Toilet Vent Loop Suction Breaker Device

[passingas]

I am trying to devise something that will allow air into a toilet line when the toilet is flushed (the vent that should have been put in the first place), but then closes to keep the odors contained (I have imagined a backwards, spring loaded check valve, but this is a 4" sewer line). There is only one toilet on this line, going to its own septic tank. I would expect a vent problem with two different toilets on the same tank without a proper vent. About 15 seconds after it is initially flushed, the air in the line draws the bowl water level down and it gurgles and belches again. It works fine (no odors), just annoying. Any engineer types out there with a recommendation? Again, apologies to Crossy....Thanks in advance.

[passingas]

So this is like a by-pass sort of assembly? It doesn't vent out to atmosphere? It would take some digging up to do it, but I think I know what you are talking about. The 25.4 mm (1") line would tee off the 4" sewer line, 90 it towards the other end and then the same thing near where it empties into the septic...90 return to a tee into the 4". Would resemble a handle...it that right? Hmmmm.....I will look at it again and see exactly what all that would entail. Thanks for the idea, I appreciate it. pg

[bankruatsteve]

Again, I'm guessing you have a full septic or a clogged pipe. I don't think venting would help either of those - but I don't know, just my thoughts.

[Khonwan]

Why not simply put a T-junction on your sewage pipe at any visible point and extend a pipe to above your roof eaves; a clamp-type T (reducing 4” to at least ½”; I’d use 1”) would likely be easiest to install and only requires a suitable hole to be drilled into the 4” pipe. You shouldn’t experience any smell if this vent pipe is extended to above the eaves. Although I’ve never experienced it, I would consider an unvented septic tank to be an explosion risk (methane build up).

A full septic tank or partially clogged pipe could also cause the symptoms you’ve described but I still believe you should vent the tank.

Caveat: I’m not a plumber but I do all my own plumbing.

[passingas]

Thanks for all of the replies....first of all, the septic tank has been pumped out (had my fingers crossed on this one, hoping it would take care of the problem, but no....), and secondly I can not get a real vent to atmosphere apperati in at this point. I would have to do a by-pass type of idea. And then that would entail a lot of digging, but that's just what it will take. I think that would alleviate the problem. Again, it doesn't emit foul odors, only that annoying gurgle and then belching sound. I will just have to turn up the radio, eh? Again, thanks for all the input....pg

[bbradsby]

BEst is to retrofit a vent thru roof, but there are one-way valves on the market already. Theyre not accepted by US Code, FWIW. If your upstream toilet is gurgling, then it is acting as the one-way valve you desire. If the VTR is too painful to consider, maybe just install a 3" PVC running trap upstream of that toilet and install a trap primer so it never runs dry, and you have access so you can inspect it.

I think the methane explosion comment is 'overblown' LOL... because the septic tank should have a T fitting at its head that forms a gas trap/stop so no methane from the tank (the methane digester in the system) should have a path to the pipes upstream. There should be nothing sitting in the pipes to degrade and form any dangerous levels of methane, and basic gas dissipation via a 2" or 2 1/2" vent thru roof should easily keep it from getting to a dangerous level.

I do like the closed-loop idea, and if you have a 4" pipe serving the toilets, then it should be big enough to circulate air internally to balance pressure as the water flows through it. Make sure there are no clogs, tree roots, obstructions or low spots in the pipe run that will hold water and constrict the airflow. Underground sections of pipe are most susceptible.

Edited February 9, 2013 by bbradsby

[Khonwan]

Arjen, not looking for a keyboard fight but I cannot agree with you. I’ve spent a couple of hours reading on the subject due to your reply and can find nothing to support your view – every source indicates the need for a simple air vent as per these examples:

“A septic tank sewage system naturally produces methane and hydrogen sulphide gases (caused by bacteria breaking down the organic material in the wastewater). These gases smell, are dangerous, and are 'greenhouse gases' which are 21 times more polluting than carbon dioxide. Sinks and baths, therefore, have loops of pipe called P-traps that hold water in the lower loop and block the septic tanks gases from flowing back into the house. The gases flow up a ventilation or soil vent pipe instead -- if you look at any house, you will see one or more vent pipes going up the side of the house or poking through the roof. There should also be a vent pipe fitted on the outlet side of the tank.” (http://www.wte-ltd.co.uk/design.html - well worth viewing for anyone building their own septic tank).

“A vent pipe is required to allow the gas, formed in the septic tank by breakdown of excreta, to escape. The vent pipe can be installed on the sewer pipe running from the house to the septic tank, using a 100 millimetre diameter PVC "T" and a PVC reduction from the 100 millimetre diameter sewer size to 50 millimetres in diameter. The vent pipe layout is shown in Figure 7. The vent pipe should be 50 millimetres in diameter, reach roughly half a metre above the top of the house and have a fly screen covering the end.” (http://www.who.int/water_sanitation_health/hygiene/emergencies/fs3_9.pdf - World Health Organization).

If you still do not agree with me, I’d be pleased if you could support your view via any online credible source.

