Where does the P-trap go?

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Jadnashua

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The thing that makes a low-flow toilet work is the huge plug of water that gets dumped quickly. While it may not be as long in duration as an old water hog, when it does flush, there's momentarily a LOT of water.
 

Terry

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Today's toilets will siphon a tub. More water is released at once now.
Like Jim mentions, the olds bowls acted very slowly. That has all changed.

If you wet vent a lav over a toilet, then it's 2" all the way through the roof.
If you have a tub, it will be vented after or downstream of it's p-trap
 
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Dlarrivee

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mtcummins, I'm not sure that you have a clear understanding of venting.

Did you look at a different picture than the rest of us? I noticed the toilet not being the last thing before the pit, right away, that's why I never mentioned wet venting. I'm pretty sure any properly wet vented bathroom group will always have the toilet furthest down stream.
 

blackm3sedan

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I'm tending to agree with mtcummins. As the slug of water from the toilet travels down the center pipe, the vacuum will be broken as it passes where the vented vanity is tee'd into the main line. When the slug of water passes the tub tee, there will be no more vacuum behind the slug.

I do have a borescope, but it's only 3 ft long and I can only see to just before the trap or elbow. From the other pictures I've taken, it appears that the trap or elbow is beneath the concrete footer, so I'll be doing some digging this weekend, although it'll just be in dirt.
 

Dlarrivee

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Unfortunate that you disagree with the plumbers here and agree with the new guy who doesn't believe in code...
 

blackm3sedan

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Unfortunate that you disagree with the plumbers here and agree with the new guy who doesn't believe in code...

I agree with him based on my knowledge as a mechanical engineer with a basic understanding of fluid dynamics.

Please explain to me how my description or my logic is flawed.
 

blackm3sedan

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I corrected myself in a following post. The overflow does provide a vent as the water is draining through the bottom of the tub. I agree that it does nothing to vent the vacuum created in the line downstream of the p-trap.

So am I wrong? The way I think of it is that the toilet flush acts as a large piston traveling down the pipe. Wouldn't the vent in the lavatory provide relief to the vacuum left behind from a toilet flush? If there's no vacuum, how can the water in the p-trap be siphoned out?

I'm here for help. Please explain to me why I'm wrong so that I can learn something new.
 
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Dlarrivee

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The problem comes when somebody flushes the toilet while the faucet is also running at the sink (or the sink was full and is draining)...

99/100 it would be fine, but I'd prefer it to be impossible to siphon the trap, not a 1/100 odds that it will.
 

MTcummins

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Please note that I have continuously deferred to the pro plumbers for legality of setup, etc. I was merely positing the question of whether it would in fact siphon or not. I don't know exactly how a toilet flush goes through a 3" line, but IF, and only if, it didn't have enough water passing at once to completely cover the 2" inlet from the tub and the 2" wet vent from the lav, it probably wouldn't siphon in this setup. If that is not the case, then the vent will not help at all.

As I've said before, I personally don't believe in wet venting anything, so I never do this setup... I always vent every trap individually in my installations. I don't know a lot about proper wet venting b/c I don't ever do it or allow it to be done by plumbers on my jobs. I'm not sure, my county also might not allow any wet venting other than a toilet venting off a stack (seem to recall something about that from one of my plumbers), so its just not something I deal with.

In thinking through what the plumbers have said, and how blazingly fast today's toilets drain out 1.6 gallons compared to the slow draining of the old guzzlers... that would pretty much have to fill the 3" line high enough to siphon the trap. So, I'm in agreement with the pros that this setup will become unsafe if you don't leave the water running in the tub at all times to refill the trap :p

For the record, I fully believe in the concept of code. I think that it should be followed any time it is reasonably feasible to do so. I don't necessarily believe in the current system of enforcement, I've seen too much corruption in it, and there are too many problems with it for me to say that I think its a good system these days. However, I do advocate doing things to code whenever possible. If a situation like this comes up where getting it to code is quite difficult, and there is a practical solution that is functional and safe, I'm ok with going slightly outside the code. Agree with me or not, I'm not here to convince anyone, but I deal with stupid code crap every day that makes no sense, and have accepted that sometimes you're better off doing it the right way in the circumstance than blindly following the code. That said, 99.9% of my work is up to code, there are just a few odd circumstances where it makes sense to do a good solution that might be outside the general bounds of code. Given what's been discussed here, I don't see any good way to do this properly w/o digging it out and doing it up to code if there is indeed a trap down there.

Was this rough-in inspected? Do you have documentation? I believe you have a claim against the inspector, as well as the plumber who pulled the permit for the inspection, if it was passed in this form, but maybe the more experienced plumbers can chime in on that as well. If it wasn't inspected, you're on your own for the repairs.
 

Dlarrivee

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In this case the code provides good instruction on how to install this system and have it work under ALLL CIRCUMSTANCES.
 

MTcummins

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In this case the code provides good instruction on how to install this system and have it work under ALLL CIRCUMSTANCES.

