In all of these cases, water has to pass through two separate traps, called a double trap. But don't confuse this with two separate traps, which is fine. Of course, those corrugated things in the photo above aren't proper, but the configuration is correct. Plumbing codes expressly prohibit the use of double traps.
Anytime your drain goes up and down more than once, you have a double trap UNLESS you place an air vent between the two traps that vents ABOVE the drain inlet. The double trap causes drainage issues because air becomes trapped between the two traps, and air is lighter than water.
While installing two traps in series might appear to be a good safety measure, this practice is not recommended because it can lead to trap blockage and waterlogging of all equipment trying to drain into it, similar to when a trap is completely blocked.
No fixture shall be double trapped. Exceptions to the separate trapping requirements are as follows: (1) Fixtures having integral traps. (2) A combination plumbing fixture may be installed on one trap provided one compartment is not more than 6 in.
Yes. A vent is required so that the sewer gas can escape the house safely. The vent should always be located after the P-trap, not before it.
Yes, the toilet and sink can share the same vent, as can the shower. It's common to have one main vent pipe for multiple fixtures, although you might need a larger pipe. You should check with local building and plumbing codes to confirm you'll have adequate piping for your home.
As we previously mentioned, it is a law in the United States that every shower has a P-trap. In addition to this rule, P-traps must be no more than 5 feet away from the shower drain. Ideally, it should be as close to your shower inlet as possible.
When it comes to installing drains, size matters. The recommended pipe size for a shower drain is 2 inches, whereas most tubs use 1.5-inch pipes. Why the difference? Shower pans are shallower than tubs, so there's a higher risk for overflow.
Section P-505 Bath Traps
The minimum size trap shall be 1-1/2 inches inside nominal diameter and shall have a water seal of not less than 2 inches and not more than 4 inches. Traps for bath tubs shall be made of cast brass, cast iron, DWV copper, galvanized durham piping, ABS, or PVC.
Plumbing codes expressly prohibit the use of double traps.
P-traps are known for their reliability and efficiency in maintaining a water seal, which helps to prevent sewer gases from entering buildings. Additionally, P-traps are less prone to syphoning and drainage issues compared to S-traps, making them a preferred choice for both residential and commercial plumbing systems.
Traps are also inhumane, exposing animals to psychological trauma, dehydration, excruciating pain, injury, self-amputation, depredation, and a slow death. The public generally abhors trapping, yet many states persist not only in permitting it, but allowing it to happen largely unregulated.
Disadvantages of P-Traps
One common issue is that the water seal can be protected if properly maintained or if there are blockages in the drainpipe. This can lead to the escape of sewer gases and unpleasant odors. The trap is regularly inspected and cleaned to ensure its proper functioning.
When pushing the cable through the P-trap, the U-shaped pipe section under the sink, you may encounter some friction and resistance. If this happens, push on the cable while cranking the drain snake slowly. A couple of turns will help the cable maneuver through the bends in the pipe.
The low profile p-trap is one of the freestanding tub fittings, the 1-1/2" p-trap ends with a nut that connects to another 1-1/2" Threaded drain for bathtubs such as RV tubs, etc.
The standard drain line size for a toilet is 3 inches in diameter, which is recommended to ensure proper drainage and prevent clogging. It's important to check local building codes for specific requirements, as they can vary by region. Storables provides a comprehensive guide on standard sizes and regulations.
A 1 1/2 in. drain can easily accommodate 4.9 gpm for cast iron and 8.3 gpm for PVC. While the flush typically occurs within 12 seconds, the flow levels out quickly in the drain.
The “S” trap is prohibited under the Uniform Plumbing Code throughout the United States. This is because the “S” trap will siphon or suck water out from the trap which will end up releasing methane (sewer) gases into the home. So, it is a code violation and if you are doing remodeling, you will have to replace it.
Waterless traps
Wavin Osma's HepvO waterless trap provides a hygienic alternative to the traditional trap because it cannot dry out. Its self-sealing membrane provides permanent, watertight protection.
When the trap is too deep, liquid may flow through it too fast, which can lead to siphoning of the trap seal and sludge buildup. The drain connection at the wall is too high on this sink, resulting in a 9-inch-deep trap seal — 5 inches deeper than is allowed by code.
Surprisingly, some building codes do not require bathroom fans. All municipalities have different requirements, but some do not draw a hard line on requiring exhaust fans. Bathroom ventilation is needed in those areas, but it can be from a window or fan—you choose.
All plumbing in your home must have vents to remove sewer gasses and regulate air pressure in pipes. When liquid goes down a pipe, air needs to follow it. Without the vent pipe, the liquid will attempt to draw air through the P-traps on your tub or sink. This will create a gurgling sound.
Toilet Vent Pipe Size? It's typically recommended that you go with a 2" PVC pipe for the vent. This is according to the uniform plumbing code (UPC).