Water / Electric / Gas supply to Garage.

13 Sep 2009
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United Kingdom
I'm flagging the patio at the back of house and need to think about water, electric and gas feeds to the garage (not built yet) 20m away at end of garden. I'm digging a trench to lay pipes before i flag over, and laying 25mm blue mdpe (water), 6mm 3core armoured (electric) + mdpe yellow (gas) or tracpipe.

1. Is it ok to lay all 3 pipes in same trench?
2. What size gas pipe would i need for either a wall heater or for a small combi boiler supplying 1 radiator (not sure which heating source to go with as yet)?
3.Would i be better to lay 100mm flexible plastic conduit instead and feed all 3 pipes through at a later date, so as to avoid having pipes coiled up on garden (probably be another year or so before garage is built)?

All pipes will be going under garden and patio, through kitchen wall and under suspended wooden floor.
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Gas has to be at least 25mm from electric cables.

I dont think you need an armoured cable if its in a duct.

1 - yes, provided they are at the correct depth and at least the mimimum required distance from each other.
2 - No way to tell from the info given.
3 - No.

Cable will need to be armoured regardless of plastic ducting or not. 3 core is almost certainly the wrong choice, and 6mm might not be suitable either.

Combi boiler and 1 radiator sounds like a total waste of money, and good luck finding one which has an output low enough to supply only one radiator.

Where is the waste water going?
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Whats needed depends totally on what you plan to do in there!

Its normal to use two core and use the metal sheath as the earth.

FP, where does a requirement for an SWA cable arise if in a duct?

I plan to use the garage primarily as a studio for painting and guitar playing amps etc. Maybe as a general workshop too. Would be nice to have a good source of heating hence i thought gas. I just thought if i'm digging a trench for electric and water, may as well put gas in too. Maybe it's more hassle than it's worth and i should just go for an electric heater. Just gonna have sink/cold tap with waste running into gravel strip.

My electrician advised to go with 6mm 3core armoured just to be sure although yes maybe ott.
And you cannot run MDPE into your Building it is for bellow ground use, or external if in a proper protective Sleeve ;)
Most flats take the MDPE into a GF room. Some up to upper flats.

Do you know of any reg relating to that?
Most flats take the MDPE into a GF room. Some up to upper flats.
Built in 1986, our 3 storey blocks have blue MDPE for all 3 storeys adapted to copper behind a 4' high stud wall in the GF bathroom. All 3 are accessible from outside via 2 cast iron access plates in the wall. There are 3 stoptaps, 1 for each flat behind the plates.

Yellow MDPE terminates outside the building, going to each floor in steel, externally fitted.

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