Service trenches

[Vijay]

Looking at what I need in terms of service trenches - are they different depending where I live?

 

I'm looking at gas, water, electricity, phone and an extra one (or 2) for lighting/gates/security etc.) Would that cover it?

 

Would they all need to be ducted or can any be just run in a trench? Also can any share a duct/trench and what depths would they need to be?

 

I'm sure I read on older posts that some service providers supplied free ducting, does anyone know if any do?

 

Cheers

 

Vijay

[Onoff]

Find out who your DNO is or water, telecoms etc provider. A pretty detailed PDF will be on their web site ref service trench requirements.

 

Something like this:

 

http://www.swanage.gov.uk/userfiles/file/Documents prepared by Kehr and Tucker/Mains Trenching Guide Colour 2012.pdf

Edited April 21, 2017 by Onoff

[Jeremy Harris]

At home I have a copy of the PDF from our DNO, that covered the trench section detail for all the services, with differing profiles for trenches under roads or public paths to those under gardens.  They vary slightly from one region to another, though, so it's worth getting the definitive one for your region.

[Crofter]

I found these details surprisingly hard to pin down, and the best approach was to actually phone the guys who were going to do the job(s).

If you have a groundworks contractor they will probably be able to keep you right.

Safest approach is to dig it deep enough for the water, that has to be deepest for frost protection (up here anyway- might be different down south)- from memory this was 700mm. Electric shouldn't need ducted unless it is going under a road or close to the surface. I had to lay a bit of ducting where it went under my driveway and initially the guys were not happy about using a duct that they hadn't themselves laid. Their fears were partly justified as we had a right job getting the cable through- I guess a stone might have partly crushed the duct at some point. I don't know how close I came to them calling it off and wanting the whole thing dug up again, which would have been pretty annoying seeing as there wasn't a machine on site at the time.

[Vijay]

Cheers guys. It makes sense for me to call all the service providers and double check before I start. The PDF link is a great starting help though

[Jeremy Harris]

The link that @Onoff has posted is exactly the same as the PDF I got from SSE when I applied to shift some cables underground.

[Vijay]

Cheers JSHarris, would be great if they all worked to the same thing

[Onoff]

I was looking for a specific UK Power Networks document that I've posted up before.....I think, but couldn't find it. We've discussed this one before though:

 

https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://www.njug.org.uk/wp-content/uploads/V1-Positioning-Colour-Coding-Issue-8.pdf&ved=0ahUKEwjrnI-G6rfTAhVRbFAKHa0ICoMQFghgMAg&usg=AFQjCNFhzY5fDIDEo-f-Sz3OF0NYGinxqg

[Vijay]

That looks to me more for public highways though, would the same apply to residential?

[Onoff]

9 minutes ago, Vijay said:

That looks to me more for public highways though, would the same apply to residential?

 

The depths apply I'm sure. Pick the bones out of this for lateral spacings:

https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://www2.nationalgrid.com/UK/Services/Gas-distribution-connections/Documents/Pre-excavation-and-Ducting-Guide-effective-from-01st-October-2016/&ved=0ahUKEwjzncCypbjTAhXMZlAKHbflD-AQFggaMAA&usg=AFQjCNE11ML0-JY9tI-Fb0Nuc2V1E1OQDQ

 

[Vijay]

What extra ducting did you guys fit? Did you bother with a specific colour for it?

 

Also, is it right to use perforated gas pipe? Where would unperforated be used?

 

Trying to get an answer out of the service providers has been like pulling teeth

[ProDave]

Black duct for electricity (some DNO's want red), grey for BT, water buried direct.

[Vijay]

Sorry, I should have made myself clearer, I meant colours for the extra/spare ducting

 

Does the ducting need to buried in shingle like drainage or is it just buried in the ground/clay??

[Crofter]

Inwould just go for black for any extra ducting, that way the worst that will happen is that someone who hits it with a digger assumes it's electric and tries not to break it. And it should allow you to run electricity down it later without worry.

 

I was told to backfill using anything that wouldn't damage/crush the duct. In theory you can just grade the soil that came out of the trench (remove larger/sharp stones) but in practise it's easier to convince the service people if you buy in some sand or dust. A lot quicker too!

[Vijay]

would 10mm shingle do as I have a bit left over from doing the drainage?  Does anything need to go under the ducting??

[Peter M]

It would appear from what I am reading is that different DNO's have different requirements, what I am unable to find out however is what provision should be made in relation to the electricity supply cable actually entering the shell of the house and then eventually ending up in the electric meter box, my existing property looks as if it is in the cavity coming up from somewhere in the foundations but as this house is yonks years old I can only assume that things have moved on and some regulation or other exists out there that we self builders must adhere to.

Another rub is that all the external meter boxes out there seem to be white GRP or plastic, yuck, especially as we will be having dark slate grey cladding, is it OK to have the box sprayed a matching RAL colour to match the exterior finish or is that against the rules!!

Any thoughts or ideas would be appreciated.

[le-cerveau]

If you have an external meter box the supply does not enter the house but is external and what goes into the house is done by your electrician.  YOu underground duct, as required to the meter box, teh DNO fit their gear, your supplier fits the meter, then your electrician fits remainder. (Over simplification and an expert will be along).  You can go internal (I managed, but my supply is 3-phase).

 

DOn't know about spraying the box though!

[Peter M]

Cheers appreciate the reply, as were having cladding where the meter box will be installed and not wanting the box to project to far out from the blockwork I'm guessing that the supply cable will be routed on the surface of the blockwork & behind the cladding before it enters the meter box, from there, after the main supply meter there will be 10mm tails to the consumer unit? is this correct? also should any of this cabling be ducted or chased into the internal masonry??

[le-cerveau]

3 hours ago, Peter M said:

after the main supply meter there will be 10mm tails to the consumer unit? is this correct? also should any of this cabling be ducted or chased into the internal masonry??

 

This is the limit of my knowledge, the tails from the meter to your Consumer Unit need to be less than 2m (I think) otherwise you need an isolator (I have on as it is a long run from my Metre to CU).

 

As for ducting/chasing in I think a lot of that is personal., but if ducted there are rules.

[TerryE]

9 minutes ago, le-cerveau said:

This is the limit of my knowledge, the tails from the meter to your Consumer Unit need to be less than 2m (I think) otherwise you need an isolator (I have on as it is a long run from my Metre to CU).

 

This is what my Spakie said, but he also said that the regs didn't specify where between the CU and the meter this had to be positioned, so we have ours next to the meter on the same board. but he also ran SWA from the CU to the isolator.  I had to put the ducting pipe through the TF at 45° or we wouldn't have been able to make the turn within the service cavity depth.

Edited March 28, 2018 by TerryE

[le-cerveau]

4 minutes ago, TerryE said:

so we have ours next to the meter on the same board.

 

Same for us, 3 phase isolator above the meter, massive box with a 90 degree turn handle, up the garage wall into the ground floor ceiling void, 10m along the hall and up into the plant room for the CU.