At this point I agree, in this circumstance. I think it has been determined that there is no proper and safe way to make this work (if there's a trap down there) w/o tearing it out and doing it to proper code requirements. That is a bold statement though, to assume there isn't a similar circumstance that you could do something outside of code boundaries that would function properly... But, that's moot at this point, as I conceded in my previous post that I think the ONLY solution in this circumstance is to dig it out and do it to code.

However, if for example this had been roughed with everything to code except the trap arm on the tub was 62" long, at which point a proper vent was installed, would you seriously tell this guy to tear out all his concrete to move the vent 2" closer to the trap? That was my point, not that it should be set up wrong in the first place (or anything of the sort), but sometimes a situation calls for doing (or leaving) something safe, but slightly outside of code parameters. This is not one of those situations, it seems.
 

Dlarrivee

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If it was vented it wouldn't be a problem. I'm not sure what you want me to say? Moving a vent over 2" is not the same as exempting it from your design...
 

Cacher_Chick

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The tub rough in has no vent. There is an existing stack, which could be continued upwards. As an alternative, a wye could be cut into the horizontal drain outside, and the vent could be run up a chase in or on the outside wall. Either way, if a vent is not added, it does not meet any plumbing code, which is the MINIMUM requirement for a safe and proper installation.
Would you have your mother driving a car with only one lug nut holding on the wheels? It makes no sense to hope something "might work" when there are minimum standards already in place.

This type of work requires a permit and inspection to ensure that these minimum requirements are met. It is not in anyone's best interest to make recommendations or suggestions that circumvent a safe and legal installation.
 

MTcummins

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And what do you want me to say that I haven't said already... I AGREE WITH YOU... this needs to be torn out and redone to code... do I have to spell it out more clearly?

You made a statement that code is to be followed in all circumstances. This example was a completely different situation where I would say that its not critical to do so. That has no bearing on this instance, only an example of how code-to-the-letter is not always the answer in every circumstance.

Once again, I'm agreeing with you and the others that this cannot be worked safely without tearing it apart (assuming a trap is down there). Once you've done that, there is absolutely no reason to not bring it up to code, and I fully advocate doing it to proper code.
 

blackm3sedan

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The problem comes when somebody flushes the toilet while the faucet is also running at the sink (or the sink was full and is draining)...

99/100 it would be fine, but I'd prefer it to be impossible to siphon the trap, not a 1/100 odds that it will.

You're correct. My assumption was that only one person was using the bathroom at a time.

However, I think there are some flaws in your assumption. You're assuming that the water from the sink is filling the entire 2" drain line. Since the drain from the sink is only 1.25" diameter, I don't think this is possible without adding pressure to the sink drain to get the equivalent flow. It's plausible that there is enough room in the 2" drain line for the water and enough air to fill the vacuum.

Even without assuming there's still a direct path to atmosphere, the water from the sink is still filling the void behind the slug of water from the toilet, thus eliminating the vacuum and preventing the siphon. When the water from the sink is finished draining, it will be vented to atmosphere, thus eliminating the vacuum also.

With the exception of possibly not meeting the 24" maximum vertical separation between the trap and the drain (assuming there is a trap at the bottom of the riser), I haven't seen any evidence of it not meeting. In my interpretation, I think it meets the code for a wet vent, although I am obviously no expert. It was installed by a licensed plumber and it has been inspected by the county plumbing inspector with signatures. Neither of those statements means that system was installed correctly.

I've attached links to the Florida Building Code section on plumbing vents and plumbing traps, if someone wants to spend more time than I would ever ask to to help me interpret the code.

https://docs.google.com/open?id=0B95LjMhGv-qmMjFkMWIzNTItMTdjZC00Njc4LWFiNzEtZDM1NDlhYjNiNjFh

https://docs.google.com/open?id=0B95LjMhGv-qmMjhiNmU3ZTYtZDA1ZC00ZjBlLTkwY2MtOWViN2M3ZTZiNzFj
 
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Dlarrivee

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I'm not interested in fishing through documents to prove a point.

We all know it isn't done properly, it's simply speculative to come to some conclusion that it "will work because"... It doesn't meet any code I've ever read.
 

blackm3sedan

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I'm not interested in fishing through documents to prove a point.

We all know it isn't done properly, it's simply speculative to come to some conclusion that it "will work because"... It doesn't meet any code I've ever read.

I never asked you specifically to fish through all 3 pages of the plumbing trap code. I provided the code in case someone wanted to point to it and say that it specifically is not done per this statement in the code.

I don't believe that 'we' know it isn't done properly. My licensed plumber and my inspector believe that it is done per code. I provided evidence that the trap for the tub is still being vented and I don't believe anyone has proven otherwise. I'm not saying that it is the best way, but I don't think it violates any part of the plumbing code.

I also don't believe the laws of physics are 'simply speculative'. I would bet that any properly written code is based on them.

Your contribution to this thread has been invaluable. Thank you.
 
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