Open the walls in an older Central Pennsylvania house and you can sometimes see 100 years of plumbing in about ten feet.
A cast-iron drain disappears into the floor.
There’s a piece of lead coming off it.
Someone added copper in the 1960s.
There’s CPVC from a remodel in the 1990s.
Then somebody tied PEX into that 15 years ago.
None of that is particularly unusual. Plumbing systems don’t usually get replaced all at once. Houses get bathrooms added, kitchens remodeled, water heaters moved and leaks repaired. Every generation leaves something behind.
Understanding what those materials are — and how we’re supposed to connect new plumbing to them — is a big part of remodeling an older house.
When people say “plumbing,” they’re usually talking about two separate systems.
Supply piping brings pressurized hot and cold water to your faucets, showers, toilets and appliances. DWV piping — drain, waste and vent — carries wastewater out and allows the drainage system to breathe. They’re completely different jobs.
| Material | Usually found in |
|---|---|
| Copper, CPVC, PEX | Water supply |
| Cast iron, ABS, PVC | Drain, waste and vent |
| Lead | Unfortunately, several things |
And depending on the age of the house, we can find combinations of all of them.
Cast iron was used extensively for drain, waste and vent systems. And honestly, it has some good qualities. It’s heavy. It’s solid. It’s quiet. Run a toilet through cast iron and you hear considerably less water moving through the walls than you typically do with plastic drain pipe.
The problem is that cast iron doesn’t last forever. Over decades it can corrode internally, develop scale, crack or deteriorate badly enough that sections need to be replaced.
We’ve opened old houses where the cast iron is still doing its job just fine. We’ve opened others where you start wondering what’s actually holding the pipe together.
Age alone doesn’t tell you whether it needs to go. Condition does.
This happens all the time in remodeling. Maybe we’re adding a bathroom and the existing main stack is cast iron. We’re probably not replacing 30 feet of perfectly usable pipe just because the new bathroom is being piped in PVC.
Instead, we make a proper transition. That’s where the rubber transition couplings most homeowners know by the brand name Fernco come into the conversation.
The exact coupling matters. Different pipe materials and diameters don’t always have identical outside dimensions, and some applications call for shielded or specifically listed transition couplings rather than just grabbing a rubber sleeve off the shelf.
The principle is simple: old and new plumbing can absolutely coexist. The transition between them has to be made correctly. That’s a theme you’ll see throughout this entire article.
Go back far enough and you’ll eventually encounter lead. It was used in old plumbing systems, including portions of drainage systems and water-service piping. You’ll sometimes find a lead drain serving an old tub, sink or toilet connected into cast iron.
Lead is soft. You can physically deform it. That’s one reason plumbers could make some pretty unusual connections with it in old houses. It also means that when we’re remodeling around it, we’re dealing with a material from a completely different era.
For drinking-water plumbing, lead is obviously something we take seriously. Pennsylvania’s Plumbing System Lead Ban took effect on 6 January 1991 and applies to plumbing construction and repairs done after that date, wherever the plumbing provides water for human consumption.
Finding old lead doesn’t mean we’re going to start cutting everything out of the house without a plan. But we need to identify what it is, what it’s serving, and whether it makes sense to leave it.
Copper is probably the material most homeowners associate with “good plumbing.” For decades it was the standard choice for residential water distribution, and there’s a reason. Properly installed copper is durable, clean and proven. I’ve opened plenty of houses with decades-old copper that’s still perfectly serviceable.
But copper isn’t indestructible. Water chemistry matters. Pipe thickness matters. Installation matters. Copper can develop pinhole leaks and corrosion, and freezing can obviously damage it. It’s also relatively expensive and labor-intensive compared with modern PEX systems.
That doesn’t make copper obsolete. Good copper is still good plumbing. If we’re remodeling a house with a sound copper system, I’m not interested in replacing it simply because something newer exists.
PVC is the white plastic pipe most homeowners recognize, commonly used for modern drain, waste and vent piping. Compared with cast iron it’s lightweight, easy to cut, easy to assemble and much easier to work with during residential remodeling. It also doesn’t rust — a pretty significant advantage for something whose entire job involves carrying water.
But PVC has different characteristics from cast iron. It’s noisier. It expands and contracts differently. It needs proper support.
And just because plastic pipe is easier to install doesn’t mean anybody with a saw and a can of glue knows how to build a drainage system.
Pitch still matters.
Venting still matters.
Fitting orientation matters.
Sizing matters.
The water doesn’t care that the pipe looks nice. It still has to drain.
ABS is the black plastic drain pipe you’ll sometimes find in existing houses. Functionally it filled much of the same role as PVC in drain, waste and vent systems. We don’t generally use it for our new residential plumbing work, but we absolutely encounter existing ABS during remodels.
And that’s where things get interesting. PVC and ABS are different plastics. You don’t just grab ordinary PVC cement and glue one directly into the other.
Where a transition is needed, it has to be made using an appropriate listed method — which can include a mechanical transition coupling or, where permitted for the specific application, an approved ABS-to-PVC transition cement.
