SWA and waste pipes sharing same trench

[Sparkly]

Hi

We are laying 16mm2 two core SWA to our new log cabin which we are going to be living in for a while while we finish renovating our house. We have calculated the size of the cable based on voltage drop over the distance and usage (shower, heater, cooker etc) and are using internal rated glands, piranha nuts to terminate inside the log cabin.

We will be laying the SWA cable due to having a digger on site before we find a part P electrician to connect it inside the house and log cabin.

We are currently having trenches dug for our foul waste pipes and would like to put the SWA in the same trench. Our question is - is this ok?

We have read that Eon insist on special trunking for supply cables (looking into as need to move our supply) and they must be at least 300mm from any waste/water pipes.

If we are laying SWA directly in the same trench with the waste pipes without trunking etc do we need to separate them by at least 300mm? Should we be putting the SWA in trunking (thought the point of having swa was it did not need trunking??)?

Also what happens where the SWA cable crosses the waste pipes?

Any advice would be great

Sparkly

 

[Steve]

Thats EON's rules for their cables. You are laying a private cable - it has to conform to the electrical regs, not Eon's rules. If you're worried about it, dig the hole 300mm deeper (you know where this is going)

 

[Sparkly]

Thanks Steve for such a quick response. As you say we can go 300mm deeper but find reading through BR like swimming in treacle. Is there anything in Part P that requires this 300mm gap? (understand that Eon may just have this as part of their own rules)

 

[Steve]

not as far as i know. My uncle dug one trench when he built his garage 10 years ago, as far as i know he has power, mains water, waste, and lighting signal cables sharing the same trench.

 

[Sparkly]

Thanks Steve. Bet your uncles garage is still working fine and he did not have to worry about Part P - ah the good old days

If there are any part P electricians reading this that can give me a definitive answer that would be great

 

[ColJack]

EON want their cable duct in 300mm away from drains because the installers aren't clever enough to tell them apart and might end up trying to put the cable up the drain pipe...

 

[Sparkly]

Ta x

 

[Click-Sure]

Ever seen whats under the footpaths in residential streets when the dig them up?

300mm my a*rse!

I think the thing I would always bear in mind as far as compliance with BS 7671 is mutual detrimental effect on services, so if one of your services needed some repair work or modification in the future, would the electrical services get in your way or not, and vice-versa.

I'f you've got a mechanical digger on site (or a very eager labourer fueled up on red bull and Benson & Hedges) then I think a 300mm distance is a very good idea.

* My opinion as a Part P registered electrician