Behind most pre-war Portland kitchens there’s a pipe nobody has looked at in a hundred years. It carries everything from the sink and dishwasher down to the sewer, it’s made of cast iron, and it usually gets attention in one of two ways: a slow drain that keeps coming back, or a plumber looking at it with the sink cabinet pulled out.
This post covers where that pipe is, how it fails, how to find out what condition yours is in, what your options are, and what the Portland plumbing permit does and doesn’t require. It matters most if you want to move the sink, because the pipe behind it decides how hard that is.
What cast iron drain pipe is, and where it is in your house
From the early 1900s until the 1970s, cast iron was the standard material for house drains in the United States. It’s heavy, thick-walled and dark, and it’s quiet when water runs through it, which is one reason it stayed the default for so long. Portland’s pre-war bungalows and Craftsmans were built squarely in that period, so the drain system in most houses built before about 1975 is cast iron in whole or in part.
In a kitchen, the pipe that matters is the main stack: a vertical pipe, commonly three or four inches across, that collects waste from the house and carries it down to the sewer while venting up through the roof. The sink drains into it through a shorter branch. That branch is often not cast iron. In a house that has been worked on over the decades it can be galvanized steel, or have been replaced with plastic at some point, so it’s common to find a mix: original stack, original branch, and a repair from the 1980s joined to both.
Older cast iron is joined at hubs sealed with lead and oakum. Later systems use no-hub pipe held together with rubber-and-steel clamp couplings. Both are visible once a wall is open, and the joint is often where the trouble starts.
How cast iron drains fail, and why it’s usually slow
Cast iron mostly fails slowly, and from the inside. Waste and moisture corrode the inner wall and build up a layer of scale that narrows the pipe and leaves a rough surface. A kitchen drain carries grease and food solids, and a rough surface catches them. Joints loosen or shift as a house settles. Eventually a section can crack or leak at a joint, and on a badly corroded pipe a section can fail outright.
How long it lasts has no single answer. Commonly cited estimates run from about 40 years to well over 100, and that range tells you how much depends on the individual pipe: its quality, the water, how it has been used. Age alone doesn’t tell you much. Condition does.
Signs of trouble in a kitchen
- A slow sink that comes back after you clear it. One clog is a clog. A clog that keeps returning can be the pipe.
- Gurgling when the dishwasher drains or the sink empties.
- A sewer smell near the sink cabinet.
- Stains, swelling or a soft spot at the base of the sink cabinet, which can mean a slow leak at a joint. Our water damage guide covers what that does to the framing behind it.
- Rust streaks, flaking or pitting on any pipe you can see below the sink or in the basement.
None of these proves the stack is failing. They’re reasons to look.
How to find out what condition yours is in
The reliable way is a camera inspection. A plumber feeds a small camera into the line, usually through a cleanout, a roof vent or a removed fixture, and you see the inside of the pipe: scale, pitting, cracks, joints that have shifted. It doesn’t need a wall opened.
It’s information, not a guarantee. A clean result says the pipe is in good shape today. A rough result tells you what to plan for before you design around that pipe, which is the useful time to know. Please don’t open walls or pull pipe yourself, and if the pipe is suspect, tell whoever is quoting your remodel before they quote it.
Your options, and when each one makes sense
This is how it typically goes. Your plumber and your inspector make the final call on your house.
| Condition | Typical option | Trade-off |
|---|---|---|
| Sound pipe, light scale | Leave it and have the line cleaned | Lowest disruption, but it doesn’t fix corrosion that’s already there |
| Moderate corrosion, walls still solid | Descale the pipe or line it from the inside | Can avoid opening walls; ask whether it suits your stack and is accepted for your permit |
| Cracked, leaking or shifted joints | Replace the affected section with plastic drain pipe, joined with approved transition couplings | Opens the wall or floor, but fixes the actual failure |
| Heavy corrosion through the stack | Replace the stack | The most disruptive option, and the best time to do it is while the wall is already open |
| You want to move the sink or dishwasher | A new branch tied into a sound stack | Cost depends on distance and what’s in the floor; the stack has to be in good condition to tie into |
Why a remodel is the right time, and the wrong time to find out
Opening a finished wall costs money whether or not anything is wrong behind it. If the wall is already open for a remodel, replacing a bad section of drain is a modest addition to work that’s happening anyway. If you wait, you pay to open and close the same wall a second time to do what could have been done once.
The wrong time to find out is partway through demolition. A pipe that turns out to be in poor shape after the schedule and the cabinet order are set forces decisions in a hurry. That’s why we trace the drain at the walkthrough, look at what we can see, and put a line in the quote for it. Where the sink goes in your layout and the condition of the pipe behind it should be decided together. It’s the same conversation as in our kitchen design guide.
