Numb-nuts 1 Posted June 8, 2015 We have a job pending which will require us to install an underground conduit. I have decided to use MDPE water pipe as its easy to work with and if it keeps water in, it is going to keep water out. The runs we are making are about min 5m and a bigger run of about 25M. We have already experimented with the vacuum cleaner technique of pulling a pull string through and it works okay (Great Fun) sufficient to give us confidence that it will work on the day also. We will be using direct burial rated cat5 cable through the conduit. My question is to those that have the experience in laying underground conduit, at what depth should the water pipe be laid into the ground? MDPE= Medium-Density Polyethylene Please note when pulling cables through remember to pull a new pull string through so that you (or the next person) can pull more cables through in future. Share this post Link to post Share on other sites
jeromephone 6 Posted June 8, 2015 You should pull in a string however if it is a small conduit getting through a 2nd time can be a problem as the string tends to wrap around the existing cables. If you are using the small conduit it may be cheap enough to just do another run with a string in it and nothing else. In this area where we are subject to frost they usually are around 4 feet. You are correct about using the direct bury rated as over time you will get water in the conduit. Share this post Link to post Share on other sites
Numb-nuts 1 Posted June 8, 2015 Yes I thought about the diameter and explained the issues for future use to the client. I estimated for 25mm pipe as the internal diameter is 20.1mm just enough to pull three 6 mm cables through. Fortunately the 25mm pipe will fit into PVC conduit fittings and screw direct into my IP rated Junction box. I only require a single CAT5 external rated This diameter will give an option to add upto 2 more in future without the added expense. I will be introducing a Y coupler with a stop end in one branch so that a vacuum can be operated to draw out moisture and dry out the pipe annually during maintenance. Where the pipe exits the ground there will be a ply housing to hide it as I believe is a common practice. I will also be using 24VAC for current (using 3 pairs) through the pipe as DC getting damp could lead to electrolysis and destroy the cable. I plan to either use a 24VAC camera or transform down at the camera so there is a good 12VDC supply as the run is quite a long one even though the underground portion is only 25M. 4 Feet deep seems rather deep but I'll wait to see what others think. When the pipe carries water it is recommended that it is placed about 2 feet deep, but of course it won't be full of water. 4 feet deep means moving an extra 10-15 cubic meters of dirt Share this post Link to post Share on other sites
the toss 0 Posted June 9, 2015 That will drive some plumber nuts in years to come There is probably some regulation/bylaw that will be contravened by doing this as most conduit & plastic pipe is colour coded for it use. yellow pipe = gas. White conduit = comms, purple pipe = grey water etc. Generally speaking (in Aust) burial is 100mm under hard paved surface, 300mm under non hard paved non trafficable area & 600mm under non hard paved trafficable area Share this post Link to post Share on other sites
Numb-nuts 1 Posted June 9, 2015 I take your point about colour coding but I can't get anything suitable at an affordable cost other than the water pipe which does come in black and that's probably what I'll use. Purple I've seen at the side of motorways for comms cabling. The thing is that both ends of the pipe will be exposed and If I can find a warning tape thats appropriate I will certainly cover the added expense to lay warning tape in the ground just above, At least the pipe won't be carrying any critical services like water or gas. Any power will only be low voltage and will be fuse protected. Share this post Link to post Share on other sites
jazzar 0 Posted June 9, 2015 found this- section 4 may be helpful - didn't read it - covers comms cables. long time since done this but think the marker tape should be about 300m-400mm above the cable so that digging through tape will still give a chance of not hitting cable at a spade depth or bucket scoop using digger. Share this post Link to post Share on other sites
jazzar 0 Posted June 9, 2015 forgot the link from last post - doh. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/33549/spec34.pdf Share this post Link to post Share on other sites
Numb-nuts 1 Posted June 9, 2015 I think I'll take your word for that...! Share this post Link to post Share on other sites
