Bathroom Plumbing: A Homeowner's Guide

Bathroom plumbing is the network of pipes, traps and fittings that brings clean water to your taps, shower and WC and carries used water away. In an Indian home it has two parts: pressurised hot and cold supply lines, and gravity-fed drainage with a vent.

This guide explains each part in plain terms, so you can read a plumbing drawing, check a material list and supervise the work.

What Plumbing Does a Bathroom Need?

A bathroom needs cold and hot water supply lines, a soil line from the WC, waste lines from the basin and shower, traps at every drain point and a vent to the open air.

• Supply side: water reaches the bathroom under pressure, from an overhead tank, a pressure pump or the municipal line. A geyser (wall-mounted water heater) feeds the hot line.
• Drainage side: used water flows downhill by gravity, through traps, into a vertical soil stack or an outside gully trap.
• Soil pipe vs waste pipe: the soil pipe carries WC discharge. The waste pipe carries water from the basin, shower and floor trap.
• Vent pipe: an open pipe that lets air into the drains, so water flows smoothly and sewer gas escapes above the roof.

Many Bengaluru homes store water in an underground sump and pump it to a terrace tank. That tank height decides your shower pressure, which matters when you pick fittings.

Which Pipe Is Best for Bathroom Plumbing?

CPVC is the default pipe for hot and cold bathroom supply in India, and SWR pipe is the default for drainage. PPR is a good alternative for supply, and plain UPVC suits cold water only.

CPVC comes in pressure classes called SDR (the ratio of outside diameter to wall thickness). A lower SDR means a thicker wall: SDR 11 suits pumped or boosted supply, and SDR 13.5 often suits a gravity tank system.

Concealed pipes look neater but are hard to reach if they leak. Exposed pipes are cheaper and easy to repair, which suits rented homes and utility bathrooms.

How Is a Bathroom Plumbing Layout Planned?

A bathroom plumbing layout starts from the soil stack or shaft position, because the WC must sit close to it. The basin and shower then go along the same "wet wall" to keep pipe runs short.

• Locate the plumbing shaft (duct) or the outside stack and the main drain exit
• Fix the WC first, as near the stack as the room allows
• Group the basin, shower and WC on one or two adjacent walls
• Decide the geyser position close to the shower to cut hot-water wait
• Mark the floor trap at the lowest point, away from the door
• Choose Indian (squat) WC or EWC (European water closet, the Western commode) now, since the two need different drain positions

A basic layout drawing shows each supply point (hot and cold in different colours), drain points, the floor trap, the stack and the floor slope arrows. Ask your plumber for one before work starts.

What Are the Standard Rough-In Heights for Bathroom Fittings?

Rough-in is the stage where pipes are laid inside walls and floors, with outlets left at set heights before tiling. Typical Indian heights put the basin inlets about 550 mm and the shower mixer about 1,050 mm above the finished floor.

For the WC, an S-trap EWC (outlet through the floor) is sold to suit set wall-to-outlet distances, commonly 220 mm or 300 mm. A P-trap EWC (outlet into the wall) needs its drain at the model's outlet height, often about 180–230 mm.

How Is Plumbing Done in a Bathroom, Step by Step?

Plumbing in a bathroom follows a fixed order: drainage first, supply second, tests before waterproofing, and fixtures last. Use this sequence to supervise an experienced plumber.

Use the test pressure and duration that the pipe maker or your engineer specifies, since they vary by pipe type and class. Our bathroom waterproofing guide covers the membrane and flood-test step.

• Supply lines hold test pressure with no drop on the gauge
• Every drain point flows freely and no joint weeps
• Pipe sleeves through the slab are sealed into the waterproofing
• Concealed valves and the diverter can be reached later
• Photos of every wall are taken, with tape measurements, before tiling

How Do the Basin, WC and Shower Connect?

Each fixture has a supply connection, a trap and a waste or soil connection. Most leaks start at these joints, so they deserve a check after installation.