Bbradsby: “I think the methane explosion comment is 'overblown' LOL <snip> and basic gas dissipation via a 2" or 2 1/2" vent thru roof should easily keep it from getting to a dangerous level.” Of course there is no methane danger if it is vented – that’s exactly what I advised. As to your silly “LOL” comment that only serves to flame, go do some research rather than relying on your own opinion. As only one example of many, “Ventilation is essential due to the gases produced by the decomposing organic matter. If no ventilation is present, the septic tank will soon become an explosive environment. One should also bear in mind that in a confined environment like a septic tank, Methane can become an asphyxiate which kills you in seconds.” (http://www.wte-ltd.co.uk/septic_tank_dangers.html). Please do note, “…an explosive environment.”

I see that the US code also insists on an open vent: “… one fresh air vent per structure is required in the United States, especially when used with a septic system.” (http://www.toolbase.org/Technology-Inventory/Plumbing/air-admittance-valves)

The only error I made in my post was to suggest a minimum vent diameter of ½”; this is common upcountry in Thailand though I built my house with a 2” vent (which was simply a guess 17 years ago by me). I would guess that even a ½” is better than nothing.

[passingas]

This is the culprit...I had to slope the initial part rather steeply, to where the rest of the run, which is straight as an arrow and the recommended slope 1/4" per foot....would be concealed in the plumbing chase to the septic tank (this tank got arbitrarily put where it is...more or less, elevation wise, anyway). I have room at this end to do something, that is why I wish I could retrofit a backwards check valve to atmosphere. By the way, I put clean outs on all the long, straight runs and that could be what is causing the problem. I will have to make a wrench to open the threaded cap to inspect the run after that rather steep drop. This very well could be why it is gurgling and belching. I will do this tomorrow as I now have some free time. Thanks again to all for all the input....pg

[bankruatsteve]

Yeah. That looks great to me. So, if you flush the toilet and look into the septic tank, is there full flow there or just a trickle? Looks like plenty of places to add a vent if you really want one - but I don't think that's going to help anything. Guessing you will find the problem when you get into your clean out. ??

[bbradsby]

... I’ve spent a couple of hours reading on the subject due to your reply and can find nothing to support your view – every source indicates the need for a simple air vent as per these examples:

“A septic tank sewage system naturally produces methane and hydrogen sulphide gases (caused by bacteria breaking down the organic material in the wastewater). These gases smell, are dangerous, and are 'greenhouse gases' which are 21 times more polluting than carbon dioxide. Sinks and baths, therefore, have loops of pipe called P-traps that hold water in the lower loop and block the septic tanks gases from flowing back into the house. The gases flow up a ventilation or soil vent pipe instead -- if you look at any house, you will see one or more vent pipes going up the side of the house or poking through the roof. There should also be a vent pipe fitted on the outlet side of the tank.” (http://www.wte-ltd.co.uk/design.html - well worth viewing for anyone building their own septic tank).

“A vent pipe is required to allow the gas, formed in the septic tank by breakdown of excreta, to escape. The vent pipe can be installed on the sewer pipe running from the house to the septic tank, using a 100 millimetre diameter PVC "T" and a PVC reduction from the 100 millimetre diameter sewer size to 50 millimetres in diameter. The vent pipe layout is shown in Figure 7. The vent pipe should be 50 millimetres in diameter, reach roughly half a metre above the top of the house and have a fly screen covering the end.” (http://www.who.int/w...ncies/fs3_9.pdf - World Health Organization).

If you still do not agree with me, I’d be pleased if you could support your view via any online credible source.

Bbradsby: “I think the methane explosion comment is 'overblown' LOL <snip> and basic gas dissipation via a 2" or 2 1/2" vent thru roof should easily keep it from getting to a dangerous level.” Of course there is no methane danger if it is vented – that’s exactly what I advised. As to your silly “LOL” comment that only serves to flame, go do some research rather than relying on your own opinion. As only one example of many, “Ventilation is essential due to the gases produced by the decomposing organic matter. If no ventilation is present, the septic tank will soon become an explosive environment. One should also bear in mind that in a confined environment like a septic tank, Methane can become an asphyxiate which kills you in seconds.” (http://www.wte-ltd.c...nk_dangers.html). Please do note, “…an explosive environment.”

Congrats, you passed your introductory coursework for your online degree in the Use of Google! YES, we actually agree, your Googled opinion and my professional opinion, that venting is the best practice. But the lack of venting in residences is not an explosion risk, sorry. Your posted links were a joke actually. I have the California Plumbing Code on my laptop in pdf format... so if you require some real information, not your pompous off- gassing, just give me your credit card number and I'll send you my billing rates.

However, the rest of us are trying to help the OP out with some out-of-box thinking. Now then:

To the OP, one of your pix show far too much slope, which tends to leave the solid matter behind as the water speeds away. This may in fact be the root of your problem - an obstructed pipe, where you'd least expect it, that is siphoning your bowl trap. Slope should be 1/8" to 1/2" per foot, even as 1/4" is the figure to use. I don't recommend the 1/8", as it's difficult to achieve in the field. Snake the toilet, and see if that doesnt solve your problem. How many meters/feet away from that drain pipe is the closest vent stack?

