How To Look At A House
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What plumbing traps are illegal by code?
Tuesday, April 14, 2020
Here are six types of plumbing traps that are not approved by the International Residential Code. Here’s the citation:
1) Building Trap - This is a kind of “whole house trap” that is on the final line out to the sewer. It dates back to the time before individual traps were required for each plumbing fixture, and has been prohibited by the building code for many years. See our blog post What is a building trap? for more details.
2) Bell Trap - This one is essentially a water reservoir cup with a bell shape over it that dips into the cup to form a seal. It is not self-scouring, the seal depth is very shallow, and it is a sluggish drain that clogs easily. Earlier versions of this trap, like the one shown at right, had a curved top seal that more closely resembled a bell.
3) Bottle Trap - These occasionally are included in the box with “designer” sinks when the trap will be visible under the sink. Although not specifically named above, they fall into category #2 of “traps with interior partitions” and are also not self-scouring as required. May be allowed to be installed if corrosion-resistant material under special conditions by local jurisdiction.
4) Drum Trap - Not self-scouring. Often used as a sediment trap to separate out small solids before they enter the drainage system. May be approved to be installed under special conditions by local jurisdiction, such as for a dental clinic, if corrosion resistant material. To learn more, see our blog post What is a drum trap at a plumbing drain?
5) S-Trap - It’s called an S trap because the shape is a sideways “S.” The trap seal tends to get sucked out when draining because it is unvented. Was once acceptable, but has not been approved for many years. See our blog post What is an S-Trap? for more details.
6) Trap with moving parts - We have not seen one of these mechanical anti-suction devices in a drain in a long time. No picture for this one.
What’s not illegal? A vented P-trap is always a good choice. Learn more at What is a P-trap?
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