I have this setup in my crawlspace. I get a sewer smell coming out of the trap, I think even when I have primed it.
Any ideas?
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Replies
Blue
What drains into that ?
And how did your door project turn out?
thanks.
Inputs
Draining into that is condensate from an HRV, the prv output from a ele hotwater tank, and the drain for the sprinkler system or flow test.
Door project is kind of sitting there still sadly. It looks like in the winter my moisture is too high as I tend to avoid using the HRV when my neigbor is burning wood as the HRV ends up sucking the smoke into the house and I have a baby in the house. Since the moisture ends up being high it condenses on the inside of the door and pools onto the oak threshold. My MDF window sills are also cauliflowering and molding... I've got a dehumidifier which seems to help, I need to get another one as well. Once I get the moisture issue sorted then I'll look at replacing the sills (20 of them) and the deck door threshold. The vinyl vane replacement seems to prevent moisture from coming in via the jamb gap. I am still not sure if even with the dehumidifier that no mositure will condensate on the interior surface of the door so I'll probably have to wait until next winter again to make sure the moisture is dealt with before I put any work into the threshold. Sigh.
Is it legal to run the the prv discharge like that?
All the US plumbing codes I have read forbid running the PRV to a sewer drain. The PRV is supposed to discharge to a point readily visible to occupants, in case it leaks, and requires an air gap before it can drain to a sewer. That installation is just sloppy in my view, (now I know where my drugoid little brother moved to).
How close is the nearest vent? That setup seems likely to siphon dry, unless there's a vent hidden in the wall.
Nearest vent is probably 20'
This is the orignal work by the plumber and passed inspection. Though the plumber was useless so there could be something wrong.
I haven't looked at the venting code in a while but wouldn't this be fine as the pipe is 4" going into a 4" and should be able to be vented via wet venting as long as the arm isn't longer than the critical length? The question I had was also what angle should the roll of the Y be for the trap connection, I seem to remember this might be an important detail. Right now it appears pretty flat.
I wrongly assumed that the picture was showing 2" pipes. I agree with you that 4" piping should easily work as a wet-vented system.
As for the angle of the wye branch (rolling the branch up), that would defeat, or at least impede the way a wet vent is designed to work. It's should be left flat the way it is.
The reason for this is that horizontal wet venting depends on having air circulation in the top half of the horizontal line and the bottom half being for water flow. Codes are written to size drainage pipes so that the design load only fills the horizontal pipe half full. Modern water-saving fixtures have even lower flow rates than when the codes were originally written.
So, whenever you roll a wye branch up on a line that serves as a horizontal wet vent, you create potential for a "curtain" of water to block off the top half of the line that is supposed to be acting as a path for air circulation.
Now, I am baffled as to why you are getting any sewer gas odors from that trap. None of the drains that enter it would ever produce the kind of flow that would flush a 4" trap, and it seems very unlikely to me that the upstream flow would be enough to fill the 4" line enough so as to create a suction on the trap arm.
wet venting
This is what I usually look at for plumbing vent related things.... so in my case I'd say that the 4" trap connected to the main horizontal sewer line is similar to the shower connection on #6 at the end. In the diagram you can see that the Y is angled at what looks like 45 degrees. The roll of the Y for a wet vent would actually apply to the pipe that is supplying the venting which is actually upstream of the trap and according to the orientation of waste and vent connections on page 3 it just must connect up at less than 45 degree angle.
http://www.jlconline.com/Images/Plumbing%20Venting%20Explained_tcm96-1157318.pdf
Let me see if I can draw the plumbing for my house.... it won't be pretty but might be easier to see once you can tell the relative positioning of the vents.
I have images for all plumbing connections in my house so I can provide more detail on any area of the diagram once I draw it.
Thanks for the response and dialog. Helpful to walk through this.
My hopefully understandable plumbing diagram
Let me know if you need more details around any part of this or if something isn't clear.
If that's the layout then your trap is unvented. That's not even a wet vent. A wet vent must be vertical. Your trap hooks directly to a horizontal waste with no vent. Install the air admittance valve.
The uniform plumbing code doesn't allow horizontal wet vents
but that isn't to say that this is unvented it is horizontally wet vented. The only thing required to "vent" something is for air to follow water (where it isn't pulling the air from in front of the trap). So in this case the 4" trap as long as it is less than 12 feet from the horizontal 4" line and as long as the of the 4" Y both upstream and to the trap have air then this is vented (assuming no water plug upstream b/t the wet vent pipes and the dry vent pipe.
