Rerouting external soil pipe, removing old cast pipes & joining into cast soil - Best option?

[doogyscoot]

Hi all, hoping I can gain from your wealth of experience. We're getting the whole house rendered at some point reasonably soon and I'd like to sort out the mish-mash of pipework on the back wall while we're at it. Access to underfloor space is possible but its a bugger to get into so would rather keep as much work on the outside as possible.
There are some sections of old cast pipe which go through the wall (at 3 points highlighted in image below) where the bathroom is but they are all now defunct. At some point, someone has put the soil into PVC and brought it through the wall in a new place, offset from the old cast soil pipe then connected to the old cast soil pipe in a rather dodgy looking manner. All the other waste pipes from the bathroom run into this under the floor so no cast pipe is actually doing anything.
There is also a soil pipe from the loft conversion bathroom which runs in a rather unsightly route that we want to re-route and renew. It doesn't seem to incorporate a soil vent (unless there is an air admittance valve in the eaves that I didn't notice).
My ideal solution is remove all cast pipework and replace both it and the existing pvc with new black PVC soil pipes with a tidier route. Also want to cut the cast soil pipe closer to the ground so only the black PVC can be seen before it ties into the cast bit.
I think the renderer is happy to do the section of gutter downpipe but I think I need to sort the soil pipe.

The main queries I have are as follows and I would be very grateful for your opinions/advice:

Any tips in general for dismantling cast pipe joints?

What should I do to remove the old cast pipe that goes through the wall? Just smash away anything that's left with a lump hammer and fill with brick offcuts & cement?

Whats my best option for layout of the junction of the downstairs soil pipe and upstairs soil pipe above where they will have to join into the cast soil pipe? (I have added a few pics of options and notes below. Please suggest any better ideas or suggest which you think makes most sense.)

Best method of cutting cast pipe (I have a 4" and a 6" angle grinder, any particular discs?)

What is the best way to connect the 110mm PVC to the to the cast soil pipe at the ground without restricting flow?

In this option, the downstairs soil pipe would tee straight into the side of the upstairs soil pipe as it comes out of the wall through a swept tee, instead of coming out through an elbow and going down. I am not sure whether the tee joint would be a problem in terms of flow where the two pipes meet but it seems the tidiest option?

In this option the downstairs soil would come out of the wall and go diagonally down to the line of the existing soil pipe, a vertical section would go down to the cast pipe with the upstairs soil teeing in before the cast/PVC joint.

in this option, the downstairs soil pipe continues directly down to tee into the top of the horizontal run of the upstairs soil pipe then there is an elbow above the joint between PVC and cast pipes.

 

[Hugh Jaleak]

If the old stuff is going for scrap, then I wouldn't mess about trying to cut it up, a lump hammer will soon sort it out, but protect yourself with suitable gloves, clothing and face protection. (This is your last pair of eyes!) Knock the sections out through the wall and make good with bricks and mortar, doesn't have to be pretty if the new rendering is going to cover it.

Personally, I'd dig down a bit where the cast goes into the floor, chances are it connects to a salt glazed drain just below the surface. This can be carefully cut with an angle grinder and stone disc, remove clay to cast joint, then use a suitable coupling on the cut spigot end to go straight to plastic. The stack can be replaced in 110mm straight up from there. I'd be inclined to keep the existing pipework layout though, ideally you dont want the discharge from the upstairs WC falling too great a height before hitting the bend. Do likewise with the rainwater pipe, fit an adaptor to 68mm downpipe and carry on from there up with 68mm rainwater downpipe.

Looks like your stack may vent out the roof, vent pipe between the L/H and middle left Velux window?

 

[doogyscoot]

If the old stuff is going for scrap, then I wouldn't mess about trying to cut it up, a lump hammer will soon sort it out, but protect yourself with suitable gloves, clothing and face protection. (This is your last pair of eyes!) Knock the sections out through the wall and make good with bricks and mortar, doesn't have to be pretty if the new rendering is going to cover it.

