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digging a trench

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  1. #1
    Senior Member ForeverYoung's Avatar
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    Default digging a trench

    Sorry, being a bit lazy with the searching, and I should know...

    Need to dig a trench to lay some new water pipe for garden taps, how deep should it be?
    I was going to ask the plumber today when he came to assess the project, but he didn't turn up and I am going to start digging in the morning.

    My experience with yard plumbing was back in the days when it was copper but part of what just got ripped up (about 3 inches below the surface in most places) was 3/4" PVC pipe (potable), is that the go these days? And am I allowed to lay it myself? I will get the plumber to tap it into the pipe running to the house (presumably copper, might even be gal).

    I have done some siteworks for a new shed, rock retaining yet to be backfilled, so thought I could lay the pipe in there for part of the run, then when the free fill arrives just bury it.
    That will save trenching about 10 metres, just another 5 or 6 on one side to get to the main feed, and 3 or so the other for the tap.

    And while I am here and lazy what is the depth for electrical conduit? Think it was 400mm from memory? With tape and maybe timber on top so a shovel doesn't go through it ... what are the regs if it is the same trench as the water pipe?

    thanks.

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    ...you lazy so and so!!

    Not sure of WA regs. Here in Vic, its 500mm....so generally the trench is dug at 600mm to allow for the conduit height. The tape is placed at 300mm above the conduit.

    Water pipe....mmm not sure from memory what clearances are required or if there is a minium depth...suggest that anything below the grass roots would be fine (tongue in cheek comment) but if it were me, 300 to 400mm and allow enough clearance to work on it if required

    In terms of pipe material, I've only used Blueline pole pipe which is rated at higher pressures. Depending on distance, suggest 20 to 25mm will be fine on a town block scenerio. There are fittings to transition from blue line poly to copper...all very easy to use....not sure on poly to gal.

    Also dont forget to take pics and record depth and offsets to allow for future location of assets. If you hand draw it, take a photo and store it in a folder (cloud service such as one drive or google drive) so you never loose it of spend days looking for the scrap of paper!!!

  3. #3
    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by Bart1080 View Post
    ..Here in Vic, its 500mm....so generally the trench is dug at 600mm to allow for the conduit height. The tape is placed at 300mm above the conduit...
    thanks
    I vaguely remember a post where it was discussed about the regs for water and elec in the same trench.
    Doesn't seem like a great idea tbh but I guess there isn't too much difference to having parallel trenches and a spacing, say 200mm, between them in the same trench.

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    My post I think on a combined services trench.
    We have water, power and comms in the same trench so the trench depth was the power minimum
    "A big boy did it and ran away"

    Legal disclaimer denying responsibility to be inserted here.

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    The main services line into our property (100M run or so) has power, water and data all in the one trench. When I had a brainwave to dig down to intercept the water line it was about 800mm down, with tape under the water saying electricity below. That was not a fun job.
    When I put blueline polly in for our irrigation I try and get about 300 to 400mm down, which is about the depth the ripper go's on my mini skid steer.

    Dave.

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    last time i did this was in my back yard and was full of damn rock, took an entire day to trench 600mm 25 metres long with a dingo and trench attachment.

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    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by wozzzzza View Post
    last time i did this was in my back yard and was full of damn rock, took an entire day to trench 600mm 25 metres long with a dingo and trench attachment.
    Last time I did it was about 12 metres from memory. Rock all the way, and compressed under the driveway. Did it by hand. Think it took me about a week, a few hours each day. Last few metres was under a big tree so I washed out the roots with a hose - I wanted to save the tree. I can be a bit of an idiot sometimes.

    Last one:
    trench-1.jpg wp_20160816_12_55_37_pro.jpg

    This one, yep, lots of rock.
    And it's only 40Ý+ today, but I am crook so day off.

  8. #8
    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by Moondog55 View Post
    My post I think on a combined services trench.
    We have water, power and comms in the same trench so the trench depth was the power minimum
    ah, thanks, that made it easier to search.
    Lots of good intel in the replies.
    Your threads:
    Combined services trenching (renovateforum.com)
    combined services trench?? (renovateforum.com)

    So in round figures I can dig 600mm deep for the elec.
    Put some tape (and a run of timber, cause I do) 200mm above that.
    Then the water (which only has to be 100mm separation from the elec - which means the water would be 300mm underground.
    Now, where is that pick axe?

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    Quote Originally Posted by ForeverYoung View Post
    (and a run of timber, cause I do) 200mm above that.
    do you like to encourage termites into your home?

