Joining Cast Iron to Plastic

3 Feb 2008
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United Kingdom
Am putting in a new bathroom for my elderly parents, and have stripped the old bathroom back to nothing, and am planning to replace all the waste and copper, as some of it is imperial rather than metric, so I thought it better to start from scratch.

The one job I need to start on is the soil stack. This is black in colour, and think it's cast iron, and I'd like to replace it with plastic, so I can change the position of the WC and sink without any aggro.

What's the best way of connecting cast iron to metric plastic?

I've seen that Screwfix sell a flexible adaptors - are they suitable?

Alternatively, if I cut the cast iron, could I just use a standard plastic coupling to join plastic to cast iron?

Any help greatly appreciated.
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Your better off with a time-saver coupling however it depends on what sort of CI you have.

There are a lot of different sizes and thicknesses.

For example there is 3&1/2" number one on soil stacks or 4" number one (approx 3/8 inch thick).

Best thing to do is source where to buy the time saver coupling and take a cutting of the cast with you when you go to buy it.
Thanks for this information - most helpful

Do you think PlumbCenter stock these timesaver couplings, or are they normally something they have to get in specially?

The next thing is - what's the best thing to get a sample of this pipe out, so I can take it to the shop?

Do you think an angle grinder will go through it OK, or is there an easier way?

Presumably it's pretty heavy, so it may prove difficult!
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