epsilonGreedy

Achieving a clean square cut with plastic 110mm pipe, how.

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Just looking for some practical tips on cutting underground drainage pipe, eg saw type and particularly how to obtain a 90 degree cut.

 

I understand that when joining push-fit foul drain pipe sections it is good practice to push a coupling fully home then ease it back 10 to 15mm so that any ground movement does not stress the joint. From this I infer that pipe cuts do not need to be millimeter perfect but a cut 5mm out of true from a square cut would be a long term liability to seal integrity.

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Mitre box and a good sharp hand saw. Don’t forget to chamfer the edges on it or you will tear the seal. I wouldn’t be pulling any joints back as they won’t move that much - shouldn’t need it if everything is properly bedded. 

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I've wrapped a bit of square edged paper around pipe before now to mark a dead-square line around the pipe.  As long as the paper is wrapped tightly around the pipe and the edges are aligned at the overlap then the line marked by tracing along the edge with a marker will be perpendicular to the pipe axis. 

 

For putting a taper on the end of 110mm pipe I used a belt sander, with the pipe resting in a corner and being twisted around with one hand whilst the belt sander was held at an angle with the other hand.  To finish the taper off I just used a Stanley knife as a scraper, held perpendicular to the bevel and scraped around to smooth off the bevel and get rid of the fluffy bits of plastic that remain.

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Use a chop saw and finish the last bit with a slightly blunt hand saw.

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24 minutes ago, PeterW said:

Mitre box and a good sharp hand saw. Don’t forget to chamfer the edges on it or you will tear the seal. I wouldn’t be pulling any joints back as they won’t move that much - shouldn’t need it if everything is properly bedded.

 

 

I got the advice about pulling back the joint a touch from a YouTube instructional video produced by one of the large UK manufacturer of underground drainage. Also the old-time semi retired builder who helped me during the early stages of the build demonstrated the same technique as he was laying the main foul drain onto my site.

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I would be worried about pipes moving that much that a joint or an inspection chamber moved 10mm..!! I wouldn’t want a 10mm gap as crap/crud etc will build up on that edge and slow things up. 

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if you have a bunch of cuts to do - fix a couple of bits of wood (parallel to pipe)to a surface that hold the 110mm pipe nicely on the surface (stop it rolling on surface).

Much easier then to do cuts/chamfering.

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The 10mm gap is really good on soil stacks as the expansion / contraction of the pipe can cause noises.  Probably not an issue with below ground stuff though.

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a finer toothed saw as you would use for plastic roof sheeting is best solution

https://www.cabp.co.uk/Accessories/Tools/Spear--Jackson-PVC-Predator-Saw-14-PPI_TPVPRE.htm

  to get a nice cut if no table saw available--table saw works cos of speed of blade

std hard point wood saw is a bit coarse by choice

ideally the way you decide on TPI of a saw is you want at lest 2 to 3 teeth in the thickness of the material you are cutting then it will cut smooth and  not snag

16tpi will be even better for plumbing plastics

Edited by scottishjohn
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1 minute ago, PeterW said:

I would be worried about pipes moving that much that a joint or an inspection chamber moved 10mm..!! I wouldn’t want a 10mm gap as crap/crud etc will build up on that edge and slow things up. 

 

 

Yes I had the same concern. When pushed fully home the plastic joints are pretty seamless.

 

The video I watched did involve drainage bridging over footing blockwork and it emphasized that plastic drainage should not be subject to any stresses at joints when the ground moves hence the pullback technique. I guess it is a trade off between best seamless joints and zero worry about plastic crunching stresses at joints should there be some ground movement.

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Through footings is different ..! There are standard details for this sort of stuff and you can get specialist movement joints. I’d much prefer a seamless joint and a tiny risk of movement over the other option any day..!

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I think this is why lots of people especially in  USA use glue fittings and not push on if going under ground --suspect they have to to comply with code

watched a UK video and they said push them right home --then pull out appox 10mm to allow for expansion and contraction

Edited by scottishjohn

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41 minutes ago, JSHarris said:

I've wrapped a bit of square edged paper around pipe before now to mark a dead-square line around the pipe.  As long as the paper is wrapped tightly around the pipe and the edges are aligned at the overlap then the line marked by tracing along the edge with a marker will be perpendicular to the pipe axis. 

 

 

I like it, suitably low-tech for me.

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Just now, scottishjohn said:

I think this is why lots of people especially in  USA use glue fittings and not push on if going under ground --suspect they have to to comply with code

 

A lot of the schedule pipe in the US is ABS  and not PE / HDPE / uPVC so forming sockets etc on pipes is a lot more difficult. Glued pipes are more susceptible to ground damage as the joints tend to shear. - you get some flexibility  with the UK and EU methods and it’s a lot easier to demount and remake joints than with ABS. 

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2 hours ago, scottishjohn said:

https://www.youtube.com/channel/UClqplhfuIHgG1bcpkWcpRuQ

lots of how to do it videos here

 

 

A useful collection of advice videos there, thanks. Having watched the pipe cutting episode I am reassured I will do better using the @JSHarristechnique. Even on the low resolution instruction video I could see the resulting cut was something like a 5mm out of true. If that is what pro's do when on best public video behviour I need not worry about my diy standard  🙂

 

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correct --plenty of length  even after you pull them back a little

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A felt tip marker and a 4 inch grinder.  You can the chamfer the edges with the same grinder.  A quick rub with some sand paper will get rid of any stringy bits after you chamfer it. 

Don't for get to grease the leading edge  and the collar with joint lubricant.  Not  fairy liquid or Spit or any other old wives tale stuff. 

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Buy a soil pipe wall bracket and clamp it on. Use that as a guide for your handsaw.

 

Or keep an offcut of pipe with a split and use that to draw around or as a guide for your multi tool.

 

Like I did on this pipe to cover the water meter:

 

20161030_121226

 

Or use a mitre block (& Bacho saw):

 

20170225_110344

 

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5 minutes ago, Declan52 said:

 

Don't for get to grease the leading edge  and the collar with joint lubricant.  Not  fairy liquid or Spit or any other old wives tale stuff. 

 

The pot of pipe lube kept being given the youngest lad on our ground works team towards the end of each day - along with suitable comments as to the use he might have for it that evening.  Trouble was the lad was a bit shy and used to go bright crimson every time the other lads did it, which made them take the mickey out of him even more...

 

You can DIY the pipe lube easily enough if you want loads of it and don't want to pay for the ready made stuff.  It's usually just water mixed with about 20% glycerine and thickened to a gel with methyl cellulose.

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Here you go, forget the hand saw unless you just like hard work, or your like Fred dibnah and like doing stuff like in the olden days

cordless grinder and buy a pipe chamfering tool. 

Get a can of silicon spray for the rubber seals, and a clean towel for your hands or you will be slipping around like a greasy pig. 

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