Which pipe to choose when renovating an old building's plumbing

Why an old building's existing pipework complicates the choice

In a building from the 1930s or from the Soviet decades, the pipework was rarely installed to a single standard, and it has usually been patched more than once. You might find galvanised steel risers from the original build, a section of copper added in the 1990s, and a plastic branch line fitted by a previous owner who did a bathroom renovation without touching the rest.

That mixture matters because every join between two different metals, or between old threaded fittings and a modern push-fit system, is a point where things can go wrong: galvanic corrosion between dissimilar metals, a thread that no longer seals against a new fitting, or a wall chase that was never meant to carry a rigid pipe of today's diameter.

The practical result is that the right material for your renovation depends less on which pipe is theoretically best and more on what it has to join to, and how much of the existing system you are actually replacing this time round.

Stainless steel as a continuation of old metal pipework

Stainless steel threads and fits in much the same way as the old galvanised steel it replaces, which is why it is a common choice when you are renewing a riser but leaving neighbouring sections of galvanised pipe in place, particularly in a shared stack in an apartment block.

It resists corrosion well on its own, but the point where new stainless meets old galvanised steel is still a junction between two different metals, and it should be made with the correct transition fitting rather than a direct thread, or you reintroduce the corrosion risk you were trying to remove.

Stainless is heavier to work with than plastic pipe and the fittings cost more, but where the rest of a building's stack is still steel, and where an apartment association wants continuity with what the neighbours have, it is often the pragmatic choice rather than the cheapest one.

PEX and multilayer plastic pipe in an old building's conditions

PEX and multilayer pipe are quicker to install, tolerant of the slightly irregular routing you often find in an old building's walls and floors, and a reasonable choice for branch lines feeding a kitchen or bathroom from a more solid riser.

The complication is at the ends: plastic pipe joins to old brass or steel fittings through a threaded adaptor, and that adaptor is only as good as the thread it is going onto. A galvanised thread that has corroded slightly, or been over-tightened at some point in the building's history, may not seal reliably against a new adaptor without some rework of the fitting itself.

Plastic pipe also should not be built into a wall or floor without a proper conduit or chase that allows for it, and in a building where the original chases were sized for narrower steel pipe, that sometimes means more chasing-out than a straight like-for-like swap would.

Copper on old building risers — when it still makes sense

Copper is the material most old buildings were designed around before plastic pipe became common, and it remains a sound choice for a full riser replacement in a pre-war house, particularly where the building has exposed pipework that is meant to be seen rather than hidden in a chase.

It solders cleanly to older copper sections and joins to brass fittings without the transition concerns that come with mixing metals, which makes it the more forgiving option where you are extending an existing copper run rather than starting from steel.

The trade-off is cost and labour time: copper pipe and soldered joints take longer to install than a push-fit plastic system, and that shows up directly in an hourly quote. Where the budget allows and the existing pipework is already copper, it is usually still the tidiest continuation.

What to check before settling on a material

Before choosing, it is worth having someone open up an access point or two and look at what the existing pipework actually is, rather than assuming from the building's age. Two flats in the same panel block can have had different repairs over the decades.

The checks below are the ones that decide which material will actually work with what you have, more than any comparison of the materials in the abstract.

• What metal, if any, the section you are joining to is made of
• The condition of the existing thread or joint you would be connecting to
• Whether the wall or floor chase has room for the new pipe's outer diameter
• Whether the section belongs solely to your flat or is shared with the stack
• Water pressure and whether the building has a pressure-reducing valve already
• Whether the renovation also touches heating pipework, which may need different fittings again

Where to go once the choice is made

Once you know roughly which material fits your situation, the next useful step is a site visit rather than more research, since the details that decide the final choice — thread condition, chase width, what is shared with neighbours — are only visible in the building itself.

Our plumbing work, from 45 € per hour, covers exactly this kind of assessment and the pipework replacement that follows, including the transition fittings that mixed old-and-new systems tend to need. If the job also involves opening up wall chases, patching plaster, or other work around the pipe run, our odd jobs service, from 39 € per hour, is often booked alongside it.

For anything involving a shared riser in an apartment building, it is worth raising the plan with the korteriühistu before work starts, since a stack often runs through several flats and the association may already have views on the preferred material.