Joining non standard PVC stormwater pipe?

[rscho]

While investigating a blocked PVC stormwater pipe we found it was concreted into an old cast-iron pipe which ran about 15 metres before discharging to the gutter. The cast-iron pipe had failed long ago so we decided to replace it with PVC and tee into a 100mm PVC stormwater pipe we ran two years ago.

However when we went to connect the two we found that they are very slightly different in diameter, so that the old PVC pipe fits neatly into the non-socket end of the
newer 100mm PVC pipe. The older pipe also has a thinner wall and its outside diameter is 4", while the newer PVC pipe has an inside diameter of about 4". I don't think pipe cement can reliably bond the two as its not really a snug taper fit, so I'm considering using a bitumen type sealer (hydroseal?) along the mating faces.

My questions are: Why the slight difference in size? Could one be stormwater and the other sewer pipe? I thought all sizes had been standardised and I can't find any pipe that matches the older PVC.
Does anyone have any other suggestions to make a water-tight (tree-root tight) seal?

Thanks in advance.

[doug1]

Hi

If I am reading your post correctly you are joining pvc to pvc.

I regularly join or create fittings from marley now icon I believe white pcc guttering cement

it cures to a white pvc much the same as marley stormcloud guttering colour and is workable when cured as pvc

hope this helps
Doug

[bsrlee]

1: you have to use a special prep solution when joining to 'old' PVC pipe - IIRC they put red dye in it instead of blue for regular glue.

2: there now seems to be 90mm drain pipe and 100mm 'pressure' pipe, at least thats what I've seen at Bunnies & Reece. That's 3.5" and 4" near enough in the old money - so you can probably slide one inside the other, and the 90mm drain/stormwater pipe is thinner as it does not have to resist mains pressure.

[Tools]

1: you have to use a special prep solution when joining to 'old' PVC pipe - IIRC they put red dye in it instead of blue for regular glue.

That's called primimg fluid, but it does not replace the glue. It just takes the shine off the pipe and cleans it ready for the blue glue.Priming fluid is used on new pipes as well, not just old.

Tools

[montiee]

That's called primimg fluid, but it does not replace the glue. It just takes the shine off the pipe and cleans it ready for the blue glue.Priming fluid is used on new pipes as well, not just old.

Tools

Yeh I was about to say. You need to use both primer (red) and the glue (blue) regardless of age if you want to do it properly. The red primer once on stains the pipe permanently (wish I knew that before ). No chance of wiping it off so be careful not to splash it all over the place if you want a neat job.

As for PVC pipes differences I found that they've changed over the years. Not sure when. My dad handed me an old S/P bend set and the diameters were slightly too large for todays fittings. Luckily I realised that for the price of the washers that I needed to buy I could get a whole S/P set cheaper and of the right size so I didn't play games of find the leak later on and just bought a new one. Personally I'd rip out the old pipe and lay it again with the latest pvc and fittings and avoid the hassle later on unless it's too difficult.

[wonderplumb]

PVC pipe hasnt changed a bit since it was bought out, regardless of type, size, manufacturer etc.
The only difference they had was pvc for underground and pvc that was uv resistant for outside stuff.
It sounds like you are trying to connect 90mm to 100mm for which you will need a 100 x 90 'donut' or reducing bush and it fits inside the 100mm pipe.