Wash basin

An angle valve (angle cock) on each supply point feeds the tap through a flexible connection pipe. Below, a waste coupling and a bottle or P-trap carry water into the wall or floor drain.

WC and health faucet

An exposed cistern or a concealed cistern behind the wall stores flush water. A flush valve is the alternative: it flushes direct from supply pressure, so it needs a larger pipe and strong pressure. The health faucet takes its own angle valve beside the pan.

Shower and bathtub

A diverter switches water between the overhead shower, hand shower and spout. Concealed diverters sit inside the wall, so fix the body at the right depth before tiling. See our guide to diverter valve types. A bathtub also needs a waste with an overflow.

• Dampness on the wall behind a basin: a loose flexible hose or angle valve
• Water around the WC base: a failed outlet seal or loose pan connector
• Damp patches below a shower wall: a leaking concealed diverter or poorly sealed sleeve
• Smell from the floor trap: a dry trap or a cracked trap body

Jaquar notes low-flow shower heads can work down to about 10 psi. Plan any pump before rough-in, because a pumped line suits the thicker SDR 11 CPVC.

Why Do Drain Slope, Traps and Vents Matter?

Drain slope, traps and vents decide whether a bathroom stays free of blockages and smell for decades. They sit under tiles, so mistakes here cost the most to fix.

• Slope: horizontal drains need a continuous fall. One Indian schedule suggests about 1 in 40 to 1 in 60 for a 100–110 mm soil line; the common US rule of ¼ inch per foot (about 1 in 48) falls inside that range. Too flat leaves standing water. Too steep lets water run ahead of solids.
• Bends: use long-radius bends or two 45° fittings instead of a sharp 90° elbow, which catches waste.
• Traps: every fixture needs one trap with a water seal of about 50 mm. Outside gully traps use a deeper 75 mm seal. Never fit two traps in series on one line.
• Vents: in multi-storey buildings the stack vents above the roof, so falling water does not suck traps dry.
• Access: leave a cleanout or inspection chamber where lines join, so a blockage can be rodded out without breaking tiles.

Confirm gradients and pipe sizes with your engineer against the National Building Code of India, Part 9 (Plumbing Services). In independent houses without a sewer line, the drains lead to a tank; see our septic tank design guide.

What Are the Main Bathroom Fittings Names?

Bathroom fittings fall into two groups: CP (chrome-plated) fittings you see, such as taps and showers, and sanitaryware, such as the WC and basin. Pipe fittings and valves hide behind them.

Put a main stop valve at the bathroom inlet so you can shut the room without shutting the house. Our explainer on the ball valve covers how a quarter-turn valve works.

For taps, a brass body with chrome plating is the common choice. Look for the ISI mark under IS 8931, the BIS standard for copper alloy taps and stop valves.

How Much Does Bathroom Plumbing Cost?

Bathroom plumbing in India costs about ₹22,000–₹42,000 per bathroom in 2026 for pipes, fittings and labour, excluding sanitaryware and CP fittings. Two published guides give overlapping ranges.

The quote rises with concealed piping, more points, a new soil stack, wall chasing and any tile breaking in a renovation. Ask for an itemised quote that lists material and labour separately, with the pipe brand, SDR class and number of points.

What Mistakes Cause Leaks and Rework?

The costliest bathroom mistakes are the ones buried under tiles: no test, the wrong pipe, poor slope and valves you cannot reach.

• Tiling before the supply pressure test and drain water test
• UPVC used on the geyser outlet or any hot line
• Flat or sagging drain runs, and sharp 90° elbows on the soil line
• Unsealed pipe sleeves through the waterproofing layer
• Concealed valves with no access plate or removable trim
• Fixtures bought after the rough-in was fixed

Your next step: finalise the fixtures, ask the plumber for a layout drawing with heights, and get an itemised quote before any wall is chased.