Trench for water, electricty and waste

[Molynoox]

This is the standard for under a U.K. pavement, not sure if building control would insist on this for a home building, worth asking as they’ll want to inspect the drains.

View attachment 108427

this is a good worst case scenario, but I would prefer to keep them closer together as my trench is only 500mm wide.

 

[Molynoox]

Electrical supply to the outbuilding depends upon the type of supply to the property which determines the means of earthing. Best leave this to the sparky doing the design and install.

yes I have an electrician to do all that stuff, I have no clue.

 

[Molynoox]

It really depends what the cable is carrying as far as signal. If the power cable is armoured that provides a reasonable level of screening that will reduce radiated EMC, and an armoured screened shielded CAT6 cable will protect from susceptance to EMC. Coms cables using twisted pairs like CAT 5,6 etc also reduce common mode issues.

cool, those could be options then. I find it strange that fibre optic is not immune to EMC

Have you thought about just using ethernet over power adaptors for the internet connection rather than cable?

nope didn't consider that option - is it reliable I wonder, and at what speeds. I will have 150mbit fibre to house so would hope to keep most of that speed in the garden room

 

[Molynoox]

Don't forget that building regs apply to the depth, fall, bedding, jointing and inspection arrangements for the foul drainage - can't remomber which approved doc it is. Where the water pipe goes from internal to external and vice versa I'd do pipe in pipe to ease installation and protect it - you've obviously spotted that it needs to be 750 deep min to protect from frost - I'd put an isolation valve outside the new build in a suitable chamber. Wiring regs apply to the type and installation method for power - I'd consult a spark to make sure that you choose the correct type of SWA cable and installation methods (the workshop may or may not also require its own earth rod, depending on what the spark recommends). I agree with the idea of putting a separate conduit for data cable, with a pulling rope installed before you bury it.
PS building regs may also require you to have an SVP or a durgo valve at the upstream end

some excellent points there thanks!

It is part H for drainage and waste, I am reading it now

plumber is sorting the SVP valve

for isolation valve, could I not just have something inside the building, like a little valve that sits in line with the pipe?

 

[Inspector]

You might want to put the wires needed for burglar alarms in there too.
Pete.

 

[joshvegas]

Your inspection chamber ( assuming that big yellow dot is a 450mm IC (not a manhole) means you don't need a rodding point as your pipe run is straight. If its existing though you might find you need a deeper one if you are including a toilet that waste pipe needs to be 1in40 from memory so you'll have a reasonable drop to get across the garden especially if the ground falls away from your house.

 

[Molynoox]

You might want to put the wires needed for burglar alarms in there too.
Pete.

Good idea!

 

[Molynoox]

Your inspection chamber ( assuming that big yellow dot is a 450mm IC (not a manhole) means you don't need a rodding point as your pipe run is straight. If its existing though you might find you need a deeper one if you are including a toilet that waste pipe needs to be 1in40 from memory so you'll have a reasonable drop to get across the garden especially if the ground falls away from your house.

Ah, inspection chamber, that is the terminology I was missing! Yes I read part H last night and I your comment confirms what I took from those. I have enough drop to use existing IC I think. Plumber thinks so too. And yes it's 1 in 40.

 

[gmgmgm]

Coming in a bit late here. Do you need those two 90 degree changes of direction? Much better to have straight or even gently curved trenches.

And while I'd recommend separating power from communications, realistically over 15m it won't matter. Putting them all (cat5/6, power, alarm wires(just use a couple of spare cat5)) in a single 100mm conduit won't be a problem from a crosstalk POV, but go with screened cat6 for peace of mind.

Consider also the access to conduits- for some buildings I have a manhole outside the building with a straight conduit run to the manhole outside the other building, which makes it fairly easy to check what's going on. But keep it simple

 

[Molynoox]

Cool thanks. I can avoid the 90 degree bend so I will, cheers
For alarm cable.. will cat6 have enough cores? I typed in alarm cable to Google and results ranged from 4, 6 and 8 core.

Martin

 

[flying haggis]

cat5/6 is 8 core so enough for alarms. I would put at least one spare cat5/6 in as well or put in and leave a draw rope. could you put the comms duct on the other side of the waste thereby keeping the max distance away from the power

 

[MarkAW]

Don't forget to account for a fall in your waste. One end of the trench will need to be deeper than the other