What the plumbing permit and inspection actually mean
The same logic as the wiring, and the same careful answer. See how it plays out in our knob-and-tube wiring guide.
Portland Permitting & Development says a plumbing permit is needed to repair, replace, relocate or add to the piping system in your home, and it lists broken sewer and drain lines among the cases (residential plumbing permits). Under Portland City Code 25.05.030 the application names a contractor holding a State of Oregon plumbing contractor registration, with provisions for owners doing their own work. A final inspection closes the permit.
It doesn’t say that pulling a permit for a new sink means every old pipe in the house must be replaced. Pipe you don’t touch isn’t generally re-inspected. What the inspector sees is the new work and what it connects to.
That’s where judgment comes in. If the stack is corroded and the new sink branch has to tie into it, a plumber and an inspector are unlikely to want new work connected to pipe that is failing. In our experience, when a wall is open and the drain behind it is in poor shape, that section gets replaced.
That is common practice, not a blanket rule, and what’s required on your house is decided at your inspection. We tell you that before demo, not after. Our permits guide covers who reviews what and how long it takes.
How your house changes the job
The same pipe is a different job depending on where it runs.
The stack and branch are often reachable from below. This is the easiest case: the pipe can be looked at and, if needed, worked on without opening the kitchen walls.
Common in 1950s and 1960s brick ranches. The drains are in or under the concrete, so moving a sink or adding a dishwasher drain can mean cutting a chase in the slab. We tell you before the layout is fixed. See how this plays out in North Portland kitchens.
Common in two-story pre-war houses, where the stack runs inside a wall between floors. Looking at it takes a camera or an opening. Replacing it can mean opening that wall and the one above or below.
Moisture from the slope can add its own damage near the kitchen drain. Our Multnomah Village page describes how that changes the walkthrough.
How it changes your quote and your schedule
Scope depends on what the stack and branch are made of, what condition they’re in, how reachable they are, and whether the sink is moving. None of that can be priced without looking.
So an honest quote for an older Portland kitchen with a moved sink or a suspect drain has a plumbing line, and a contingency stated in dollars for what’s behind the walls. If a quote on a 1920s house that moves the sink says nothing about the drain, ask why. The gap tends to come back as a change order after demo, when you have the least leverage. Our cost guide explains how we build the number.
On the schedule, the plumbing rough-in has to be inspected before the walls close, and the permit isn’t closed until the final inspection. The timeline guide shows where those steps sit. When we open a wall and the pipe is worse than expected, we stop, photograph it, show you, and get your written approval before the plan changes. You can see how that works in our process guide.
Questions to ask any contractor about old drain pipe
- Will you look at the drain stack and the sink branch at the walkthrough, before quoting?
- If I’m moving the sink, what’s the plan for the drain, and is it in the quote?
- Do you recommend a camera inspection, and who does it?
- Who pulls the plumbing permit, and who does the work?
- What happens if the pipe is worse than expected, and who approves the change?
More on comparing contractors in how to hire a kitchen contractor in Portland.
Where this comes up most
Cast iron drains are standard in Portland housing built before about 1975, so this comes up across inner SE and NE. We see it in Sellwood-Moreland, Hawthorne, Irvington, Woodstock, Ladd’s Addition and Alberta Arts District.
Frequently Asked Questions
Do I have to replace cast iron drains if I remodel my kitchen?
No. The work follows what you’re changing and what the inspector requires. If the stack behind your wall is in poor shape, or a new drain has to tie into it, replacing that section is common, and the best time to do it is while the wall is open.
Can cast iron drain pipe be repaired or lined instead of replaced?
Sometimes. Descaling and lining are options plumbers offer for pipe in moderate condition. Whether one suits your stack, and whether the city accepts it for your job, are questions for your plumber and Portland’s permitting office.
How long do cast iron drain pipes last?
There’s no single answer. Commonly cited estimates run from about 40 years to well over 100. Condition matters more than age, and a camera inspection is how you see it.
Can I move my kitchen sink in a house with cast iron drains?
Usually yes. The new branch ties into the stack, so the stack has to be sound, and the distance and the floor construction decide the cost. Slab houses are the hard case. The kitchen design guide covers how to weigh it.
Is my slow drain a clog or the pipe?
One slow drain that clears and stays clear is usually a clog. A drain that keeps slowing after being cleared, with gurgling or a smell, points to the pipe. A camera inspection answers it.
Not sure what’s behind your sink?
That’s what the walkthrough is for. At Rainwood Kitchen Craft Co, we trace the drain, look at what’s visible in the basement or under the sink, and say plainly what we can and can’t tell before we write a number. Call (971) 535-8286 or send the form below.