If you look at the Cauldwell document under wet venting similar setups to mine and certainly horizontally wet vented setups are diagramed and described as wet vented.
look at your diagram
Your trap discharges into a horizontal waste line. One level above that (not allowed) discharging into the same waste line is a toilet (not allowed), a sink and a laundry. Two levels above that (not allowed) discharging into the same waste line is a sink and a dish washer (neither allowed). Presumably somewhere there is a tub or a shower at least one level above (not perm. Wet venting is only allowed between bathroom units on the same level.
You ask why your trap stinks. It stinks because you installation stinks and isn't even close to code. What did your plumbing inspector say? Oh, you didn't get permits. We all knew that.
If you want to stop the stink, install the AAV and seal the top of the trap where the small pipes enter it.
Bluegoat's profile shows he's from Vancouver, BC, whose plmg code is based, not on the UPC, but on the Canada National Plmg Code, so certain provisions therein may be considerably different from the UPC, just as the IPC here in the US is different from the UPC, especially as regards horizontal wet venting. Which is not to suggest that his job meets all the requirements of the code he's under, but the job may well be in compliance with the exception of the 4" p-trap he's having trouble with.
One of his earlier posts indicated that the job was inspected, so he most likely did have a permit.
Your suggestion that he seal the top of the trap where the small pipes enter it would be a code violation of every code I know of, including the UPC that you have been referring to.
All done by a licensed plumber and all permited and inspected
I hired a design/build firm to build my house. They hired the plumbing company. I can guarantee that there were permits and it was inspected at various times by the plumbing inspector at various time. I can't guarantee that this particular trap was inspected as the hwt location changed due to height but I think it is very likely that it was inspected or at least signed off as having been inspected. When the plumbing is in a crawl space without a slab and puddles of water over insulation I can't guarantee that the plumber inspector went down and viewed everything with the level of detail required. I never personally talked to the plumbing inspector, I am not even sure if the builder would have, generally the plumber pulls the plumbing permit and goes through it with the inspector.
You are right I did forget to put the tub into the diagram, as you'd imagine it dumps in just slightly upstream of the toilet.
Now in terms of levels I am not sure if you consider the crawl and the mainfloor different levels after all the trap for the shower is in the crawl. Would you then consider the shower as being in the crawl level?
I am going to review the city building code and take a look at what it says about wet venting. I do appreciate the discussion even if you do jump to conclusions.
There are two possible ways for that trap to empty: one, by a flushing action that could be created by high-volume flow from one of the pipes that empties into the short standpipe, like maybe the discharge from a water softener; the other possibility is that the drain line (where the wye connects the trap arm) could be siphoning the trap when the flow in the drain line is rushing past the wye.
There should have been a vent take-off between the trap and the wye.
As it is now, the easiest fix would be to change out the p-trap for a deep seal trap. You can fabricate one yourself by using three 90-degree bends that you connect with short pieces of pipe so that you end up with a much deeper seal of water that stands in the trap, say at least 4", compared to the 2" that you have now.
This extra depth will resist both flushing and siphoning much better than your current setup.
I'd guess siphoning as the input into the trap are infrequent
Shouldn't wet venting handle this?
I've never heard of a deep seal trap - I'll look into that.
Thanks !
I agree that the inflow to the 4" trap is unlikely to cause the trap to lose its seal, and that siphoning from the flow in the main line is the probable cause.
in that case, the AAV would help, and certainly not do any harm.
Whatever you end up finding, please let us know what happens.
Plumbing Model
Will do. I am thinking of just getting rid of the trap.
Here is a better diagram of the complete WDV - though I could only use 90 Ys in the model so while it is close to accurate the angle on the tees are off.
Thanks for the help everyone !
Where is the problem trap, and where is the basement you previously mentioned?
No basement in this place just a crawl.
The problem trap is the one by the exit of the sewer from the house - on the far right of the diagram.
Well, you said "The basement
Well, you said "The basement is lower than the storm sump well so this water mixed with sewer and sent water back up the floor drains". Has me confused -- how are floor drains lower than the trap in the crawl?
Maybe you missed the title of the reply to that one:
"The sewer backup occur in a house I used to live in..."
Then I don't see how that applied to the current situation.
It just applied as you expected a slow blockage whereas the only blockage I've had experience with and would push my efforts to preventing is a full blockage. Just that ideally the lowest point is the bathtub drain to provide some form of mitigation.
I had a plumber out for a different issue and ran this one by him. He suggested that the bathroom group and the toto toilet in particular could be overwealming the bathroom group vent. He thought it possible that debris from trees or wasp nest may be obstructing the dry vent for the sink which wet vents the bathroom group. He said another possiblity was that the dry vent has a belly somewhere and debris could have accumulated there.