This sounds like a tiny detail. It isn’t. A drain connection hidden behind drywall may sit there for decades. You want the person making that connection to understand what he’s connecting.
CPVC is generally a cream or yellowish plastic water-supply pipe. It was used extensively because it was inexpensive, didn’t corrode like metal and was relatively easy to install.
The problem is what happens as some CPVC systems age. It can get brittle. And brittle water piping makes me nervous.
A drain leak is bad.
A pressurized water line failure can dump an enormous amount of water into a house before anybody realizes what’s happening.
Older CPVC can sometimes become brittle enough that working around it becomes its own problem. You’re trying to change a valve or modify a nearby line and suddenly the existing pipe doesn’t tolerate being disturbed the way you expected.
That’s why I don’t like treating old CPVC as though it’s just another piece of modern plastic pipe. If we’re doing substantial work in a house with aging CPVC, I want to think seriously about what we’re leaving behind. Saving a few hundred dollars isn’t much of a win if we’re closing walls around piping we don’t trust.
PEX is the flexible red, blue, white or sometimes translucent tubing you see in newer homes and remodels. It’s cross-linked polyethylene, and for residential water distribution it solved a lot of problems.
It’s flexible. It requires fewer fittings than rigid piping. It doesn’t corrode like metal. It’s faster to install. And because we can often make long continuous runs, there are fewer connections hidden inside walls.
That’s a big deal. Every fitting you eliminate is one less fitting that can eventually leak.
PEX also gives us options in how a house is piped — more traditional trunk-and-branch layouts, or manifold-style systems with dedicated runs to individual fixtures.
Like every material, it still needs to be installed correctly. Proper fittings. Proper support. Protection where it passes through framing. Keeping it away from conditions it’s not rated for. Understanding expansion and manufacturer requirements.
PEX makes plumbing easier. It doesn’t eliminate the need to know how plumbing works.
This is the part homeowners don’t see when they’re looking at the finished bathroom. Suppose we’re adding a bathroom to an older house. The new work might be PEX supply and PVC drainage. Simple enough.
Except the existing water supply is copper.
The branch we’re connecting to has a short section of CPVC from an old repair.
The drain we’re tying into is cast iron.
There’s an abandoned lead line nearby.
And another bathroom upstream was remodeled years ago using ABS.
Now we’re not just installing new plumbing. We’re connecting several generations of plumbing together. That’s where experience matters.
Just because I can connect new pipe to something doesn’t always mean I should.
If we have a perfectly sound cast-iron stack, it may make complete sense to transition into it. Same with good copper. But if we’re standing there with the wall completely open and there’s six feet of badly corroded cast iron or brittle CPVC between our new plumbing and a known-good section? I’m probably going to recommend replacing it while we have access.
Because access is expensive. The cheapest time to replace questionable plumbing is usually when the wall is already open. Closing everything up and coming back two years later means demolition, repair, paint and potentially damage to whatever we just built.
That’s how a $500 decision becomes a $5,000 problem.
I’ve seen good materials installed badly. I’ve seen old materials installed beautifully. And I’ve seen plumbing systems that look like five different people worked on them because five different people probably did.
The pipe itself matters. But so do sizing, pitch, venting, support, connections, accessibility, protection, and understanding where the system goes next.
That’s why I don’t automatically say “copper good, plastic bad,” or “PEX good, copper old.” That’s not how houses work. The right material depends on what we’re doing, where we’re installing it and what we’re connecting to.
This is particularly relevant around Sunbury, Selinsgrove, Lewisburg, Northumberland, Danville and the older towns throughout the Susquehanna Valley. We’ve got houses that have been standing for 80, 100, sometimes 150 years.
They weren’t frozen in time. They evolved. Indoor plumbing was added. Bathrooms moved. Kitchens changed. Water heaters changed. Municipal utilities arrived. Additions were built. Previous owners remodeled things. The plumbing system evolved right along with the house — the same way the wiring and the walls did.
Pennsylvania’s Uniform Construction Code applies statewide, but more than 90% of Pennsylvania municipalities have elected to administer and enforce it locally — so the exact requirements for a particular project ultimately need to be verified with whoever is handling that job.
This is probably the point I want to end on. Older doesn’t automatically mean bad. Newer doesn’t automatically mean better.
I’ve seen old copper I’d trust without thinking twice. I’ve seen newer plumbing I wouldn’t want hidden behind my own drywall.
When we’re remodeling an older house, the question isn’t “what year was this pipe invented?” The questions are:
Sometimes the answer is leave it alone.
Sometimes it’s make the proper transition and keep going.
And sometimes it’s: we’re already here, the wall is open, replace it now.
Knowing the difference is a big part of remodeling an old house correctly.
On the Sunbury bathroom the walls were open in a house old enough for all of this, so the supply lines and the waste stack were run new from the basement rather than tied into whatever was there. On the Northumberland basement suite there was no drainage under the slab at all — every line had to be saw-cut in and trenched by hand.
Fifteen minutes on the phone. You’ll have a realistic range before we hang up — and if we’re not the right people for it, I’ll tell you.