cacked cast iron soil vent pipe

[bobby spray]

Hello, I have a cracked cast iron soil vent pipe (3 1/8" i think). The cracked section is near the bottom of the stack. the very bottom section is concreted into some stairs so cannot come out. I have scaffolding up at the moment so the opportunity is there to replace the corroded section. The pipes are sealed with lead and (oakum?) How should I go about repairing this? There are five 6ft lenths above the cracked section. Do I need to take the whole lot down? or can I cut out a section (angle grinder?) and just replace that? The building is listed so I can't replace with plastic or aluminium.

Bobby

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IMG00483-20110911-095511 by berettaboy, on Flickr[/img]

 

[tim00]

Read this post from : mnb, feb 23 2006, "replacing or cutting into a cast iron soil stack". Safety, safety.

Given you have a listed property then you will probably have to replace like with like. That is, no plastic or no-hub fittings allowed. You must replace with traditional hub and spigot, poured lead joins. Traditionally, ironwork has been painted black.

Also, given the state of the in-situ stack, then replace the whole thing. You might find that the upper stack, the vent, is paper thin. Note that replacing a stack will involve going thru the wall to re-connect to WC's, and all waste conn's must be taken into account.

Regarding the base of the stack entering concrete steps, post some pics, in fact post more pics of the whole arrangement.

Do you have a second, detached WC? Have you located the nearest man hole? Dont try and slide by the listed bldg demands - they almost certainly will catch you if you do, and the consequencies could be an expensive detailed inspection of the whole property. Contact them and discuss.

 

[bobby spray]

Here is a pic and schematic of the whole arrangement. There is only one toilet connected to this stack. and it's below the stairs for the basement flat. I cannot get to the bottom of the stack as it's under 6' of concrete.

I checked to upper stack right at the top (above the roof line) and it's sound. My worry would be that the stack would come down if I removed one section as it only is ties to the wall with hooks. I obviously can't replace the very bottom section. So I'll have to carefully break the joint. how easy is it to dismantle using heat to melt the lead?

 

[tim00]

I still persist, the stack is on it's last legs. Feel behind the stack, where it typically is not painted, and you will probably find rust and fragility.

Do not attempt to cut the obviously damaged lower section out: there is the safety consideration of the upper stack dropping, or debris dropping down the stack and blocking the slow bend at the base.

The hooks merely hold the stack in to the masonry, they do not support it. Any work would req. supporting
clamps to be bolted into the masonry before work commenced.

I hesitate to give detailed descriptions of what you ask for, sheer building experience is req'd, and professional eqpt. But something must be done soon - the stack could crumble on you at any time esp. with building work around it.

Talk to the authorities, maybe the majority of the stack could be dropped and an AAV could be installed?

Once again, i suggest that you carefully read the 2006 post and consider what what you propose might involve.

 

[tim00]

Further, i'm puzzled ref your use of "listed". Is it listed with Historic Scotland or is it a local planning kind of "listing"?

 

[joe-90]

You can make a quick easy fix with a fibreglass kit from Halfords or other motor factors. In my experience the damage is usually localized.

 

[bobby spray]

I suspect that the damage is indeed localised. Looking at some other cast gutter I have replaced which is the same vintage as the stack (1895) the thickness seems to vary considerably from section to section. I recon the old sand cast moulds weren’t up to much. I Plan to cut down the stack as far as the corroded section and replace. I’ll caulk and lead the joints (should be fun) as it’s only a vent pipe.
Yes the building is listed with Historic Scotland (B listed)

 

[tim00]

If you cut the stack down, then cut to the lowest possible stub. The logic of leaving in a length of 1898 pipe defies me.

With respect, do not use any quick and easy fibre glass wrap. There are, say, two tons of cast iron above, with no ears or clips, hence all the weight is on the weakest point. Never use fibre glass to repair cast iron pipe or guttering.

You suspect the damage is localised, but you dont know for sure. Go ahead and remove the stack as you now propose.

I asked you a number of Q's but only received a couple of answers. Whereas you asked Q's and received many answers. Good luck to you.

 

[joe-90]

Two tons? What planet are you on then? Oh and they only ever get a small area at the back that never gets painted and rusts out. This is a DIY site - cheap fixes not repairs costing silly money. If it was as bad as you think it is it would have collapsed years ago.

 

[bobby spray]

Tim, sorry if you feel I missed your questions. I respect your advice. The fitting of the AAV is not allowed as getting rid of the stack would change the appearance of the building as as I said it's B listed. I did read the link to the other post. most helpful. I have estimated the weight of the stack to be 5 x 60 kg (per six foot length) so nowhere near a ton. I can attach this with ties to the scaffolding at intervals.

I had a closer look at the cracked section today. I scraped off the paint and it looks to me like the section is cracked. no holes or corrosion on the outside. I suspect that the crack may be due to impact damage rather than corrosion. as it's (the crack) is long and thin.

as far as leaving the older section. I agree. Not ideal but I will have a look at it once I have taken the section above off. The alternative is to break up four feet of concrete.

regards

BS

 

[jabuzzard]

The problem is that you cannot replace a section in the middle. The whole lot has to come down to the point where there is a problem and then you go back up again. There is just no play in a cast iron pipe to work a new pipe in the middle if you are going with traditional jointing.

Given the age of the building I would seriously consider replacing the lot. Modern stuff is much better quality believe it or not as the casting methods give consistent results and the insides are coated with epoxy paint. Also it will be a standard 2", 2.5", 3" etc. size as it will all be to BS416.

You might want to check out whether Heritage Scotland would be happy with using Timesaver Heritage. Looks just like traditional BS416 but is mechanical push fit so you can replace sections in the middle. It was not an option for me as I have a 3.5" soil pipe, so had to take the whole lot down and put back up to replace a damaged section at the base. Oddly on mine the vertical joins where done in oakum and cement, with only the "horizontal" joins done with lead.

Finally remember unless stripped at some time in the past the base layers of paint will be lead based.

 

[xr4x4]

Clean the area up, grind it down. Repair with chemical metal or a welder to weld the crack or weld a plate on. Filler to tidy up if ness and paint.