He says that he runs all his bathrooms at 2" and that he thought the picture I showed him looked like 1 1/2" though I checked and the sink drain is 2". I might auger up from the sink cleanout and see if hit any resistance.... i think it would be hard to auger down and hit the horizontal dry vent run off the main stack. There was a 150 yo douglass fir tree that would drop a lot of needles onto the roof... not sure how likely it is they would have gotten into the horizontal dry vent line off the main stack though... the wasp theory could make sense though...
I still plan on trying to eliminate the trap... just might be a while before I get to it - haha.
Vent valve
Try an air admitance valve between the trap and the wall.
An AAV only protects from siphoning by downstream pipes and fixtures; it won't do anything to prevent flushing of the trap by one of the lines dumping into the trap.
aav
View Image
Air admittance valves (AAVs) are pressure-activated, one-way mechanical vents, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations. A discharge of wastewater causes the AAV to open, releasing the vacuum and allowing air to enter plumbing vent pipe for proper drainage. Otherwise, the valve remains closed, preventing the escape of sewer gas and maintaining the trap seal. Using AAVs can significantly reduce the amount of venting materials needed in a plumbing system, increase plumbing labor efficiency, allow greater flexibility in the layout of plumbing fixtures, and reduce long-term maintenance problems associated with conventional vent stack roofing penetrations.
Standard plumbing systems use water trap seals to perform the critical function of preventing sewer gas from emanating into living areas, with fresh air pipe venting commonly used to prevent siphoning of traps. Although this method is simple and reliable, it requires each plumbing fixture to have a lateral return vent that passes through wall studs to a central stack, or to have its own vertical vent that passes through the wall, ceiling, attic, and roof. Air Admittance Valves are mechanical devices designed to maintain trap seals without the need for additional vent piping. They are one-way valves that open only under negative pressure (created when a toilet is flushed or a drain stopper is opened). When the water flow stops, gravity closes the valve, preventing the escape of sewer gasses under conditions of equal or positive pressure.
AAVs are typically made from polyvinyl chloride (PVC) plastic materials with ethylene propylene diene monomer (EPDM) rubber valve diaphragms. Valves come in two sizes: one for fixture venting and a larger size for system venting. The valves fit standard diameter pipes, ranging from 1-1/4 to 4 inches. Screening protects the valves from foreign objects and vermin. ASSE (American Society of Sanitary Engineers) standards require that AAVs be tested to reliably open and close a minimum of 500,000 times, (estimated to be at least 30 years of use) with no emanation of sewer gas. Some manufacturers claim their units are tested for up to 1.5 million cycles, or at least 80 years of use. Air Admittance Valves have been effectively used in Europe for more than two decades. U.S. manufacturers offer warranties that range from 20 years to lifetime.
Right--AAV's are designed to relieve siphoning action only--they do not relieve positive pressures in the system because they are essentially one-way air valves--they let air in but not out.
That's why codes that allow them also require that the system for each floor must also have a vent piped out to the atmosphere.
Just how is "flushing of the
Just how is "flushing of the trap" going to drain it, unless there is siphoining?
(The AAV would likely fix the problem, and would be the simplest fix.)
I purposely used the term "flushing" to describe what could happen with the pressured discharge of a water softener drain into a 2" trap, which I mistakenly assumed was the trap size. Similar to how a blowout urinal evacuates its trap, but the urinal valve refills the trap with reduced flow.
AAV would likely work....
but I think this setup should still work without an AAV via wet venting... ideally I'd like to know why it isn't working.
Wet vent.
A wet vent uses a vent for one fixture as the waste line for another fixture. The most common wet vent is a lav draining into a toilet vent in the same bathroom. Wet venting is not permitted between stories. If you have a fixture draining into the vent of a lower fixture enough flow can create a suction and pull the water out of the trap of the lower fixture. My guess is that the vent for your trap is a waste line for a fixture above.
True the wet vent would be from the main floor or top floor
Are you sure you can't wet vent between stories? I have a hard time interpreting what Cauldwell means when he says "Both horiz and vert pipes (limited to one story height) can be wet vented. My place is 1.5 stories with a crawl. I only have one vent through the roof and it is about 15' off the ground. Why would this be limited to 1 story? I suppose the point is that you shouldn't have so many things draining into your wet vent that a water plug could form and cut off the wet venting... and this is easier to occur if you have things from different stories draining into it?
Not looking at just the plumbing...whats the deal with the foundation? It looks like part of the foundation to the left of the trap has dropped 1/2 - 3/4 of an inch compared to the other section.