Personally, I'd dig down a bit where the cast goes into the floor, chances are it connects to a salt glazed drain just below the surface. This can be carefully cut with an angle grinder and stone disc, remove clay to cast joint, then use a suitable coupling on the cut spigot end to go straight to plastic. The stack can be replaced in 110mm straight up from there. I'd be inclined to keep the existing pipework layout though, ideally you dont want the discharge from the upstairs WC falling too great a height before hitting the bend. Do likewise with the rainwater pipe, fit an adaptor to 68mm downpipe and carry on from there up with 68mm rainwater downpipe.

Looks like your stack may vent out the roof, vent pipe between the L/H and middle left Velux window?

Hi Hugh, thanks for the advice about the cast to clay junction under the ground. I wouldn't have thought to dig down so I'll have a look. When you say knock the cast sections out through the wall, do you mean to go under the floor, break it up and knock it out from the inside? That makes sense... I'd been wondering how I'd dislodge it from the wall from outside.

I'm keen to run the pipe across at the bottom so I can access the rodding points without hanging off a ladder, and also because we will eventually be building a raised deck against that wall so it will hide the horizontal run. I hadn't thought about there being an issue with soil falling that far down though. Do you know if there is any guideline on the max vertical drop on a soil pipe? I could maybe put an S in it half way down it it's going to be a problem. The vent you see in the roof is for the bathroom extractor, pretty certain it's not for the soil stack.

The whole rainwater pipe is being replaced with PVC so that shouldn't need to be adapted to cast.

Thanks, Dougie.

 

[TicTac]

If you break the cast iron, you can end up with bits of stack going down the drain and causing a blockage, so it might be best to dig down and cut the salt glazed pipe first.

You've got two down pipes coming off the roof, but the one on the right also has an outlet from a sink, so if the down pipes are going into the surface water, that's a no no, so you'd need to route the sink back into the soil pipe. But where is the stack being vented to. As the roof looks as though it's been converted, it might be best to put in an external AAV, and the BCO may let you put it just above the toilet outlet. Otherwise you could convert to a 40mm pipe, and route it along under the guttering to the gable end, but it's possible that they've put an internal AAV in the roof space when they converted the loft.

An angle grinder with a metal blade will cut off the fixings to the wall.

 

[doogyscoot]

If you break the cast iron, you can end up with bits of stack going down the drain and causing a blockage, so it might be best to dig down and cut the salt glazed pipe first.

You've got two down pipes coming off the roof, but the one on the right also has an outlet from a sink, so if the down pipes are going into the surface water, that's a no no, so you'd need to route the sink back into the soil pipe. But where is the stack being vented to. As the roof looks as though it's been converted, it might be best to put in an external AAV, and the BCO may let you put it just above the toilet outlet. Otherwise you could convert to a 40mm pipe, and route it along under the guttering to the gable end, but it's possible that they've put an internal AAV in the roof space when they converted the loft.

An angle grinder with a metal blade will cut off the fixings to the wall.

Thanks for the advice. The old cast pipe for the sink waste is no-longer used, all of the bathroom waste goes into the soil pipe before it comes through the wall so no waste is going into the down-pipe, only rainwater. The roof is converted, 90s I think and I'm not convinced everything was done as it should have been although the planning docs and completion certificate etc. are all there. The stack is not currently vented anywhere I can see but there may be an AAV in the the eaves that I'm not seeing so I'll have to crawl in there and have a look. If there isn't, would that be the best place to put it? I assume an AAV needs to be located above the height of the toilet pan outlet? If it was external this wouldn't be possible without taking a dog-leg out over the roofline like a normal vent. There hasn't been any issues with siphoning so I assume there must be something. What were you suggesting to convert to 40mm and run along to the gable? A vent?

