Running utilities to an outbuilding

[kingandy2nd]

Morning Guys,

I'm looking to have power and water in my new detached garage, and I'm just trying to get my head around the best way to do it.

In respect of water, I believe the best way is to T-off the blue plastic supply line to the house and bury the pipe more that 750mm deep. However that would require me to dig a 25m trench due to the site location vs the water supply. I have a supply to a tap at the rear of my house. Could I t-off that (with some suitable insulation, and then take that underground in plastic pipe to the garage (which would be a 5m trench)? Or should/could I bring the plastic pipe into the house somehow near that tap and form a connection?

With respect to power, I wanted to run a 10mm cable through the house from the CU to an external wall, then have an IP65 junction box where I'd switch the cable to be a 10mm armoured cable, and I'd look to stick it in the same trench as the water pipe.

Any suggestions/feedback welcome.

Thanks
Andy

 

[motorbiking]

10mm is a b**ch to work with, could you not use a ring? Are you going above 32A?
For the water - I'd be tempted to T off the outside tap and run it down the wall, particularly if the house isn't insulated to current standards and therefore likely to leak enough heat to prevent the cold pipe from freezing on the surface mount. If you are bothered you could box it in which will avoid UV damage to the insulation.

 

[jeds]

Tee off at the closest point. 750mm deep or insulated pipe. Blue pipes are normally insulated with Shallowduct (expensive) but that's up to the stop tap. After the stop tap you can do what you like really. Your cable sounds ok, but the more important thing is circuit protection, which should ultimately be designed by a spark.

 

[kingandy2nd]

Thanks for the quick replies folks.

10mm is a b**ch to work with, could you not use a ring? Are you going above 32A?
For the water - I'd be tempted to T off the outside tap and run it down the wall, particularly if the house isn't insulated to current standards and therefore likely to leak enough heat to prevent the cold pipe from freezing on the surface mount. If you are bothered you could box it in which will avoid UV damage to the insulation.

My welder needs a 32a feed, so I figured I'd go for 10mm cable to allow the welder to be used with the lights on.

Yeah I would look to box the pipe in if I go from the outside tap. I probably should have mentioned that this is a 33m2 outbuilding so it has BC involved...so would they approve or frown on such an approach?

Tee off at the closest point. 750mm deep or insulated pipe. Blue pipes are normally insulated with Shallowduct (expensive) but that's up to the stop tap. After the stop tap you can do what you like really. Your cable sounds ok, but the more important thing is circuit protection, which should ultimately be designed by a spark.

Sorry Jeds, do you mean I should just use the tap for the tee, or should I be going to the mains pipe? I'd not heard of shallow duct before, but for a short run I'd be tempted to use it all the way to save me digging so deep.

I'll take the 10mm cable to the CU. I guess it might go into my existing CU, or connected via henley blocks to the main cables, as I plan to have a CU in the garage anyway.

 

[jeds]

The connection could be from the outside tap, or somewhere below your sink and then take it through the wall. The tricky bit is getting it below ground. If it runs down an outside wall, you'll need to box it into some sort of insulated housing until it gets below ground.

 

[cdbe]

You will need a installation certificate for the electrics so get an electrician to design/size it - oversizing will just waste your money. You shouldn't really break into the water supply pipe before the main internal stoptap. If you're having water then don't forget drainage.

I never bothered with water in my end of garden garage, if I get round to it I'll get a rainwater harvest system with a storage tank just for hand washing and cooling my welds etc.

 

[thomp1983]

I used an insuduct when bringing my new water feed (25mm blue mdpe) up the outside of our new extension from below ground, not badly oriced in the scheme of things and if you use a hockey stick bend to go through the wall it's fairly neat.

 

[Mr Chibs]

Think my outbuilding is supplied with 16mm swa (armoured cable), this comes from house (CU).
I questioned the size, as it's quite a large cable (physically)... remember the sparky saying it was something to do with the size of the earth cable.

 

[oldbutnotdead]

Is this outbuilding already there or still at the planning stage? What are you going to do about drainage if you have a tap in there? If the gutters are going to a soakaway you absolutely cannot connect a sink or whatever to that- if you're only putting an outside tap on I wouldnt waste the effort, just use a long hosepipe.
Power wise do go big- I've only got a 'standard' hobby MIG but that runs so much better now its actually getting 240v (used to have to run it on a long extension). If yours is actually pulling 32A you may be on thin ice with your supplier- that sort of load is meant to be notified on a domestic supply.
And yes Building Control will be interested in water supply and drainage (unless they've signed it off already, in which case for the drainage at least you're looking at another Building Notice. The electrickery- new circuit is always notifiable, BC will charge you a fortune, much better off getting a self-certifying electrician to design the scheme & specify the trench depth, fill method etc. and make the connections (most will be happy for you to bury the cable long as you take pics). Don't forget to chuck a duct in for Ethernet, alarm cables, any other comms you might fancy.

 

[kingandy2nd]

Think my outbuilding is supplied with 16mm swa (armoured cable), this comes from house (CU).
I questioned the size, as it's quite a large cable (physically)... remember the sparky saying it was something to do with the size of the earth cable.

Thanks for this. 16mm isn’t a massive increase in price over 10mm so I’ll go for that.

Is this outbuilding already there or still at the planning stage? What are you going to do about drainage if you have a tap in there? If the gutters are going to a soakaway you absolutely cannot connect a sink or whatever to that- if you're only putting an outside tap on I wouldnt waste the effort, just use a long hosepipe.
Power wise do go big- I've only got a 'standard' hobby MIG but that runs so much better now its actually getting 240v (used to have to run it on a long extension). If yours is actually pulling 32A you may be on thin ice with your supplier- that sort of load is meant to be notified on a domestic supply.
And yes Building Control will be interested in water supply and drainage (unless they've signed it off already, in which case for the drainage at least you're looking at another Building Notice. The electrickery- new circuit is always notifiable, BC will charge you a fortune, much better off getting a self-certifying electrician to design the scheme & specify the trench depth, fill method etc. and make the connections (most will be happy for you to bury the cable long as you take pics). Don't forget to chuck a duct in for Ethernet, alarm cables, any other comms you might fancy.

It’s a new build garage. Drainage isn’t a problem as there’s a nearby manhole for waste water and I’ve already got a soakaway installed which I can enlarge for the rainwater.

My spark is good in so much as he’s happy for me to do cable runs and then he can come in an connect/certify. Good point about an Ethernet cable to go in there too

Thanks folks

 

[oldbutnotdead]

Consider putting a loo in a corner since you have drainage- saves traipsing down to the house covered in oil and getting soaked in the rain when you need a wee .
Also re electrical supply, don't let your spark supply the garage via an RCD in the house- mine is wired via Henley blocks to a standalone MCB for cable protection, RCD is in the garage CU. Means you don't knock the house out with a garage fault, also you don't have to drag back to the house to reset a garage fault.