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A tub is heavier and more awkward than it looks. It has to come in through doorways, sit level on a floor that can carry it when full, and connect to a drain that is usually hidden beneath it. Reaching that drain often means an access panel, the ceiling below or part of the wall surround, which is why the plumbing is best planned before the tub is chosen.
Bathtub types and their plumbing: alcove, drop-in, freestanding, soaker and jetted
- Alcove: the most common tub, set between three walls with a finished front; the drain and overflow sit at the faucet end, and the wall surround usually doubles as a shower.
- Drop-in: a shell set into a built deck or platform, which hides the plumbing but needs an access panel in the deck to reach the drain and valve.
- Freestanding: a tub standing on its own, often away from the walls, fed by a floor-mounted filler or a wall spout, with a drain that has to come up through the floor exactly where the tub's outlet lands.
- Soaker: a deeper tub for full immersion; it holds more water, so the water heater has to be able to fill it and the floor has to carry the extra weight.
- Jetted and air tubs: a pump or blower drives the jets, so they need an electrical connection by an electrician and an access panel for servicing.
Bathtub drain-waste-overflow assemblies: how the tub drain works and where it leaks
Under every tub is a drain-waste-overflow assembly. The drain shoe connects to the outlet at the bottom of the tub, the overflow elbow connects to the opening below the rim, and the two meet in a tee that runs down to a trap under the floor. The stopper, whether lift-and-turn, toe-touch, push-button or trip lever, is part of the same assembly.
Most tub drain problems start here: a dried-out gasket at the drain or overflow, a slip joint that has worked loose, or a trip-lever linkage matted with hair. Because the assembly sits behind the tub, a leak tends to show up as a stain on the ceiling below or damp flooring beside the tub rather than a visible drip. When a tub is replaced, fitting a new assembly is part of the job; reusing an old one saves little and risks a leak you can't easily reach.
Installing a freestanding tub: floor drain location, supply lines and filler
With a freestanding tub, the drain has to rise through the floor at exactly the spot where the tub's outlet will sit, so the tub is usually bought and its drain position confirmed before the floor is opened. The trap goes between the joists below, or into a cut in the slab on a concrete floor, and the waste and overflow on these tubs is often a finished piece that stays in view.
A floor-mounted filler needs supply lines brought up through the floor and a solid mounting to the framing, with its valve reachable for service; a wall-mounted spout needs the tub close enough for the water to land inside it. Leave room to clean around the tub, and decide how the drain will be reached later, from the ceiling below or through an access panel. New drain and supply routes are plumbing alterations, so they belong with a licensed plumber and may need a permit.
Heavy tubs and floor structure: when to bring in a structural engineer
A full tub concentrates the weight of the tub, the water and the bather on a small patch of floor. Cast iron and stone tubs, deep soakers and large freestanding models weigh far more than a standard acrylic alcove tub, and older houses may have joists that earlier renovations notched or drilled. A floor that sagged, bounced or cracked tile around the old tub is a warning sign.
Before ordering a heavy tub, get the manufacturer's filled weight and share it with your contractor. If there is any doubt about the joists, especially for a tub placed mid-span or on an upper floor, a structural engineer can assess the framing and specify reinforcement, which is far easier to add while the floor is open.
Tub-to-shower conversion: what changes in the plumbing
Swapping a tub for a shower changes more than the enclosure. The tub drain sits at one end, while a shower base or tiled pan usually needs its drain in a different spot, so the trap is often relocated and the drain fitting changed to suit the new base. The valve usually stays in the same wall, but the spout and diverter come out and the showerhead may move higher.
It's also the natural moment to replace an old two-handle or non-balancing valve with a pressure-balancing or thermostatic one. The waterproofing, tile and glass that follow are part of a bathroom renovation, and families with young children may want to keep one tub somewhere in the house.
Scald prevention at the tub: mixing valves and checking bath water
Tubs are where young children are most exposed to hot water, since they sit in it and may reach for the tap. The Government of Canada recommends automatic mixing valves on tubs, showers and faucets, or an anti-scald mixing valve at the water heater, set to deliver 49°C (120°F), and advises starting and ending with cold water when running a bath and testing it with your elbow before a child gets in.
A tub valve with pressure balancing or thermostatic control guards against sudden swings, and its limit stop should be set at installation. If the bath seems hotter than it used to, have the mixing valve or limit stop checked, particularly after the water heater has been replaced or adjusted.
Adapt the tub or replace it: grab bars, walk-in tubs and accessible bathing
When stepping over a tub wall becomes difficult, the answer ranges from small changes to a new fixture. CMHC's list of low- and no-cost accessibility modifications includes a safety mat and grab bars in the tub, and a water alarm that warns when a tub or sink is overflowing, useful for anyone who might forget a running bath.
- Grab bars: fastened into solid blocking or with anchors made for the purpose, never a towel bar, and placed where a person actually shifts their weight getting in and out.
- Handheld shower on a slide bar: lets someone wash while seated, and can often be added at the existing valve with a diverter.
- Walk-in tub: a tub with a watertight door and a built-in seat; the bather gets in before it fills and waits for it to drain, so hot-water capacity and drain speed matter, and many models need electrical work.
- Low-threshold shower: replacing the tub with a curbless or low-curb shower is often simpler to use than a walk-in tub, and is planned as part of a bathroom renovation.
Bathtub Plumbing: frequently asked questions
Why is water leaking from under my bathtub?
The usual suspects are the drain-waste-overflow gaskets, a loose drain or overflow plate, or the spout and valve connections in the wall. Failed caulk where the tub meets the wall or floor can also let shower water run underneath. A plumber can fill the tub with the stopper closed, then drain it, to see which part leaks.
Can I put a freestanding tub where my alcove tub was?
Often, but the drain usually has to move, since a freestanding tub's outlet sits in a different place, and the filler needs a new supply route. The walls and floor the old tub covered also need finishing. Check the new tub's filled weight against the floor structure before you commit.
Do jetted tubs need special plumbing?
The water side is much like any tub, but the pump or blower needs its own electrical connection by an electrician, and the tub needs an access panel so the pump can be serviced. The jet lines also need regular cleaning so water doesn't sit in them.
Is a walk-in tub a good choice for aging in place?
It can be, for someone who wants to soak but can't step over a tub wall. The trade-offs are sitting inside while it fills and drains, a large demand for hot water, and more plumbing and electrical work than a standard tub. For many people a low-threshold shower with a seat and grab bars is simpler; an occupational therapist can help weigh the options.
Should the tub drain be replaced along with the tub?
In most cases, yes. An old drain-waste-overflow may be brittle, corroded or a poor fit for the new tub's outlet, and replacing it while everything is open avoids having to reach it later through a ceiling or access panel.
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Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides