Laundry Sink Without a Trap

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MicEd69

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I've seen diagrams where by code a laundry sink can be installed without a trap if it is drained into a 2" washing machine standpipe that has a trap, provided the sink is not more than 30" away. Why is the limit 30"? A 1 1/2-inch sink drain with a trap can be installed 42" from a main stack. And the only reason for that 42" dimension is so there is not a possibility of the drain line flooding and pulling the trap dry. I understand the reasoning for not allowing a trapped drain line to flow into another trapped drain line. But if a laundry sink without a trap is drained into a washing machine standpipe that has a trap, there is no risk of sewer gases entering the house even if the laundry sink is more than 30" away, or more than 42" away, or even more than 60" away. The 2" washing machine trap cannot become dry with this laundry sink drainage arrangement. I know codes are in place to provide safe installations, but the 30" limit on a laundry sink draining into a washing machine standpipe doesn't seem reasonable. What am I missing?
 
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So you don’t agree with the plumbing code. What am I missing ? 😀
 
Everything in the code has a reason for being in the code. My question is to try to understand the reasoning for this requirement being in the code. The height of the washing machine standpipe, the venting requirements of plumbing fixtures, the use of sanitary tees, etc. all make sense to me. This one doesn't. Thanks for the response, but it did nothing to provide an answer to the question I posed.

And I never said I didn't agree with the plumbing code, just questioning this item.
 
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Stuff grows in drain lines. The longer the drain is from the trap the more pipe there is to grow bacteria.

so there ya go, it’s for sanitary reasons.
 
Again, thanks for the feedback. I can see where that can be a plausible reason, but it still seems questionable to me. One can have a triple compartment sink with each compartment draining into a common line with a single trap at one end of the triple compartment sink, provided each compartment drain is no more than 30" from each other. That would mean that the common line from the farthest compartment to the trap would be a minimum of 60". So, what's the difference between that layout and a layout with a laundry sink 60" from the washing machine standpipe trap? Is the 60" laundry sink drain line going to grow more bacteria than the 60" drain line in the triple compartment sink? Just trying to understand the reasoning for the 30" maximum laundry sink drain line to the washing machine standpipe code requirement.
 
Do you think the code is consistent?

Plumbing codes are not consistent. Plumbing code contains theory.....

What’s the reasoning behind the 30” from the standpipe ? Sanitary considerations are the reason.

It’s just that simple, the code is not consistent and it can vary from location to location.

Expected use is also a factor. A three compartment sink in “ theory “ would be used more.
 
Any code, (plumbing, building, ASME pressure vessel, etc.) can have inconsistencies, but those inconsistencies are addressed and codes revised to correct them. And NO code has anything included based on "theory". They are in place based on issues that have occurred, or that can occur within reason, in real life. I would expect there are thousands of triple sinks in church kitchens across the country that are used only a few times a year. But a laundry sink in a normal home is probably used several times a month, if not multiple times a week.

So, assuming you are correct that the issue for the 30" maximum from sink to washing machine standpipe is solely for sanitary reasons, while it not per the plumbing code, having it 60" away from the standpipe would not be any more of a concern than an infrequently used triple compartment sink. And as the laundry sink will be used for hand washing clothes and even soaking items in bleach, there seems to be a very slim chance of pipe bacteria growth in the extra 30" of drain pipe causing a problem.

Thanks for your input.
 
Sorry but the code has plumbing theory included by the code writers.

It’s “ their theory “ ......that’s why there are different model codes.

The jurisdictions that adopt these codes then can delete or add to the code as they see fit.

You don’t have to agree with me but that’s how the cookie crumbles. 🤣
 
Codes are based on history, engineering principles, facts, and sound reasoning. But I guess if one defines the word "theory" to describe something that some people believe can reasonably be expected to occur, rather than an abstract thought or idea, then saying a code has some theoretical items in it is correct. That's just not my definition of the word "theory".

Again, thanks for your input.
 
MicEd69 said:
Codes are based on history, engineering principles, facts, and sound reasoning. But I guess if one defines the word "theory" to describe something that some people believe can reasonably be expected to occur, rather than an abstract thought or idea, then saying a code has some theoretical items in it is correct. That's just not my definition of the word "theory".

Again, thanks for your input.
Click to expand...

So you don’t agree with me and you don’t agree with the code..

How long have you been a plumber ?

I have 35 yrs in so far, with over 20 in business so I think I’m qualified to give an expert opinion. It’s good enough for me to testify in courts of law. 🤡✌️

Here is a school that teaches plumbing code and theory. I didn’t just make it up.......it’s a well known fact that plumbing code is based off plumbing theory.

https://smith-adult-community-education.myshopify.com/products/plumbing-code-and-theory
Have a good day.
 
Theory is often used to develop how to size water pipes, drain piping and vents.

It’s based off expected use and that is based on Queuing theory. It’s used to determine the required facilities of a public restroom.

So a lot of the pipe sizes and subsequent restrictions are ultimately determined by theory.

When these theories do not hold true you get codes changes.......eventually.

Some of the plumbing code is based off principles........but not all of it. It’s not all fact......
 