Foundation is fine...
The rigid foam install just makes it look funky. This was installed against the wall then the slab was poured and then the gap between it and the joists was filled with pieces.
Thanks for the thought though !
It occurs to me that it would probably be wise for the OP to check that all the joints in the area are actually glued up. It wouldn't be the first time that a joint was dry fit and never glued.
aside from a pressure test how would I determine if the joints..
are glued. I put my face over the trap and this is where the smell was coming from so I do know that is the source.
Have you poured water in the trap to see if that eliminates the odor, at least temporarily?
Right so my first thought was that the trap had just evaporated
But I had poured enough water to hear the water start flowing a couple weeks before at least and I am pretty sure I had done it again recently... so I'd be surprised if it all evaporated. I think re-filling the trap did eliminate the smell at least temporarily.
If the smell goes away when you fill the trap that's pretty good evidence that the trap is being siphoned dry. Of course, one would expect that the various drains feeding it would refil the trap, but they may not be regular enough for the flushing toilets and emptying tubs that will do the sucking.
If it were purely evaporation you could pour several ounces of mineral oil into the trap to slow evaporation. But that won't help with siphoning.
Consider this
Bluegoat,
First of all I apologize for conclusion jumping. I'm like a kangaroo.
Ask your plumber why the trap stinks.
Ask yourself, if your house sewer plugs up, how much sewage from the house above will flow into your crawl space through this trap before you notice it? Seems like a disaster waiting to happen.
What is purpose of this trap? Can it be eliminated?
Definitely good things to consider
The backup problem is something I am worried about as well as I've dealt with backups before. Fortunately all the plumbing from my house out to the main is 2 years old and the chance should be quite a bit smaller. I was thinking about building some kind of containment below the trap with a watts water sensor such that if it did start to overflow I would at least have some kind of alarm going off and as long as the main wasn't backing into the house then the volume of the container would hold at least say three bathtubs worth of water.....
Eliminating the trap would be a better solution, I'd have to re-pipe the sprinkler drain (outside maybe ), re-pipe the hwt prv output (maybe outside again), re-pipe the hrv condensate pump drain line somewhere.... I'd have to look up the lift on the pump, the tubing is 1/2" clear tubing. So I think all of these are do-able... the crawl is almost 4' underground so I am not sure if I'd need to dig a box so you could actually see the pipes outputing... or what the code would call for in that respect. I could also possibly plumb them both up to the first floor and then into say the laundry drain... I don't know if the 2" trap for laundry would handle the sprinkler flow and the prv flow or what code would say it needs to handle. Both dumping at once with the laundry draining. I am not sure if they used a 4" trap because it was easier than decreasing to a 2". Really it is close enough to the main horiz line that it would horiz wet vent with pretty much any size (functionally anyway this violates the 2 bathroom group only wet vent rule but it is just a seldom used trap). Probably putting the sprinkler drain higher than the lowest sprinkler wouldn't make a lot of sense... tho I could maybe just have it point down and require using a bucket to drain it (again not sure what code would say).
AAV would be the least work but doesn't prevent a sewer backup. If I include the work to make some kind of containment for the sewer (nasty and not ideal) maybe re-doing those lines somewhere would be a similar amount of work....
I don't think the plumbing company the builder used is still employeed by the builder and I believe the plumber who did the work for the plumbing company also no longer works for that company. I could ask the builder, I could ask the company the builder used, but really shouldn't one of those two have set this up for no trap in the first place. It sounds like it could have been avoided and probably wouldn't have been too much more work when nothing is finished. Should I trust either to come out and fix this problem for me? The plumber put a 2.5" deep hole into the middle of a 4 member 2x10 beam that supports one of the walls that runs to the roof in addition to installing the bath sink with the overflow leaking into the cabinet, the one piece rainshower system unlevel, unplumb and too far away from the finished surface for the eschucton plates to cover the course thread of the handle nipples, and put this trap without the vertical piece coming out... which if you look at it and the trap did fill up it would just flow into the crawl sooner than the pipe it connects to.
I'd prefer to hire someone else or fix this myself then call either parties back. I do like the idea of fully eliminating the trap from the mix. Just need to figure out the details.
You could easily raise the pipe stub up another 4" or so, which would reduce the likelihood of an overflow by at least 50%. You might be able to install a backflow valve, but those tend to stick, so the thing could flood when the PRV trips or whatever.
Would help...
I think the ideal thing to prevent or minimize a sewer backup is to have the bathtub drain as the lowest point in the house, that way if the sewer comes in it just fills the bathtub... adding 4" to this trap will just delay it overflowing by 4" and it would still be the lowest point. I've previous put one way fittings on floor drains to ensure that the tub is the lowest and then you hope that the wax seal on the toilet is strong enough to prevent backflow and the tub is the only point of entry.
