Moving bathroom plumbing & the soil pipe
Sometimes the bathroom you want isn’t the bathroom you’ve got — the bath’s in the wrong place, the toilet blocks the window, or the whole room would simply work better rearranged. The good news is that the basin, bath and even the WC can nearly always be moved. The honest bit is that some moves are simple and some are a proper piece of work, and the toilet is the fussiest of the lot. This guide explains what’s involved in relocating each fixture, why the soil pipe and its falls are the deciding factor, and when moving the plumbing is worth it as part of a full bathroom installation.
Why move the plumbing at all?
Most tired bathrooms were laid out decades ago, often to suit the plumbing rather than the people using the room. Rearranging the fixtures can transform how a bathroom feels and functions — turning an awkward, cramped room into one that’s genuinely comfortable. Common reasons homeowners want to move things include swapping a bath for a bigger walk-in shower in a better spot, freeing up a window, creating room for a double vanity, or reconfiguring an en-suite or cloakroom so it doesn’t feel like a cupboard.
The key thing to understand is that not all moves are equal. Shifting a basin a metre along the wall is straightforward. Moving a bath is a bit more involved. Moving the toilet is the big one, because unlike the others it doesn’t just need a water feed and a small waste — it needs a large-diameter waste run to the soil stack, set at exactly the right gradient, and that’s what governs how far and where it can sensibly go. Understanding this is what lets us advise you honestly on which changes are quick wins and which ones genuinely earn their cost.
All of this work happens at first fix, while the walls and floor are open, which is exactly why a refit is the natural time to do it. Trying to move plumbing without stripping the room out is far more disruptive — so if you’re redoing the bathroom anyway, it’s the ideal moment to get the layout you actually want.
Moving each fixture: what’s involved
Here’s an honest run-through of what it takes to relocate each part of a bathroom, from the easiest to the most involved — so you can weigh up your ideal layout against the work behind it.
The basin — easiest
A basin needs hot and cold feeds and a small (usually 32–40mm) waste. Both are easy to re-route within the room, so a basin can generally go pretty much where you’d like it. It’s the fixture we have most freedom with, and moving it rarely adds much to a job.
The bath or shower — moderate
A bath or shower tray needs feeds and a larger waste, which needs a fall to drain. As long as we can run that waste to the stack at the right gradient, they can move — though the further from the stack, the more careful the routing. In an upstairs room the waste has to hide within the floor depth, which sets some limits.
The toilet — the big one
The WC needs a 110mm soil waste run to the stack, set at the correct fall the whole way. That’s a much bigger pipe than the others and far less forgiving of distance and direction. Moving the toilet is very doable, but it’s the change that most affects cost and feasibility — and it all comes down to the soil pipe.
The soil pipe and why falls matter
The soil pipe is the large waste that carries everything from the toilet to the main soil stack and out to the drains. It’s the single biggest factor in whether — and how far — a toilet can move, and it comes down to one principle: fall. The pipe has to slope continuously downward from the WC to the stack, at a gradient that’s just right. Too shallow and the waste doesn’t clear properly, so it blocks and smells. Too steep and the water runs away faster than the solids, which also blocks. There’s a correct window, and the whole run has to stay within it.
Distance eats height
Because the pipe must keep falling the whole way, the further the toilet moves from the stack, the more the pipe drops over that distance — and that height has to come from somewhere. Downstairs on a suspended floor there’s often room. Upstairs, the pipe has to hide within the floor joists, so there’s a hard limit on how far a WC can travel before the run simply won’t fit. This is why we survey the floor depth and the stack position before promising any layout.
Tying into the stack
The new run has to connect cleanly into the soil stack at the right point, watertight and properly supported, and often vented so the system breathes and traps keep their seal. Get any of this wrong and you get gurgling, slow flushes or drain smells. It’s precise work, which is why moving a toilet is priced as the significant job it is — but done right, it’s completely reliable and invisible.
None of this means “no” — it means we design the layout around what the soil run can actually achieve, and tell you straight if a particular toilet position isn’t sensible. Nine times out of ten there’s a layout that gives you what you’re really after, sometimes with a small adjustment to where the WC sits. The full picture of feeds, wastes and testing is covered in our first-fix plumbing guide.
When gravity won’t do it: macerators & pumps
Occasionally you want a toilet somewhere a gravity soil run genuinely can’t reach — a cloakroom under the stairs, a new en-suite far from the stack, a basement. That’s where a macerator (often known by the Saniflo brand name) comes in. It sits behind the WC, breaks down the waste and pumps it through a small-bore pipe to the stack, so the toilet no longer depends on a big gravity fall. It opens up positions that would otherwise be impossible.
