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Replacing cast iron soil pipe with plastic - Piglet John!

(7 Posts)

We have a leaky toilet and the plumber has diagnosed the cast iron soil pipe which is attached behind the toilet to the plastic waste needs completely replacing as iron to plastic doesn't work. We had the bathroom redone 2 years ago by a 'plumber' who we discovered afterwards wasn't after all.
The soil pipe behind the boxing in the bathroom and the hall needs to be cut out and the bathroom floor got up to connect the waste to the bath and basin.
We have been quoted £12000 for 2.5 days work x 2 men, does this seem a lot. The plumber knows we are desperate and need it doing asap!
Piglet John!!! Please help!!

PigletJohn Tue 17-May-16 19:12:40

is there an iron soil pipe attached to the outside wall of your house? And a roughly horizontal branch from your WC to this pipe? How long is the branch?

Some photos would help.

Did you mean to type twelve thousand pounds? Or did you mean twelve hundred?


Thanks for replying Piglet John. Oops, no meant £1,200. The iron pipe is boxed in inside the house, it runs right next to the toilet so can't actually see it. The horizontal branch to the toilet is approx 1 foot. Sorry, not able to get photos as its in a rental hence can't leave tenants without a bathroom for long.

PigletJohn Tue 17-May-16 19:46:46

It's unusual to have an iron soilpipe inside the house. Round here old houses have an iron pipe on the outside, and young houses have a plastic pipe on the inside.

I expect they will cut off the iron socket and fit some kind of plastic adaptor. It needs care to prevent iron fragments falling down into the pipe and causing a blockage. They might use a diamond wheel. Outdoors it can be done by using a blowtorch to melt the lead solder that holds the joints together, or you might remove the iron stack and renew it in plastic (less worrying).

I'm picturing something from page 54 of the McAlpine catalogue. I don't agree that plastic and iron can't be connected, but it is an awkward job that might go wrong and take longer.

You need an experienced old plumber who is happy working with iron. Possibly they have quoted a high price because they aren't looking forward to the job. Are they young? You could ask around and see if there is a recommended wrinkly local person who would like it. Unless you are in central London, £300 per person per day should be plenty.


It's a 1950's ex council house. The plumber indicated the soil pipe be cut off at the ground floor level (before it goes outside underground) and be reconnected to the plastic. Great to see attachments are available to connect iron to plastic. It's tricky because at ground level the mains pipe runs infront in the boxed in section in the hall below as the cockstop tap is there. I wondered if it's possible to cut iron off in bathroom and reconnect plastic there to save the replastering, re tiling etc. Do you think this is possible, obviously can't see inside the walls so difficult to see where connection could be possible.
Our regular plumber is booked up for a while and said not many plumbers would want to do a heavy smelly job.

PigletJohn Tue 17-May-16 20:07:50

If it's an obstruction, I would be inclined to cut the incoming water pipe and get it out of the way, reinstate it afterwards, much easier than grappling with a big, sharp, very heavy, iron pipe.

Replacing the whole soil stack in plastic will make it easier, and to reconnect, also for any future work that's needed.

Also consider having the duct boxed-in using screws and preferably not tiled, so future plumbing will be easier. Mine is done in short WBP ply sections for this reason.


Many thanks, I feel very educated on soil pipes today!

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