My thinking is that complete blockage is fairly rare -- more common is sluggish flow, and the extra 4" can make quite a difference in that case.
I have experienced complete blockage so can't be that uncommon
In the case I experience it was compounded by rain water. The perimeter and rain drain went into a sump, the sump ideally feeds into a storm drain but in this case the city didn't have a storm so the sewer from the house and the storm from the sump join with a Y and enter the city portion which was 1930 clay. The city portion clogged from roots and then probably toilet paper. A giant rain storm came along and when the water couldn't exit at the Y it went back up the sewer as there was a pressure column of water in the storm sump. The basement is lower than the storm sump well so this water mixed with sewer and sent water back up the floor drains, tub and possibly at the toilet flange. While this water was likely 90% rain water it was mixed with sewer as it traveled up the sewer pipe.
Kind of a crappy deal as the blockage was on the city side which you can't touch. You can pay 16k to have the city redo their side.
So you have both a basement and a crawl? What is the height relationship between the two?
(It's illegal to dump storm water (or footer drain water) into the sanitary sewers where we live. If there's no storm sewer then the rainwater must be dumped on the surface.)
The sewer backup occur in a house I used to live in...
Might be illegal where you live but when you get 4' of rain a year you can't be dumping it on the surface. It is against code to tie them in. It just happens that is how the city does the connection here when they haven't gotten around to separating the two systems. There is a 100 year plan in place to separate them ( I think that is how long they figure it will take before the city is fully upgraded, not too surprising when it costs 16k for them to do their 5' sections under the sidewalk ).
Sewer was backing up / Can I turn off the primer in shutoff?
Turns out after I removed all the pipes dumping into the trap I could see that the sewer had been backing up a little into the trap. Some sludge on the portions of pipes that were decending into it. Also It looks like a few cups of sewer water did come out of the trap into the crawl - fortunately I didn't have anything near this area so clean up isn't too bad.
Guess that explains the smell... I guess it was a partial blockage and only went the capacity of the blocked area was surpassed did it start to back up and only small amounts but enough to have sewage go into the trap and start causing a smell.
At least I know what the problem was now. I still have to re-route all of the things that were feeding into the trap and seal the trap but at least for the moment it doesn't appear to be backing up anymore.
One of the pipes feeding into the trap seems to be a priming mechanism build into a 3/4" water shut off. The part where the water comes out of the shutoff and into the trap has a threaded nut, if I turn the threaded nut will it slow down/stop the prmining action?
You need to be careful that you don't create a cross-connection from that line that originates at the 3/4" shutoff. Since that line is connected to the potable water, you wouldn't want to have its outlet enter the drain system in a way that could possibly allow contamination when the sewer might be blocked. The proper way is to drain that line is by means of an airgap or an approved backflow preventer.
A photo would help to identify whether it is actually a trap primer that was intended to prevent the trap from drying out or something else.
And, thanks for following up on your story.Sewer gas smells can be one of the hardest things to figure out in plumbing.
trap primer / air gap
Here is the image of the trap primer, I've disconnected it from priming the trap.
I am familar with an air gap but I guess the plumber who installed it wasn't. Given there was sludge around the output of the trap primer, how concerned should I be that some pathogen has entered my hotwater system? I could increase the tank temperature to maximum leave it like that for 24 hours and then put it back down to normal? Suggestions?
I don't recognize that specific device, but it appears to be a listed and approved trap primer. If so, that means that it would not need an airgap since trap primers are designed to be directly connected to the drain. In other words, they are, in themselves, a backflow prevention device.
I don't think you need to worry at all about having any pathogens in your system as a result of that primer or its past connection to the drain.
Sumppump
Easy solution is to put the stuff that drains into the trap into a receptical and pump that into a closed waste pipe. A check valve will prevent backflow. This exactly what you'd do if you had a fixture that was too low to drain by gravity. This may not be the cheapest solution but it's the easiest.
Except you probably can't legally do that with a PRV drain, and a standard condensate pump could easily be overwhelmed by the sprinkler drain.
That's good news !
Thanks for looking at it !
Any idea if I should just be able to crank the hex nut and stop the priming device from letting water out or if I'd just need to remove the primer entirely?
I'm not familiar with that particular device, but if you can shut off the flow to the primer line while still allowing flow to the rest of the house, there would be no problem. You would only be losing the priming function, which is no longer needed if you have removed the trap that needed periodic priming to keep from drying out.