 

[TicTac]

Toilets are vented to allow both positive and negative pressure to be handled, but an AAV will only handle negative pressure, but as they don't release much smell when they open, they don't need to go above the roofline, just above the height of the toilet itself. You can convert to 32 or 40mm above the toilet etc, as it's only venting.

Find out if the rain water is going into the surface water, or the foul waste drains.

 

[Hugh Jaleak]

Any AAV needs to be above the spillover level of the highest appliance, (usually the basin), so bear that in mind when planning things. Ideally would be better vented, but breaking through the roof isn't for the faint hearted, so an AAV should be ok.

There is no maximum height for a stack, although rules on connection lower down change when you go over 3 storeys. (It can get messy in tower blocks, if the drain blocks, and the upper floors keep discharging, then the ground floor gets it.....) Ideally, you dont want any bends in the wet section of the stack, (only a long radius bend at the bottom where it turns to travel along the drain), but in certain situations it is unavoidable. I'd stick with the minimum number possible, if you can get the bend under the decking it may help with noise deadening when someone flushes above.

As for removing the old cast, whichever way is easiest, but good tip there from TicTac about preventing any shards going down the drain.

 

[doogyscoot]

Thanks to both of you. I'll see if there is an AAV in the crawlspace in the eaves where the solid pipe currently comes through from. If not, I'll have a good think about where would be best to fit one. I can get it above the toilet height in the eaves, possibly even above basin height too. I could also potentially get 40mm pipe from the soil pipe up into the attic space above the bathroom by running it along the rafters between the plasterboard and the sarking. From what I understand an AAV can be situated within the roof space? I doubt it'll have to do much as, assuming it is not currently vented, there have been no problems thus far. We are are on a septic tank which is only about 15m away so maybe there isn't much opportunity for positive or negative pressure build up.
I'll keep the length of the vertical drop as short as I can per your advice Hugh, and use a wider swept bend at the bottom. Noise hasn't been noticeable TBH and its only the spare bedrooms by that bit of pipe anyway so I'm not too fussed.
As a last request, would either of you happen to have any views on which option is best for bringing the pipes together between the downstairs and upstairs soil junction? The first would look best but I don't know if the tee would be an appropriate way of joining into the horizontal run. The third option seems the next best if that is an issue.

 

[Hugh Jaleak]

Join the two soil connections however you find easiest, however the 3rd option is probably my preference of the 2. Bear in mind, any existing fittings are unlikely to be able to be reused, as the seals will have gone hard, and are unlikely to reseal onto new pipework. I'd allow for redoing the pipework to the ground floor WC, back through the wall to the pan, which should also give you some flexibility on how you want to connect it up to the run from upstairs.

 

[TicTac]

Hang on Doogy, is there a toilet in the loft; sorry if I've only picked that up on the last post. Because those cast pipes are so old, I assumed (naughty of me) that the soil pipe going into the eaves was for venting, not for waste. As Hugh has said, if you have too much of a straight drop, it can cause issues, and that could be why they've put a slight kink in the down pipe just before the lower outlet. If I'm right, on the upper toilet, then post some picture of the bathroom/s.

 

[doogyscoot]

Join the two soil connections however you find easiest, however the 3rd option is probably my preference of the 2. Bear in mind, any existing fittings are unlikely to be able to be reused, as the seals will have gone hard, and are unlikely to reseal onto new pipework. I'd allow for redoing the pipework to the ground floor WC, back through the wall to the pan, which should also give you some flexibility on how you want to connect it up to the run from upstairs.

Thanks again for the advice. I'm hopeful that the elbow through the wall into the downstairs bathroom is socketed at each end and I can just attach the socket of a new elbow to the pipe which is coming through the wall, I'll do a wee recce under the floor to try and figure it out. The rest of the pipe and fittings are being replaced anyway as it's going to be done in black to match the downpipes... currently trying to decide if it's worth paying double the price to get floplast pipes or just get the cheap unbranded ones off the internet.
Anyway, I also had a wee crawl along the eaves tonight and discovered that there is in fact what I assume to be a an AAV in the eaves situated above the height of the basin overflow so that's one thing less to sort out.

