, (admittedly he was a youngster), how to pull a cord through by using the damaged cable from the source side, and how to attach the new cable a short distance behind the old cable. This way, he got the new cable in and had a cord for any future problems.

Great thanks Conny, so you pull a cord together with the 1st cable and leave it in, I was genuinely wondering how it was done. Easy when you know! Any special kind of cord? Nylon fishing line?

 

[SysMax]

800mm is ok depth wise. Sand or pea shingle as a bed for the pipe and cables, once you've covered them with a couple of inches, a layer of soil is a good idea (100mm or so) then a layer of solids (bricks or blocks or bits of slab) and as many layers of marker tape as you like (I put one below the 'solid' layer, one above it and a couple about 200mm below ground level).
I'd have gone with ducting rather than a single data cable but that's up to you.
Power cable wants to be down at the bottom with the water pipe. I'd stick the data down there as well (keep power one side, water in the middle, data the other side).
Given you are going under a building (quick reread) I'd strongly advise ducting for all 3 services since digging out any failures would be a bit of a bore. Check minimum bend radius for your 16mm where it goes down/comes up. Data-wise good practise to run minimum 2 cables anywhere (again for failure redundancy).

Hi oldbotnotdead, thanks a lot for your detailed reply. I was thinking if should I or should not run ducting under the extension. I will now, imagine having to kango the floor of a new kitchen extension, you're right.

 

[oldbutnotdead]

Hi oldbotnotdead, thanks a lot for your detailed reply. I was thinking if should I or should not run ducting under the extension. I will now, imagine having to kango the floor of a new kitchen extension, you're right.

I think you'll be OK with just chucking the ducts in then burying them in concrete where they cross the footings for your extension but check with your BCO . Don't be stingy with the ducts- minimum 50mm for the SWA and water pipe (assuming 25mm), could go smaller for the data but why bother, the duct price fades into the background noise with all the other costs.
Purely out of curiosity, since you are running water to this new lair have you got drainage sorted? Can't really drop sink or shower waste into a soakaway.....

 

[oldbutnotdead]

Great thanks Conny, so you pull a cord together with the 1st cable and leave it in, I was genuinely wondering how it was done. Easy when you know! Any special kind of cord? Nylon fishing line?

The ducting you buy retail generally has a thin flexible steel wire in it already for pulling through, which is handy . Tie some thin polyprop on the end of the drawline before you start- when you have your cable through you can pull the steel line back with the polyprop so its there for next time.

 

[bernardgreen]

Tie some thin polyprop on the end

when you have your cable through you can pull the steel line back with the polyprop so its there for next time

Use braided rope and NOT twisted rope. Twisted rope untwists under tension and will cause the cable and the steel line to wrap around each other thus rendering the steel line unusable as a future draw cord

What kind of conduit do I need for buried armoured cable?

What ever duct you use put a rope through it prior to burying, flexi duct comes with a draw wire, but i still prefer using that to pull a more sturdy blue nylon rope in I'm a bit paranoid about it, I'd probably put at least two in if I was doing the work personally :)

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