New soil stack or use existing cast iron one? And which trade?

ChasingtheWelshdream

Mornin’ all on this lovely wet and windy wild Welsh day (bleughh). I am pondering things again.

I am planning an en-suite by pinching some space from an adjacent bedroom. A rough plan means the toilet would be about 5m from an existing cast iron soil stack. The building inspector is happy for us to connect into this but although it is the simplest way, it would look ugly. 

An alternative would be to add a new soil stack where the en-suite will go.This would also give us the opportunity to tidy up some existing ugly waste pipes that run across the side of the house.

I’m wondering what would be the best way to go? 

Pros for using the existing stack is there is no need for ground work. But being cast iron I’m unsure if it is even possible, and may need replacing with a plastic one? Could this be an option, replacing with a plastic stack above ground level?

Pros for a new connection would be neatness, opportunity to move a ground floor wc in future to improve the layout. But would involve digging up a rather thick concrete path, so much more work and cost.

We are on a combined drainage system (Edwardian house) if that affects anything.

I will be diy-ing the en-suite, but I would prefer to get someone into make the soil stack connections, and ideally leave me with the stack pipe ready for me to connect into. I’m not sure if it would be a general plumber or a ground worker who would do this?

As always, all and any thoughts are welcome. I am just in the planning stage, nothing is set in stone yet.

stuart45

Above ground level is the plumber's job. Below is groundwork.
Traditionally, drainage was the bricklayer's work, as manholes were brick, and the joints in the pipes were sand/cement. Nowadays, drainage is often done by groundworkers, or drainers.

Section62

ChasingtheWelshdream said:

Pros for a new connection would be neatness, opportunity to move a ground floor wc in future to improve the layout. But would involve digging up a rather thick concrete path, so much more work and cost.

If this means you could have an internal stack which will ultimately be in a cloakroom etc (i.e. out of sight, rather than in the middle of the lounge) then I would tend towards having the new stack but putting it on the inside of the property rather than outside (making use of an air admittance valve if allowed).

More work with the path digging up (and taking the drain through the foundations), but a much better result in terms of functionality and tidiness.

ChasingtheWelshdream

Thank you both.

I don’t think it could go internally as there is a chimney breast in the way which I think would make other connections difficult, but definitely worth a look.

The downstairs loo is currently off the utility room, off the kitchen and it bugs me. I would love to move both so they come off the hall way, and reconfigure the kitchen but this involves knocking down a very hefty wall, so is unlikely to happen anytime soon (despite my fantasies). But whether to future-proof is well worth considering.

If we went for the -presumably - cheaper option of using the existing stack, is it possible to connect into cast iron? Years ago we had a plumber look who said they wouldn’t touch it, but no reason given.

FreeBear

There is potential to crack the cast iron pipe as it is being cut for a new connection. Although you can get CI pipes & fittings, they are expensive. You could replace some of the existing CI stack with plastic, but the joint would be pretty ugly - An option if you want to defer groundworks and keep the costs down. That said, you'll probably find the CI stack is cemented it to a clay socket just below ground level, so if you can get to that joint, replacing the whole stack would be easier.

stuart45

ChasingtheWelshdream said:

If we went for the -presumably - cheaper option of using the existing stack, is it possible to connect into cast iron? Years ago we had a plumber look who said they wouldn’t touch it, but no reason given.

It can be done, although you might have trouble finding a plumber who wants to do it. You have trouble even finding a plumber.

Apodemus

Section62 said:

ChasingtheWelshdream said:

Pros for a new connection would be neatness, opportunity to move a ground floor wc in future to improve the layout. But would involve digging up a rather thick concrete path, so much more work and cost.

....I would tend towards having the new stack but putting it on the inside of the property rather than outside (making use of an air admittance valve if allowed).

....a much better result in terms of functionality and tidiness.

s62, that's interesting.  I can see the benefits in terms of tidiness, but what's your thinking on functionality?  I've seen problems with internal air admittance valves but not with external soil stacks, so I would have thought that an old-fashioned soil stack was preferrable from the point of view of functionality?

Section62

Apodemus said:

Section62 said:

ChasingtheWelshdream said:

Pros for a new connection would be neatness, opportunity to move a ground floor wc in future to improve the layout. But would involve digging up a rather thick concrete path, so much more work and cost.

....I would tend towards having the new stack but putting it on the inside of the property rather than outside (making use of an air admittance valve if allowed).

....a much better result in terms of functionality and tidiness.

s62, that's interesting.  I can see the benefits in terms of tidiness, but what's your thinking on functionality?  I've seen problems with internal air admittance valves but not with external soil stacks, so I would have thought that an old-fashioned soil stack was preferrable from the point of view of functionality?

Sorry, I meant 'functionality' primarily in terms of having the new stack ready for the downstairs WC... i.e. the extra cost of extending the drainage is worth it because you can potentially do more with that  than just connecting the en suite.

The internal vs external is primarily about tidiness, although a downstairs WC will need some kind of opening made through the wall and on the whole I'd prefer to go down first, rather than having a hole through the wall just above damp level.  All subject to the existing drain being deep enough, and compliance with regs.

plumb1_2

Fairly easy to T into cast iron, 9” grinder and ensign clamps to to join together. Fitted loads in commercial buildings due to fire regs.
Timesaver cast iron, but expensive.
Best to change to plastic, cut stack about 100mm above floor finish, cast to plastic adapter, then a rodding eye branch the off you go.

ChasingtheWelshdream

stuart45

It can be done, although you might have trouble finding a plumber who wants to do it. You have trouble even finding a plumber.

plumb1_2 said:

Fairly easy to T into cast iron, 9” grinder and ensign clamps to to join together. Fitted loads in commercial buildings due to fire regs.
Timesaver cast iron, but expensive.
Best to change to plastic, cut stack about 100mm above floor finish, cast to plastic adapter, then a rodding eye branch the off you go.

Thank you both.

I have begun to accept that I will probably never be able to achieve our ideal layout. With a long-term renovation we are short on funds and doing things piecemeal. Living in an unfinished house for 6 years is starting to take its toll so my comments about changing the wc later are probably pie-in-the-sky. 

This en-suite is my last must-have, again being done by me over a long period, and I think we will probably need to make savings where we can. The soil stack may be one of those, so it is good to know it should be possible.

I imagine it would be a fairly hefty job to take it down with the weight, so that would need some thought. I guess cut into sections and rig up some kind of rope system. Some cast iron down pipes need replacing on another elevation this year so will have to do the same thing. Meh - I’m a bit too bleary-eyes to think of details this morning!

As always, thank you both.