If you can't manage/stand another vent up through the roof (VTR in professional parlance), the "Island Vent" - as in, a kitchen sink installed on an island in the middle of the kitchen, away from any walls - is what I suggested in my first post to you. It uses the branch drain as the vent, via being oversized enough to let the gas pressure equalize within the pipe. Just have a VTR as close by as possible, and the one on the tank doesn't count.

[BB1955]

I have an issue now Im looking at on a new house build. They have put a vent pipe into the top of my septic tank run it along the ground and stubbed it up near the inside of my perimter wall Im not even sure my fill will cover the pipe ....

[bankruatsteve]

bbradsby: I have a snake and have tried to get it through the toilet but have never been successful. Is that a toilet thing? Or a technique thing? Anyway... my experience is the problem is almost always somewhere else.

[Khonwan]

Good, bbradsby – not Laughing Out Loud now. World Health Organization is a joke is it? I’ll leave it to other readers to decide for themselves. As for your silly comment on your possession of the California Plumbing Code – it is available for free online here: http://www.iapmo.org...umbingCode.aspx

I used Google to back up my claims and credited the sources. Perhaps you would rather I use Bing? Or would you prefer that I try to find a reference library here to photocopy credible sources for your perusal? Anyone can call themselves a professional on a forum like this – if you are a professional plumber, it doesn’t mean that you are a competent one. One of the benefits of the Internet is that so called professionals like you can be called out.

Thinking outside the box? I’ve another catchphrase for you: KISS (keep it simple stupid).

Edited February 12, 2013 by Khonwan

[Crossy]

I have an issue now Im looking at on a new house build. They have put a vent pipe into the top of my septic tank run it along the ground and stubbed it up near the inside of my perimter wall Im not even sure my fill will cover the pipe ....

You should also have a vent at the far end of the toilet pipe, it's this which seems to be missing in our OPs installation causing the loo to gurgle.

[Morakot]

This is the culprit...I had to slope the initial part rather steeply, to where the rest of the run, which is straight as an arrow and the recommended slope 1/4" per foot....would be concealed in the plumbing chase to the septic tank (this tank got arbitrarily put where it is...more or less, elevation wise, anyway). I have room at this end to do something, that is why I wish I could retrofit a backwards check valve to atmosphere. By the way, I put clean outs on all the long, straight runs and that could be what is causing the problem. I will have to make a wrench to open the threaded cap to inspect the run after that rather steep drop. This very well could be why it is gurgling and belching. I will do this tomorrow as I now have some free time. Thanks again to all for all the input....pg

I'm not a plumber but it does not look right. I have heard a rule of thumb that you either have (1) vertical pipes or (2) horizontal pipes pitched about 3-5 cm per meter. The reason is that faecal matter will drain its self "dry" on steep slops with the liquid running off while solid matter will be depleted of "transport lubrication". It could lead to excessive noise, unusual movements and even blockage. Like wise no pitch or to little would of course also cause blockage.

Edited February 13, 2013 by Morakot

[Morakot]

@morakot

No Pitch is no problem. 30-50mm/meter is far to much.Recommendation is 1mm/meter.

OK, I see what about too much pitch? Thanks!

[passingas]

There is too much initial pitch, for sure, but had no other choice. I just got the 4" PVC plug unscrewed out of the adaptor of the end of my sanitary wye, and the line where it comes into that transition is not clogged at all! I must say I was a wee bit surprized....and there is a vent on the septic tank itself which is only a 1" vent, but that is how it was made. I am now suspecting that is the issue. I flushed the toilet with the plug out to see how it did, and it flushed without incident and no back water on me, thank goodness for all of the slope. It drained down the line like it was supposed to, without any gurgling and belching, but that was probably due to the fact that the plug was out and had atmosphere equalization. I will now focus on the tank vent itself, as it did not do this the first year of use. I do realize that a loop vent would take care of the issue, but that would be a major, major undertaking. Thanks again to all for all of your input, comments and other replies.....pg

[passingas]

BB1955...come out of the tank vent hole (it should be threaded if it is a plastic tank) with a threaded 90. Use the white teflon pipe tape and wrap it so you don't unwrap it as you thread the fitting into the tank. It might have to be redone altogether if someone that didn't know what they were doing, did it. That will get it as close as it can get to running laterally at its lowest point. I have seen christmas trees and rocket ship looking stuff for adapting different sizes, especially here in LOS. Mine is done with a threaded 90 and I made the fill cover it...however, you don't want any bellies in it. If anything you would want it to drain back towards the tank if it got moisture in it, ie rain. Use a tee on the last upright piece and you have a pretty good rain deflector. That way it will vent as it is supposed to...I am now thinking that is my problem....pg

[Mrjlh]

Methane is NOT heavier than AIR! It is LIGHTER. CH4 weight index is 16. Index of Air is 28. Plugging the vent creates an explosive condition. So you want to vent it out and away from from the source and as high as possible. You can argue all you want. But what you are planing is purely stupid and creates a dangerous situation.