Hang on Doogy, is there a toilet in the loft; sorry if I've only picked that up on the last post. Because those cast pipes are so old, I assumed (naughty of me) that the soil pipe going into the eaves was for venting, not for waste. As Hugh has said, if you have too much of a straight drop, it can cause issues, and that could be why they've put a slight kink in the down pipe just before the lower outlet. If I'm right, on the upper toilet, then post some picture of the bathroom/s.

Thanks for the input TicTac, yes, there is a bathroom in the attic conversion, but as above, have found that it is properly vented. Didn't think to take a pic of the bathroom but the pipe runs under the floor to the eaves. It's a yet to be done part of the refurb, so while functional, isn't quite done. I've seen quite a few double story houses with soil pipes dropping that far or more without a bend so I think I'll chance it. I considered a 112.5 deg elbow to run a steeper fall on the horizontal section to encourage flow and allow a higher joint to the vertical section but think I'll stick with 92.5 deg. I'm pretty sure the kink in the existing pipe is just to allow the pipe to get around the window.

 

[Hugh Jaleak]

Personally I'd go with Floplast, buy cheap, buy twice. It's something that is going to be in use for a long time, and needs to work properly!

 

[doogyscoot]

Sorry to bother you again but I've dug down to the joint and found where the cast pipe is mortared in as suggested. I was hoping you could help clarify the process/fittings required to connect into what I think is a salt glaze pipe. The cast pipe seemed able to wiggle a bit at the joint and the rest of the concrete/cement around the top was reasonably soft and came away quite easily so I'm reasonably hopeful I should be able to remove the cast from the salt glaze spigot without destroying the spigot. Plan is to use a drill to gently break up the cement with a shop vac to suck away the debris as I go.
I was trying to figure out what connector I should use to go from PVC straight into the salt glaze spigot. I've seen a few from different companies and not sure which I should be using or even exactly how they fit. I will buy a rubber boot connector with jubilee clips anyway, just in case the spigot cracks and I have to cut it off but would rather avoid this as it means digging a much bigger hole to get at it with an angle grinder. Once again, I would appreciate advice on anything that can go straight into an undamaged salt glaze spigot and the related process. Here are a few fittings I've found, amongst many:

https://www.drainagesuperstore.co.uk/product/pvcu-to-cast-iron-and-salt-glaze-drain-connector-black.html
https://mcalpineplumbing.com/plasti...nectors-roof-flashing/dc1-blc-drain-connector
http://www.topline.ie/plumbing-heat...um-pvc-sewer-pipe-to-s-g-spigot-adaptor-110mm
https://www.mytub.co.uk/110mm-adaptor-to-sgs-socket-ua41-product-560623

Also Can I just confirm something about the last image, the connection between the elbow and the 45deg section looks like a spigot to a spigot? I'm assuming this is just a bit of a bodge and they have used a small section of pipe to allow two spigots to but like this? Or is it some other method of coupling I'm not aware of?

Thanks again.

Thanks again.

 

[denso13]

Or is it some other method of coupling I'm not aware of?

That's fine, just a bit of pipe between the sockets as you suspect.

 

[Hugh Jaleak]

From your list, either go for the McAlpine DC-1, that'll fit inside the pipe neatly, (and avoid the need to cut anything hopefully), or you can use either of those fitting from DrainSuperstore or Mytub. These both fit in a salt glazed socket, and require you to finish the joint with mortar to seal and retain the fitting.

The Wavin fitting you've found may be for 100mm Vitrified Clay pipes, such as Hepworth Supersleve, which is a thinner outside diameter than the salt glazed stuff, I would avoid this one as may not fit!

You may find that mortar joint is very soft and will dig out with a suitable tool quite easily. The salt glazed can be very fragile, I'd avoid putting any stress on that drain if you can at all help it.