What size drain pipe do I need for a shower?
A 2-inch pipe is the recommended size because showers have a low threshold for flooding, and a 2-inch pipe helps the water drain faster than does a 1 1/2-inch pipe. So, if you are converting from a tub and shower combination to a shower, you'll likely have to change the drain pipe size.
What is a Common Shower Waste Size? A common size for a shower waste is 120mm x 120mm. This size allows plenty of space for the standard 40mm (1½”) waste pipe and drain to be fitted, and provide efficient water removal.
When installing a shower in your bathtub, you can use a smaller drain pipe. Because the tub is designed to hold more water than shower trays, this reduces the chance of overflowing. One-and-a-half-inch pipes are sufficient to keep the water draining fast enough and not getting too backed up.
All national and local Building Codes for many decades have been very clear and should be well known to all professional tradespeople: bathtubs require a 1 ½” diameter drain line, while all showers require a 2″ diameter drain line. There are no exceptions to this code.
Polyvinyl chloride pipes (PVC) are commonly used as part of a sink, toilet, or shower drain line. Its plastic tubing is ideal for this kind of usage because it protects the water from rust and corrosion better than other types of pipes. This capability also makes PVC pipe incredibly durable.
The 1½-inch size is used to capture water that might flow out of a kitchen sink, a bathroom vanity or a tub. The two-inch pipe is commonly used to drain a shower stall or washing machine, and it may be used as a vertical stack for a kitchen sink. A three-inch pipe is what's used in homes to pipe toilets.
PVC Pipe Sizes in Australia
The external diameter of the pipe is 34mm. 20mm or ¾ inch pressure PVC pipe (in this case, class 12), has an internal diameter of 23mm with an external diameter of 27mm.
| Nominal Size | Outside Diameter | PN9 |
|---|---|---|
| DN | Dm min (mm) | ID (mm) |
| 32 | 42.1 | 38.5 |
| 40 | 48.1 | 44.1 |
| 50 | 60.2 | 55.2 |
Waste Pipes - 32mm for small hand basins, 40mm for sinks, showers, baths, washing machines and dishwashers, 50mm for commercial applications and connecting multiple waste pipes to a single flow.
A shower tub drain has a 2” drain connection, while a tub drain often has a 1 ½” drain connection. The drain connection for your tub is similar to the one for your sink, whereas the shower drain connection is slightly larger.
How much water can a 2 inch drain handle?
At 1/4" per foot slope, a 2" pipe can handle about 10 gallons per minute (there is some variance here depending upon whose chart you use).
For a 1 ½-inc pipe the vent should be 42 inches away at the most while a 2-inch pipe must have a maximum distance of 5 feet. For pipes that have a diameter of 3 inches the distance is 6 feet and for a 4-inch pipe the most it should be away from the vent is 10 feet.
The standard tub drain plug size is 1 ½” diameter. The drain size may be subject to local plumbing codes.
Drain Sizing
The average residential shower has a 2” waste line, which can usually handle water pouring into the shower area at a rate of 9 gallons per minute (GPM) without flooding.
In a stall shower, the plumbing code requires the floor to be sloped one quarter (1/4) of an inch per foot in order to carry the water effectively to the drain.
Point Drain or Linear Drain
Point drains are most common and are what we are used to seeing in showers. They are typically located in the middle of the shower floor, and the floor is sloped from all directions down to the drain.
A bath tub drain shall be a minimum of 2 (horizontal) or 1 ½ (vertical) drain pipe size, with a minimum 1 1/2 vent pipe size. A lavatory requires a 1 ¼ minimum drain and vent pipe size.
This weld-type drain fits either a two- or three-inch drainpipe. With a two-inch drainpipe, the body of the drain fits over the pipe; with a three-inch pipe, it fits inside. If your home has three-inch drainpipes, it pays to pick up a box of size-adaptable drains to have on hand.
