Goodness how many variations of 300mm twinwall drainage pipe are there?

[Alan Ambrose]

... I'm trying to join (as measured) 303 mm id / 352 mm od to ... 275mm id / 380mm od.

 

The first one, is an Accesso inspection chamber, the 2nd unknown as yet.

 

Just one of life's little challenges, grrr.

 

[Alan Ambrose]

Anyone? I'm thinking, even though it was apparently installed less than 10 years ago, that the ~275mm id / 380mm od must be some old imperial size or old design.

 

As far as I can see, the 300mm twinwall versions by Naylor, Polypipe, JFC, Wavin and Cherry (and probably Brett Martin) are all fairly compatible ... and not the same size as the pipe that is installed.

[Marvin]

Hi @Alan Ambrose

 

Could it be this stuff?

 

https://unitedcivilssupplies.co.uk/shop/twinwall-drainage/300mm-solid-unperforated-twinwall-surface-water-pipe-x-6m/

 

Perhaps they have fittings to help.

 

M

[Alan Ambrose]

Thanks, but that's the Naylor stuff -  I think this must be older or more obscure. There are some wacky rubber seal fittings to clamping sum close sizes together tho.

[Dave Jones]

300mm is massive, does it serve a housing estate ?

[Alan Ambrose]

Not really  It's an existing ditch that runs behind 3 properties in the countryside which we want to link up to. This was turned into a piped culvert about 10 years ago.

 

I think this kind of 300mm twinwall pipe is the first thing that farmers/countryfolk think of when they consider culverts & ditches & rainwater.

 

BTW in my twinwall travels I discovered this chart (below). The pipe is reputed to have an 1:80 gradient suggesting 1.8m/s & 150l/s. So, yeah, theoretically enough for 75 SuDS compliant houses if it was laid correctly and if the other houses used attenuation (they don't and one neighbour says it wasn't).

 

[Alan Ambrose]

Ah, I've figured it out . I did this kind of thing (straight bits of wood held on with bungees, measure above and below the pipe and average the numbers). Then same from side-to-side.

 

So, 373mm od side-to-side  and 336mm od vertically - so, tada, the pipe is a bit squashed and averaged again the overall diameter is ~354mm i.e. standard size OD for 300mm twinwall. It was the obviously bigger diameter seen from above that was putting me off.

 

Now all I have to do is fit the damn thing. BTW there are at least two suppliers of flexible rubber couplings & adaptors ... flexseal and VIPseal. You can pretty much attach any diameter to any somewhat-in-the-same-ballpark diameter. e.g.:

 

https://www.vipseal.co.uk/product/vsc-standard-couplings-2

 

https://www.fernco.co.uk/assets/Data-Sheets-Folder/Flexseal-Standard-Couplings.pdf