drill hole into cast iron pipe?

[Jennie]

Hi all,
I need to re-route two pressure relief pipes (one from a combi, one from an unvented cylinder). (I have my unvented qualification).
I'm going to run them both into a tundish, so there'll just be a 22mm pipe to re-route.
Pic below. An extension was done, and pipes are being dealt with retrospectively.
There is the bottom part of a cast iron pipe (rainwater?). It has an overflow pipe from the water softener feeding into it.
Could I run my 22mm prv pipe into it? I'd need to drill a hole. I have a diamond saw bit (also in a pic).
Otherwise, I'm looking at a longish pipe run to get it to the outside wall. I should be able to do it in under 9m (including the bends). But the customer would rather not have a termination pipe on their outside wall.
What do you reckon?
Thanks for your advice,
Jennie

 

[Stigster]

You'll get through with that just fine. Slow and steady and keep the bit cool. I just keep a small container of water next to the job so I can keep dunking it. Even a good Bi-Metal hole saw will go through cast with a bit of patience so that diamond bit you've got will drill through that. The cast iron pipe will be fine if there is something like a basin to flush the pipe out during use. Worcester Bosch put out a technical bulletin about cast iron and condensate from boilers. The D2 from the unvented is fine to take into the cast iron.
TB 0083 a - Condensate discharging into cast iron pipework | Worcester, Bosch Group

 

[steadyon]

If it is a rainwater pipe and the local drainage system is separate foul / surface water, then:

1. The water softener overflow shouldn't be going into it as it will overflow salt water.
2. The boiler condensate shouldn't go into it as its mildly acidic.
3. The unvented cylinder can as its clean water (well at least as clean as surface water).