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    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by wozzzzza View Post
    do you like to encourage termites into your home?
    good point.
    But this is out in the yard, elec run will go from carport to shed.
    My bush block has termites everywhere if I care to look.
    I use drugs to keep them out of the house.

  11. #11
    1K Club Member Pulse's Avatar
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    Default digging a trench

    Donít use wood it just confuses people, use the polymeric cover designed for that purpose if you want additional protection, bit over the top though.

    https://www.jaybro.com.au/cable-cover-5912.html

  12. #12
    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by Pulse View Post
    Don’t use wood it just confuses people, use the polymeric cover designed for that purpose if you want additional protection, bit over the top though.

    https://www.jaybro.com.au/cable-cover-5912.html
    that's a good idea.

  13. #13
    Jon
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    Default digging a trench

    What about a row of bricks as mechanical protection and a warning to slow down for anyone digging in the future. I know if I am digging in an unknown area and I hit a brick or similar I know someone has been there before me and take care.

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    Last time I looked power was 500mm down with a market tape half way up. Water can go in the same trench.

    If you are trenching for water pipe under grass I would go down twice the depth of a lawn corer, I recently upgraded my sprinkler system and I buried it down 300mm, do yourself a favour and hire a machine.

  15. #15
    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by Jon View Post
    What about a row of bricks as mechanical protection and a warning to slow down for anyone digging in the future. I know if I am digging in an unknown area and I hit a brick or similar I know someone has been there before me and take care.
    Yep. I was a bit flippant about the wood.
    Once, decades ago I dug a trench from the house to a shed and used tape and wood (TP offcuts from framing) because I thought it might be in an area that someone in the future would dig over for garden plantings. Another time I threw in some big rocks below the tape.

    Quote Originally Posted by Bros View Post
    Last time I looked power was 500mm down with a market tape half way up. Water can go in the same trench.

    If you are trenching for water pipe under grass I would go down twice the depth of a lawn corer, I recently upgraded my sprinkler system and I buried it down 300mm, do yourself a favour and hire a machine.
    No lawn, or grass here. Darwinian yard - survival of the fittest.
    I will try and get the water trench down 300mm and put the elec in a separate trench.

    I'm not sure hiring a machine is worth it.
    Going from the back of the new shed site towards the side boundary where (I think) the main water line runs from the street to the house is about 6 metres - a lot of rock and tree roots.
    Machine access would be difficult and I am not sure a normal trenching machine would get in there now.

    The siteworks guy I had in to do a scrap and find the levels and possible max size of the shed had a 1.8tonne hoe - maybe I should have got him to scrap out a trench towards the boundary but might have lost a few trees in the process. (one of the rocks he dug up he estimate at 3 tonnes). I might be getting him back with the rock breaker if I really want a 7m wide shed or to get the shed slightly lower. He just did a cut and fill to see what I had - the really big rocks had to stay and might be the level I have to work with.

  16. #16
    Senior Member ForeverYoung's Avatar
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    Tried to upload some pics before but no go.
    Beforeish:
    1-img_20220120_112202.jpg
    Now:
    2-img_20220125_074603.jpg
    Tools:
    3-img_20220125_074622.jpg

  17. #17
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    Quote Originally Posted by ForeverYoung View Post
    I might be getting him back with the rock breaker if I really want a 7m wide shed or to get the shed slightly lower. He just did a cut and fill to see what I had - the really big rocks had to stay and might be the level I have to work with.
    Might cost you a bit as a lot of operators don't like using a hammer as it shakes the machine and accelerates wear on the machine and operator

  18. #18
    Senior Member ForeverYoung's Avatar
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    Quote Originally Posted by Bros View Post
    Might cost you a bit as a lot of operators don't like using a hammer as it shakes the machine and accelerates wear on the machine and operator
    He said he thought about bringing the rock breaker but didn't think he needed it.
    (it seemed pretty obvious to me that there was going to be rock there, and big ones).

    I haven't used this guy before but he was very skilled - could handle that bucket like it was between his thumb and index finger.
    He took down two 15m black wattles with it; lay them on the ground then trimmed all the branches off with the scoop; then balanced the trunk on the bucket to chainsaw to length. Saved me a lot in tree loppers who still would have left the roots in the ground.
    But still, a cowboy of course. Worked really fast, too fast, and did some (minor) things when I wasn't watching which I wouldn't have let him do.
    No biggies in the end.

    He dug this rock out - he reckons 3 tonnes.
    Then rolled it like a marble, downhill, to use as a cornerstone on the retaining.

    7-img_20220130_112811.jpg

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