3" Soil pipe

9 Jun 2014
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United Kingdom

I have a blockage in my cast iron 3" soil pipe. The toilet is blocked up and the bath is also not draining away as the 40mm plastic pipe fits into the cast iron tee section.

I think the easiest thing to do is cut out the cast iron suff and replace in plastic. However i cannot find any 3" pipe, it is all in 110mm.

So do i just cut the cast off at ground level ? This is pretty straight forward, but how do i connect up 110mm plastic to the smaller cast pipe ?

OR is there 3" stuff i can buy so i keep the cast above the Tee (where the waste enters the pipe) and have plastic in the lower section? I hope this is ok to understand.

Any help appreciated.
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This is the stack. Would you keep the cast up to the first collar and then renew.

Is it best doing it all in 4" ? IMG_1442.jpg
Ok, so there is no fitting which will fit into the cast ? I have used these adapters on underground before, didn't know you used then on soil pipe on the wall.
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it is above ground (i think). Is there any way to say where the blockage is. I assume not and so just need to break into the soil stack - starting around the Tee area.

What do you use to clear a blockage like this anyway ? There is no rodding point is there.
Before you get to the point of replacing, I'd be inclined to see if the blockage could be shifted by mechanical means or jetting. How much cast is there above that branch?
As Prentice mentions, there's a lot of weight in all that.
Ok, but where do you jet or use a rod from ? Would you take the toilet off and rod from inside the house down the outlet pipe ?

Also when you mention about the weight why is it a problem ? Don't you remove from the top down, so doing a section at a time. Fairly standard stuff really plus i can just drop to the floor and only tarmac to be marked.
Drop that from any height and its likely to shatter into a lot of pieces, and make one hell of a mess. Personally, I'd be cutting into the plastic section you've already got, and attempting to clear from there initially, plastic can soon be repaired with a slip collar.

Failing that, or if you really want to replace the lot, either start in 110mm from the drain under the tarmac area, or run in 82mm from a suitable point. Do not reduce from 110mm to 3" or you'll be setting yourself up for a lifetime of misery, constantly unblocking it! :eek:
As above, remove the plastic section and try rodding from there, do this externally rather than internal, reducing any mess in the property. Even removing a section of cast at a time is going to be weighty, so not something that you want to be doing on your lonesome, and if dropping, it will destroy the tarmac and damage anything else that it may come in contact with. Looks like your on a road side and public path, so i would be taking all the precautions required to stop damage/injury.
Is there an inspection chamber nearby? Can you lift it and see if it's full? Can that be cleared and then rodded backwards to your stack? Try all that first to see if you can clear the stack then, if this is a reoccurring problem that causes enough of a nuisance to you then consider replacing it all in 4" plastic! You may want to think about going into the ground with the 4" to so as to remove any bottle necks.

The fernco / flexi adaptors are fine to you for this purpose (only way really) and when reframing the stack, make sure to design in cleaning eyes and an access plate at the lowest level.

If you can't clear the blockage and the stack is full of s**t you will make one hell of a mess :eek:

Cut at low level with a grinder, taking care the stack above won't drop, then another cut just above, to remove a section of pipe, insert a thin board, sheet, rubble sack on top of the open drain and smash the rest above with a club hammer, working upwards, it will shatter in bits so watch your eyes!

Good luck (y)
Why do you say it is a soil pipe?

Looks to me like a rainwater pipe that someone has attached a waste-pipe to.
The house is 100yrs old and this looks to be what was there originally. The soil pipe was changed into the tee 10yrs ago because the previous owners baby put a toy down there and so it blocked things up.

Another question if i may: Can i change the tee area and lower pipe work into 3" plastic ? This way i can put in rodding eyes etc. Do they make pipe in this cast size in plastic ? Is the stuff i need basic rainwater downpipes ?
Rainwater downpipe is 68mm and not compatible with soil pipe and fittings. Soil pipe and fittings are available in 82mm diameter, anything smaller is never going to work on a WC pan for obvious reasons. ;) 82mm is unlikely to be available as widely as 110mm, you may have to go to a larger merchants to find what you need. (Its more expensive than 110mm too IIRC.)

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