# Trap weird and crown weir

I am kind of new to all this so please bare with me =).

I am a little confused and could someone help explain this to me.

“Standpipes should extend at least 18 inches and no more than 42 inches above the trap weir.”

"The standpipe should be at least 30 inches high measured from the crown weir. "

The way I understood it was the trap weir is the part where the water leaves the trap, and the crown was the highest point of the trap.

Lets say a standpipe was 18" above the trap weir how could it possibly be 30 inches above the crown?

Thanks,

Dave

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You’re referencing three different dimensions. 18" is the minimum, 42" is the maximum and 30" is “optimal.”

The dimension is measured from the top of the weir.

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[quote=“rsmith24, post:3, topic:55346”]

David,

FYI… (ref: posted graphic)

Here in the land of basements, the trap is almost always located below the slab (95% of the time).

Always check with your local AHJ for the areas you operate in.

Jeff

PS… Welcome!](“http://www.nachi.org/forum/../gallery/”)

This one wasn’t in the slab. I called it out, only 8". Also I am thinking the tape is not allowed, correct?

Interesting. …

**HERE **in the land of basements, the trap is almost always located above the slab (99+% of the time).

This one wasn’t in the slab. I called it out as it was only 8" above the the top of the weir. Also I am thinking the tape is not allowed, correct?

They must have funny plumbing sytems in Mn. Here in the other land traps are throughout the the house , where needed ! ;):D:D

What did you say about the T being horizontal instead of vertical?

So, the question remains, where is the OP located? (That be you David)

Thanks guys I am located in Michigan but will be taking my NHIE exam soon to be able to do inspections in Indiana also.

I just want to make sure and know what I am talking about and to be honest I still think either I dont get it or what I read in the training materials here is not clear.

A response on here says that 30" is optimal but I cut and paste where it says 30" is minimal right out of the NACHI training here.

so still confused heh =)

Thanks,
Dave

file:///C:/Users/me/AppData/Local/Temp/moz-screenshot-11.png

A trap is designed to keep sewer gases and airborne bacteria from escaping the drainage system and entering the dwelling. Each plumbing fixture should be separately trapped by a water-seal trap, except as otherwise permitted by the plumbing standard. Fixtures such as water closets and urinals that have integral traps do not require an additional trap installed.
The vertical distance from the fixture outlet to the trap weir should not exceed 24 inches (610 mm). The vertical distance controls the drainage-flow velocity. If the trap has an excessively long vertical separation from the fixture, the velocity of the flow at the trap inlet can create siphoning.
The horizontal distance should not exceed 30 inches (610 mm), as measured from the center line of the fixture outlet to the center line of the inlet of the trap. The horizontal distance from a fixture to the trap limits the amount of bacterial growth and odor. It is desirable to locate the trap as close to the fixture as possible. A fixture should not be double-trapped.
Standpipes should be individually trapped. Standpipes, such as for a clothes washer, should have a minimum height above the trap of 18 inches (457 mm), and a maximum of 42 inches (1,066 mm). Access to all standpipes should be provided for cleaning and rodding.

First I want to say thank you Robert for the illustrations and effort. I feel like I am being a pain in the *** but I dont see where it explains this.

"The standpipe should be at least 30 inches high measured from the crown weir. "

Dave

Where are you getting that quote from? I copied and pasted from the Residential Plumbing Overview for Inspectors](http://www.nachi.org/forum/../plumbingcoursereleased2008.htm)

I must confess I did not notice the horizontal T. I see now where it could back up into the standpipe. I shall lookout for this from now on, thank you Robert for pointing this out.

Your welcome and when I see homeowner crap like this I also look at/for the cement used and in your attachment I don’t see any purple or orange.

I got it from “25 Standards Every Inspector Should Know”

“Standard #14: Standpipes”

The first line is "Standpipes should extend at least 18 inches and no more than 42 inches above the trap weir. The standpipe should be at least 30 inches high measured from the crown weir. "

Dave

Hi Dave

I am confused by the contradiction just like you are.
Maybe there is an error in the page of that particular page of “25 Standards Every Inspector Should Know” and the answer is in Robert Smoth’s quote “The horizontal distance should not exceed 30 inches (610 mm), as measured from the center line of the fixture outlet to the center line of the inlet of the trap. The horizontal distance from a fixture to the trap limits the amount of bacterial growth and odor. It is desirable to locate the trap as close to the fixture as possible. A fixture should not be double-trapped.”

So the 30" really refers to another part in the system.

Gabe

I found the following
“The horizontal distance from the fixture outlet to the trap weir should not be greater than 30 inches, measured from the centerline of the fixture outlet to the centerline of the inlet of the trap”
http://education.nachi.org/show.php?..6&course_id=54

Obviusly the contradiction mentioned earlier, is an error.

Gabe

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