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g/plumbing • Posted by u/pipefitter_pat •

Cast iron stack replacement in an occupied 1920s four-flat — sequencing question Install

Four-story walkup, single 4 inch cast stack serving four units, original 1926 pipe, failing at the hub joints on the second floor. Owner wants it replaced. Tenants stay in place.

Plan is to open the chase floor by floor, replace with no-hub cast (not PVC — the owner cares about noise and I agree with him), and reconnect each floor's branches as I go.

The part I am still turning over is water service continuity. Every unit loses drainage while its floor is open. Best case that is one day per floor.

Anyone done this occupied? How did you handle the tenant side of it, and did you work top down or bottom up?

💬 6 replies

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u/drain_dave •

Top down, always. If you work bottom up, every floor above you is still using the stack and you are working under a live drain. Top down means the section you are cutting has nothing above it.

Yes it means the top floor tenant is out of drainage first and for the longest cumulative time. Compensate them, that is cheaper than the alternative.

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u/elevator_ernie •

Not a plumber, but I do a lot of occupied-building work and the tenant side is most of the job. What has worked for me:

Written schedule to every unit a week ahead with specific dates, not "sometime next month." A single phone number that is a person, not a company line. And a daily end-of-day note under each door saying what happened and what is next.

The work being disruptive is fine. Tenants tolerating disruption depends almost entirely on whether they feel informed. Every complaint I have ever gotten traced back to surprise, not inconvenience.

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u/pipefitter_pat OP •

That is genuinely the most useful reply in the thread and it has nothing to do with pipe. Stealing the end-of-day note.

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u/medgas_marcus •

Agree on top down and on no-hub over PVC in a residential stack. A PVC stack in a 1926 building will make every flush in the building audible in every unit, and you will hear about it for a year.

One thing: no-hub couplings need proper torque and the shielded ones need the right band. On a vertical stack the coupling is carrying shear, not just sealing. Torque wrench, 60 in-lb, every band.

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u/pipefitter_pat OP •

Planning on the heavy-duty shielded couplings throughout for exactly that reason. Standard bands on a vertical stack in an old building with settling is asking for it.

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u/osha_omar •

Occupied building, open chase, four floors — make sure your floor penetrations get temporary firestopping at the end of every shift, not at the end of the job. An open chase in an occupied residential building overnight is a chimney. The AHJ will care and so will your insurer.

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