The most common size pipe for modern drains is 1 1/2 inches in diameter, but there are also 2-inch and 3-inch pipes available. Some older sinks may have even smaller pipes like 1 1/4-inch in diameter but these are not as common. If you have a standard kitchen sink drain, then a 1 1/2-inch pipe is typically sufficient.
If you purchased your PVC pipe from a hardware store, you can use the markings on the side of the pipe to tell you what size you have. It will normally indicate the size in decimal or fraction, close to where the manufacturer's name is, such as '1.25' (for 1-1/4") or "3/4" (for 3/4"...
How many toilets can be on a 4 inch drain?
| DIAMETER OF PIPE (inches) | MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS (dfu) | |
|---|---|---|
| 21/2 | 12 | 20 |
| 3 | 20 | 48 |
| 4 | 160 | 240 |
| 5 | 360 | 540 |
No more than four water closets or bathroom groups shall be installed on a 3" horizontal fixture branch. EXCEPTION: Where the water closets are rated 3.5 gallons or more per flush, no more than two water closets or bathroom groups shall be permitted.
Conclusion. In short, it is possible to connect the toilet drainage line and the shower drainage line, as long as they both have separate waste trap arms. However, do note that combining them may also lead to blockages, which can cause smells to come from certain drains.
| Toilet | Shower/Tub | |
|---|---|---|
| Discharge/Drain Hole from Back Wall | 12 1/2" | 14" |
| Discharge/Drain Hole (Vertical) | 0" | 0" |
| Fixture (Side to Side Buffer) | 15" to 18" min | 18" min |
| Fixture (Front Buffer) | 21" min | 18" min |
| Pipe Size | Maximum Flow Capacity |
|---|---|
| 3″ | 44.0 GPM |
| 4″ | 75.0 GPM |
| 6″ | 175.0 GPM |
Maximum length can be 26 m in vertical and unlimited in horizontal position. Similar 4 in (100 mm) pipe can carry total fixture units unto 256 DFU in vertical and 216 DFU in horizontal position. Maximum length can be 91 m in vertical and unlimited in horizontal position.
There are three common drain sizes for bathroom sinks, 1.25", 1.5" and 1 5/8 (1.625"). You need to select a drain that is the same size or SMALLER than the hole in your sink. For example, if you have a sink with a drain hole of 1.75", than any of the drains 1.25", 1.5", or 1.65" will work.
Oversized piping may contribute to health risks such as Legionella, sewage clogs, and odor fade. As time moves forward, plumbing fixtures and the use of plumbing systems changes, and new risks are discovered and studied.
According to the UPC, the distance between your trap and the vent should be no more than 6 feet. In other words, for the vent to work properly, it needs to feed into the drain line within 6 feet of the trapways that connect to it.
All change-of-direction fittings buried under a slab should never have any 90-degree fittings. If you need to change direction under concrete or other buried piping conditions say in a sewer line, you use two 45-degree fittings.
Does a shower drain have a pee trap?
Whether you have a standing shower or bathtub, it will always have a p-trap. The p-trap for showers is located underneath. Like the other fixtures, the shower drain p-trap prevents sewer odors from escaping your pipes.
Wastewater must not flow into the surface water drain. Unless your house is on a combined drains system, it needs separate drain connections to collect wastewater and rainwater. Homeowners and landlords are responsible for checking they have separate drain connections from their home.
According to regulations, all shower drains are required to have P-traps. This includes all fixtures connected to a building's main plumbing system. P-traps are curved pipes installed under showers and drains of all kinds.
But do you know the proper slope? The ideal slope of any drain line is ¼ inch per foot of pipe. In other words, for every foot the pipe travels horizontally, it should be dropping ¼ inch vertically.
The most important bit of obvious advice ever: soil and waste pipes need to be on a downhill gradient! The “fall” or “drop” should be between 1/40 (1cm down for every 40cm across) and 1/110. Too steep (1/10) then the water runs quicker than the solids so doesn't wash them away (ugh!).