Where a macerator helps
It’s the go-to solution for adding a WC where there’s no practical route for a 110mm soil run — under-stairs loos, loft en-suites, and rooms a long way from the stack. For those projects it’s often the difference between having a toilet there and not, which is why we fit them where they genuinely make sense. It’s a common part of en-suite and cloakroom work.
The honest trade-offs
A macerator is a mechanical pump, so it has moving parts that a gravity pipe doesn’t — it makes a noise when it runs, needs power, and can eventually need servicing or replacing. A proper gravity soil connection is more reliable and maintenance-free where it’s achievable. So our advice is simple: use gravity where you can, and a macerator where you must. We’ll always tell you honestly which camp your project falls into.
This is a good example of where honest advice saves you money and regret: a macerator fitted because it was easier, when a gravity run was perfectly possible, is a maintenance job you didn’t need. We’d rather do the slightly harder pipework once and leave you with something that just works.
Is moving the plumbing worth the cost?
Moving fixtures adds to a bathroom’s price — new feeds, new waste runs, and for the toilet a re-routed soil connection — so it’s fair to ask whether it’s worth it. Our honest take is that it depends entirely on how much the new layout improves the room. Here’s how we’d frame the decision.
- Worth it: when a rearranged layout turns a cramped, awkward room into one that genuinely works — more usable space, a proper shower, a better flow. You live with a bathroom every day; a layout that fits your life pays back in use.
- Worth it: when you’re already stripping the room out, so the walls and floor are open anyway and the extra work is far cheaper than doing it later as a standalone job.
- Think twice: when the existing layout is basically fine and you’re moving things for the sake of it — keeping the plumbing where it is is the single biggest saving on any bathroom.
- Think twice: when a small tweak to your dream layout would keep the toilet near the stack and save a big soil re-route for a difference you’d barely notice.
Because keeping or moving the plumbing is the largest single lever on what a bathroom costs, we always set it out clearly on your fixed quote, so you can see exactly what the layout change is buying you and decide with your eyes open. For the wider numbers, see the cost of a bathroom in Plymouth, and for how a new layout fits a bigger project, our bathroom renovation service.
Planning a new layout that actually works
Moving the plumbing is only half the story — the other half is designing a layout that’s better to live in, not just different. When we survey a room for a move, we’re thinking about more than where the pipes can go. We look at the door swing, the window, the sightline as you walk in, where the light falls, and how two people use the room on a busy morning. A toilet you can relocate isn’t worth relocating unless the new position genuinely improves all of that.
Water supply comes into it too. If your plan puts a big shower in a new spot, we check that your water pressure and flow will actually run it well there, because a beautiful shower on poor pressure is a daily disappointment. And because moving fixtures reshapes the whole first-fix stage, it changes the shape of the job — worth understanding alongside the full installation process so you know how the extra work fits the timeline.
The upshot is that a good layout is a design decision as much as a plumbing one. We bring both to the table: the honest engineering of what the soil run and floor depth allow, and an eye for how the finished room will feel to use. Get those two working together and a rearranged bathroom doesn’t just look better in the plan — it’s a pleasure every single day.
Moving bathroom plumbing FAQs
Can you move a toilet to the other side of the bathroom?
Usually yes, but it depends on the soil pipe. The WC needs a large waste run to the stack at a continuous fall, so the position has to allow that. Downstairs there’s often plenty of scope; upstairs the run has to fit within the floor depth, which sets a limit on distance. We survey the floor and stack before confirming, and where gravity won’t reach, a macerator can open up positions that otherwise couldn’t work.
Is it expensive to move the plumbing in a bathroom?
Moving the basin is cheap, the bath moderate, and the toilet is the one that adds real cost because of the soil re-route. That said, doing it during a full refit — when the room’s already stripped out — is far cheaper than as a standalone job later. Keeping the plumbing where it is is the biggest saving on any bathroom, so we’ll always show you the cost of a move clearly so you can judge whether it’s worth it.
Do I need a macerator to move my toilet?
Only if a normal gravity soil run genuinely can’t reach the position you want — a loo far from the stack, under the stairs, or in a loft en-suite. Where a gravity connection is achievable, it’s more reliable and maintenance-free, so that’s what we’d recommend. A macerator is a great solution for the positions gravity can’t serve, but it’s not something to fit for the sake of it.
Proud of every bathroom we fit
Get the layout you actually want
Whether it’s shifting a basin or reworking the whole room, we’ll survey the floor, the stack and the falls, tell you honestly what’s straightforward and what isn’t, and price the layout you want on one clear quote. Tell us how you’d like your bathroom to work.