Gee Twowaxhack, sorry I upset you so much. Again, where did I say I didn't agree with the plumbing code? My questions are simply trying to understand the reasoning behind one code issue.

I am not a plumber, but a Registered Professional Engineer. I attended the University of Missouri at Rolla, graduating with BS in Mechanical Engineering. I have over 45 years of experience in major refinery and chemical plant projects. I have worked for only two companies in my career, both Fortune 500 companies and leaders in their industries. So, I admit that my experience is largely limited to industrial codes; ASME, Structural, NEC/NFPA, etc., which are significantly more involved than the International Plumbing Code. And those codes, Twowaxhac, have NO theory as a basis for their requirements. They are solely based on empirical data, engineering principles, mathematical calculations, basic facts. And I too have had the occasion to testify in court on engineering construction issues.

And also again, the way one interprets the word "theory" may be our only disagreement. Water pipes, drainpipes, and vents are sized based on a set of parameters and developed by calculations. If you choose to call that "set of parameters" a "theory", then I can agree with your statement that the plumbing code as some "theory" behind it. But there are NO instances in the plumbing code that are solely based on theory. A calculation has been made based on a set of parameters that comes from a reasonable scenario of operation. And while Queuing theory is used to determine the number of units in a public restroom based on the building's occupancy, the supply, drain, and vent sizing is based on calculations of a set of operating parameters.

So maybe we aren't that far apart. Please just calm down and let's be friends.
 
In your first post on this forum you wanted an explanation as to why the limitation of 30” from a standpipe.

I answered that question and as to why.

i think I’m calm..,,.,🤣🤷

Im posting for the benefit of others that may be reading.

have a great day
 
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That's just it Twowaxhack, you did not answer my question in response to my first post on this forum. You simply said in a rather sarcastic way, "So you don’t agree with the plumbing code. What am I missing?"

I had to re-ask my question before you stated any opinion. That then led to our discussion on inconsistencies in the code which somewhat contradicted your answer of why there is a 30" maximum dimension for the laundry sink to washing machine standpipe. And then our discussion further escalated as to the basis of the code; theory versus mathematical calculations based on a set of parameters that comes from a reasonable scenario of operation.

If your initial response had been an actual answer to my question, this thread would have been much shorter. :)
 
MicEd69 said:
That's just it Twowaxhack, you did not answer my question in response to my first post on this forum. You simply said in a rather sarcastic way, "So you don’t agree with the plumbing code. What am I missing?"

I had to re-ask my question before you stated any opinion. That then led to our discussion on inconsistencies in the code which somewhat contradicted your answer of why there is a 30" maximum dimension for the laundry sink to washing machine standpipe. And then our discussion further escalated as to the basis of the code; theory versus mathematical calculations based on a set of parameters that comes from a reasonable scenario of operation.

If your initial response had been an actual answer to my question, this thread would have been much shorter. :)
Click to expand...

You received all the answers to your questions within 6 posts. You just don’t agree with the answer you received. This is post #15 and my answer is the same and will stay the same.

Nothing was contradicted. There are set distances for various fixtures based off theory of probable use.

Its all based on theory derived from principles. 🤓


Do you have anymore plumbing questions I could help you with ?
 
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The point is Twowaxhack, I had to ask my question twice before receiving your input. Your initial response was dripping with attitude and stated a falsehood that I didn't agree with the code. That is not what I said or asked and isn't even implied in my question.

And no, I don't have any additional plumbing questions that you can help me with. I really don't think I can use any input from a person who has an attitude like yours.

And as I responded in another thread, you have convinced me that plumbing code is significantly based on theory. My hang-up was on the word "theory" versus "proven science".

So, I now agree that some of the IPC is based on empirical science, physics, and mathematical calculations, while some other parts are only based on plumbing theories.

Please just end this!
 
MicEd69 said:
The point is Twowaxhack, I had to ask my question twice before receiving your input. Your initial response was dripping with attitude and stated a falsehood that I didn't agree with the code. That is not what I said or asked and isn't even implied in my question.

And no, I don't have any additional plumbing questions that you can help me with. I really don't think I can use any input from a person who has an attitude like yours.

And as I responded in another thread, you have convinced me that plumbing code is significantly based on theory. My hang-up was on the word "theory" versus "proven science".

So, I now agree that some of the IPC is based on empirical science, physics, and mathematical calculations, while some other parts are only based on plumbing theories.

Please just end this!
Click to expand...
You can't hear tone in a written word. Only the interpretation of tone. It leads to misunderstandings.
 
Yes, I agree. But when one asks a question and rather than receiving an answer you get, "So you don’t agree with the plumbing code. What am I missing ? 😀", you don't need to hear anything to understand the tone in which those words came. Nowhere in the question did I say I disagreed with the code, I just wanted to understand the requirement. To get an actual answer, I had to ask a second time. And the answer was followed by, "so there ya go, it’s for sanitary reasons." Another curt response that demonstrated "attitude".

Being accused of not agreeing with the code, and having to ask my question a second time, shows the lack of help and attitude from the responder.
 
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